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open_toontown_panda3d/panda/src/doc/eggSyntax.txt

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THE PHILOSOPHY OF EGG FILES (vs. bam files)
Egg files are used by Panda3D to describe many properties of a scene:
simple geometry, including special effects and collision surfaces,
characters including skeletons, morphs, and multiple-joint
assignments, and character animation tables.
Egg files are designed to be the lingua franca of model manipulation
for Panda tools. A number of utilities are provided that read and
write egg files, for instance to convert to or from some other
modeling format, or to apply a transform or optimize vertices. The
egg file philosophy is to describe objects in an abstract way that
facilitates easy manipulation; thus, the format doesn't (usually)
include information such as polygon connectivity or triangle meshes.
Egg files are furthermore designed to be human-readable to help a
developer diagnose (and sometimes repair) problems. Also, the egg
syntax is always intended to be backward compatible with previous
versions, so that as the egg syntax is extended, old egg files will
continue to remain valid.
This is a different philosophy than Panda's bam file format, which is
a binary representation of a model and/or animation that is designed
to be loaded quickly and efficiently, and is strictly tied to a
particular version of Panda. The data in a bam file closely mirrors
the actual Panda structures that are used for rendering. Although an
effort is made to keep bam files backward compatible, occasionally
this is not possible and we must introduce a new bam file major
version.
Where egg files are used for model conversion and manipulation of
models, bam files are strictly used for loading models into Panda.
Although you can load an egg file directly, a bam file will be loaded
much more quickly.
Egg files might be generated by outside sources, and thus it makes
sense to document its syntax here. Bam files, on the other hand,
should only be generated by Panda3D, usually by the program egg2bam.
The exact specification of the bam file format, if you should need it,
is documented within the Panda3D code itself.
GENERAL EGG SYNTAX
Egg files consist of a series of sequential and hierarchically-nested
entries. In general, the syntax of each entry is:
<Entry-type> name { contents }
Where the name is optional (and in many cases, ignored anyway) and the
syntax of the contents is determined by the entry-type. The name (and
strings in general) may be either quoted with double quotes or
unquoted. Newlines are treated like any other whitespace, and case is
not significant. The angle brackets are literally a part of the entry
keyword. (Square brackets and ellipses in this document are used to
indicate optional pieces, and are not literally part of the syntax.)
The name field is always syntactically allowed between an entry
keyword and its opening brace, even if it will be ignored. In the
syntax lines given below, the name is not shown if it will be ignored.
Comments may be delimited using either the C++-style // ... or the
C-style /* ... */. C comments do not nest. There is also a <Comment>
entry type, of the form:
<Comment> { text }
<Comment> entries are slightly different, in that tools which read and
write egg files will preserve the text within <Comment> entries, but
they may not preserve comments delimited by // or /* */. Special
characters and keywords within a <Comment> entry should be quoted;
it's safest to quote the entire comment.
LOCAL INFORMATION ENTRIES
These nodes contain information relevant to the current level of
nesting only.
<Scalar> name { value }
<Char*> name { value }
Scalars can appear in various contexts. They are always optional,
and specify some attribute value relevant to the current context.
The scalar name is the name of the attribute; different attribute
names are meaningful in different contexts. The value is either a
numeric or a (quoted or unquoted) string value; the interpretation
as a number or as a string depends on the nature of the named
attribute. Because of a syntactic accident with the way the egg
syntax evolved, <Scalar> and <Char*> are lexically the same and both
can represent either a string or a number. <Char*> is being phased
out; it is suggested that new egg files use only <Scalar>.
GLOBAL INFORMATION ENTRIES
These nodes contain information relevant to the file as a whole. They
can be nested along with geometry nodes, but this nesting is
irrelevant and the only significant placement rule is that they should
appear before they are referenced.
<CoordinateSystem> { string }
This entry indicates the coordinate system used in the egg file; the
egg loader will automatically make a conversion if necessary. The
following strings are valid: Y-up, Z-up, Y-up-right, Z-up-right,
Y-up-left, or Z-up-left. (Y-up is the same as Y-up-right, and Z-up
is the same as Z-up-right.)
By convention, this entry should only appear at the beginning of the
file, although it is technically allowed anywhere. It is an error
to include more than one coordinate system entry in the same file.
If it is omitted, Y-up is assumed.
<Texture> name { filename [scalars] }
This describes a texture file that can be referenced later with
<TRef> { name }. It is not necessary to make a <Texture> entry for
each texture to be used; a texture may also be referenced directly
by the geometry via an abbreviated inline <Texture> entry, but a
separate <Texture> entry is the only way to specify anything other
than the default texture attributes.
If the filename is a relative path, the current egg file's directory
is searched first, and then the texture-path and model-path are
searched.
The following attributes are presently implemented for textures:
<Scalar> alpha-file { alpha-filename }
If this scalar is present, the texture file's alpha channel is
read in from the named image file (which should contain a
grayscale image), and the two images are combined into a single
two- or four-channel image internally. This is useful for loading
alpha channels along with image file formats like JPEG that don't
traditionally support alpha channels.
<Scalar> alpha-file-channel { channel }
This defines the channel that should be extracted from the file
named by alpha-file to determine the alpha channel for the
resulting channel. The default is 0, which means the grayscale
combination of r, g, b. Otherwise, this should be the 1-based
channel number, for instance 1, 2, or 3 for r, g, or b,
respectively, or 4 for the alpha channel of a four-component
image.
<Scalar> format { format-definition }
This defines the load format of the image file. The
format-definition is one of:
RGBA, RGBM, RGBA12, RGBA8, RGBA4,
RGB, RGB12, RGB8, RGB5, RGB332,
LUMINANCE_ALPHA,
RED, GREEN, BLUE, ALPHA, LUMINANCE
The formats whose names end in digits specifically request a
particular texel width. RGB12 and RGBA12 specify 48-bit texels
with or without alpha; RGB8 and RGBA8 specify 32-bit texels, and
RGB5 and RGBA4 specify 16-bit texels. RGB332 specifies 8-bit
texels.
The remaining formats are generic and specify only the semantic
meaning of the channels. The size of the texels is determined by
the width of the components in the image file. RGBA is the most
general; RGB is the same, but without any alpha channel. RGBM is
like RGBA, except that it requests only one bit of alpha, if the
graphics card can provide that, to leave more room for the RGB
components, which is especially important for older 16-bit
graphics cards (the "M" stands for "mask", as in a cutout).
The number of components of the image file should match the format
specified; if it does not, the egg loader will attempt to provide
the closest match that does.
<Scalar> compression { compression-mode }
Defines an explicit control over the real-time compression mode
applied to the texture. The various options are:
DEFAULT OFF ON
FXT1 DXT1 DXT2 DXT3 DXT4 DXT5
This controls the compression of the texture when it is loaded
into graphics memory, and has nothing to do with on-disk
compression such as JPEG. If this option is omitted or "DEFAULT",
then the texture compression is controlled by the
compressed-textures config variable. If it is "OFF", texture
compression is explicitly off for this texture regardless of the
setting of the config variable; if it is "ON", texture compression
is explicitly on, and a default compression algorithm supported by
the driver is selected. If any of the other options, it names the
specific compression algorithm to be used.
<Scalar> wrap { repeat-definition }
<Scalar> wrapu { repeat-definition }
<Scalar> wrapv { repeat-definition }
<Scalar> wrapw { repeat-definition }
This defines the behavior of the texture image outside of the
normal (u,v) range 0.0 - 1.0. It is "REPEAT" to repeat the
texture to infinity, "CLAMP" not to. The wrapping behavior may be
specified independently for each axis via "wrapu" and "wrapv", or
it may be specified for both simultaneously via "wrap".
Although less often used, for 3-d textures wrapw may also be
specified, and it behaves similarly to wrapu and wrapv.
There are other legal values in addtional to REPEAT and CLAMP.
The full list is:
CLAMP
REPEAT
MIRROR
MIRROR_ONCE
BORDER_COLOR
<Scalar> borderr { red-value }
<Scalar> borderg { green-value }
<Scalar> borderb { blue-value }
<Scalar> bordera { alpha-value }
These define the "border color" of the texture, which is
particularly important when one of the wrap modes, above, is
BORDER_COLOR.
<Scalar> type { texture-type }
This may be one of the following attributes:
1D
2D
3D
CUBE_MAP
The default is "2D", which specifies a normal, 2-d texture. If
any of the other types is specified instead, a texture image of
the corresponding type is loaded.
If 3D or CUBE_MAP is specified, then a series of texture images
must be loaded to make up the complete texture; in this case, the
texture filename is expected to include a sequence of one or more
hash mark ("#") characters, which will be filled in with the
sequence number. The first image in the sequence must be numbered
0, and there must be no gaps in the sequence. In this case, a
separate alpha-file designation is ignored; the alpha channel, if
present, must be included in the same image with the color
channel(s).
<Scalar> read-mipmaps { flag }
If this flag is nonzero, then pre-generated mipmap levels will be
loaded along with the texture. In this case, the filename should
contain a sequence of one or more hash mark ("#") characters,
which will be filled in with the mipmap level number; the texture
filename thus determines a series of images, one for each mipmap
level. The base texture image is mipmap level 0.
If this flag is specified in conjunction with a 3D or cube map
texture (as specified above), then the filename should contain two
hash mark sequences, separated by a character such as an
underscore, hyphen, or dot. The first sequence will be filled in
with the mipmap level index, and the second sequence will be
filled in with the 3D sequence or cube map face.
<Scalar> minfilter { filter-type }
<Scalar> magfilter { filter-type }
<Scalar> magfilteralpha { filter-type }
<Scalar> magfiltercolor { filter-type }
This specifies the type of filter applied when minimizing or
maximizing. Filter-type may be one of:
NEAREST
LINEAR
NEAREST_MIPMAP_NEAREST
LINEAR_MIPMAP_NEAREST
NEAREST_MIPMAP_LINEAR
LINEAR_MIPMAP_LINEAR
There are also some additional filter types that are supported for
historical reasons, but each of those additional types maps to one
of the above. New egg files should use only the above filter
types.
<Scalar> envtype { environment-type }
This specifies the type of texture environment to create; i.e. it
controls the way in which textures apply to models.
Environment-type may be one of:
MODULATE
DECAL
BLEND
REPLACE
ADD
BLEND_COLOR_SCALE
MODULATE_GLOW
MODULATE_GLOSS
*NORMAL
*NORMAL_HEIGHT
*GLOW
*GLOSS
*HEIGHT
*SELECTOR
The default environment type is MODULATE, which means the texture
color is multiplied with the base polygon (or vertex) color. This
is the most common texture environment by far. Other environment
types are more esoteric and are especially useful in the presence
of multitexture. In particular, the types prefixed by an asterisk
(*) require enabling Panda's automatic ShaderGenerator.
<Scalar> combine-rgb { combine-mode }
<Scalar> combine-alpha { combine-mode }
<Scalar> combine-rgb-source0 { combine-source }
<Scalar> combine-rgb-operand0 { combine-operand }
<Scalar> combine-rgb-source1 { combine-source }
<Scalar> combine-rgb-operand1 { combine-operand }
<Scalar> combine-rgb-source2 { combine-source }
<Scalar> combine-rgb-operand2 { combine-operand }
<Scalar> combine-alpha-source0 { combine-source }
<Scalar> combine-alpha-operand0 { combine-operand }
<Scalar> combine-alpha-source1 { combine-source }
<Scalar> combine-alpha-operand1 { combine-operand }
<Scalar> combine-alpha-source2 { combine-source }
<Scalar> combine-alpha-operand2 { combine-operand }
These options replace the envtype and specify the texture combiner
mode, which is usually used for multitexturing. This specifies
how the texture combines with the base color and/or the other
textures applied previously. You must specify both an rgb and an
alpha combine mode. Some combine-modes use one source/operand
pair, and some use all three; most use just two.
combine-mode may be one of:
REPLACE
MODULATE
ADD
ADD-SIGNED
INTERPOLATE
SUBTRACT
DOT3-RGB
DOT3-RGBA
combine-source may be one of:
TEXTURE
CONSTANT
PRIMARY-COLOR
PREVIOUS
CONSTANT_COLOR_SCALE
LAST_SAVED_RESULT
combine-operand may be one of:
SRC-COLOR
ONE-MINUS-SRC-COLOR
SRC-ALPHA
ONE-MINUS-SRC-ALPHA
The default values if any of these are omitted are:
<Scalar> combine-rgb { modulate }
<Scalar> combine-alpha { modulate }
<Scalar> combine-rgb-source0 { previous }
<Scalar> combine-rgb-operand0 { src-color }
<Scalar> combine-rgb-source1 { texture }
<Scalar> combine-rgb-operand1 { src-color }
<Scalar> combine-rgb-source2 { constant }
<Scalar> combine-rgb-operand2 { src-alpha }
<Scalar> combine-alpha-source0 { previous }
<Scalar> combine-alpha-operand0 { src-alpha }
<Scalar> combine-alpha-source1 { texture }
<Scalar> combine-alpha-operand1 { src-alpha }
<Scalar> combine-alpha-source2 { constant }
<Scalar> combine-alpha-operand2 { src-alpha }
<Scalar> saved-result { flag }
If flag is nonzero, then it indicates that this particular texture
stage will be supplied as the "last_saved_result" source for any
future texture stages.
<Scalar> tex-gen { mode }
This specifies that texture coordinates for the primitives that
reference this texture should be dynamically computed at runtime,
for instance to apply a reflection map or some other effect. The
valid values for mode are:
EYE_SPHERE_MAP (or SPHERE_MAP)
WORLD_CUBE_MAP
EYE_CUBE_MAP (or CUBE_MAP)
WORLD_NORMAL
EYE_NORMAL
WORLD_POSITION
EYE_POSITION
POINT_SPRITE
<Scalar> stage-name { name }
Specifies the name of the TextureStage object that is created to
render this texture. If this is omitted, a custom TextureStage is
created for this texture if it is required (e.g. because some
other multitexturing parameter has been specified), or the system
default TextureStage is used if multitexturing is not required.
<Scalar> priority { priority-value }
Specifies an integer sort value to rank this texture in priority
among other textures that are applied to the same geometry. This
is only used to eliminate low-priority textures in case more
textures are requested for a particular piece of geometry than the
graphics hardware can render.
<Scalar> blendr { red-value }
<Scalar> blendg { green-value }
<Scalar> blendb { blue-value }
<Scalar> blenda { alpha-value }
Specifies a four-component color that is applied with the color in
case the envtype, above, is "blend", or one of the combine-sources
is "constant".
<Scalar> uv-name { name }
Specifies the name of the texture coordinates that are to be
associated with this texture. If this is omitted, the default
texture coordinates are used.
<Scalar> rgb-scale { scale }
<Scalar> alpha-scale { scale }
Specifies an additional scale factor that will scale the r, g, b
(or a) components after the texture has been applied. This is
only used when a combine mode is in effect. The only legal values
are 1, 2, or 4.
<Scalar> alpha { alpha-type }
This specifies whether and what type of transparency will be
performed. Alpha-type may be one of:
OFF
ON
BLEND
BLEND_NO_OCCLUDE
MS
MS_MASK
If alpha-type is OFF, it means not to enable transparency, even if
the image contains an alpha channel or the format is RGBA. If
alpha-type is ON, it means to enable the default transparency,
even if the image filename does not contain an alpha channel. If
alpha-type is any of the other options, it specifies the type of
transparency to be enabled.
<Scalar> bin { bin-name }
This specifies the bin name order of all polygons with this
texture applied, in the absence of a bin name specified on the
polygon itself. See the description for bin under polygon
attributes.
<Scalar> draw_order { number }
This specifies the fixed drawing order of all polygons with this
texture applied, in the absence of a drawing order specified on
the polygon itself. See the description for draw_order under
polygon attributes.
<Scalar> quality-level { quality }
Sets a hint to the renderer about the desired performance /
quality tradeoff for this particular texture. This is most useful
for the tinydisplay software renderer; for normal,
hardware-accelerated renderers, this may have little or no effect.
This may be one of:
DEFAULT
FASTEST
NORMAL
BEST
"Default" means to use whatever quality level is specified by the
global texture-quality-level config variable.
<Transform> { transform-definition }
This specifies a 2-d or 3-d transformation that is applied to the
UV's of a surface to generate the texture coordinates.
The transform syntax is similar to that for groups, except it may
define either a 2-d 3x3 matrix or a 3-d 4x4 matrix. (You should
use the two-dimensional forms if the UV's are two-dimensional, and
the three-dimensional forms if the UV's are three-dimensional.)
A two-dimensional transform may be any sequence of zero or more of
the following. Transformations are post multiplied in the order
they are encountered to produce a net transformation matrix.
Rotations are counterclockwise about the origin in degrees.
Matrices, when specified explicitly, are row-major.
<Translate> { x y }
<Rotate> { degrees }
<Scale> { x y }
<Scale> { s }
<Matrix3> {
00 01 02
10 11 12
20 21 22
}
A three-dimensional transform may be any sequence of zero or more
of the following. See the description under <Group>, below, for
more information.
<Translate> { x y z }
<RotX> { degrees }
<RotY> { degrees }
<RotZ> { degrees }
<Rotate> { degrees x y z }
<Scale> { x y z }
<Scale> { s }
<Matrix4> {
00 01 02 03
10 11 12 13
20 21 22 23
30 31 32 33
}
<Material> name { [scalars] }
This defines a set of material attributes that may later be
referenced with <MRef> { name }.
The following attributes may appear within the material block:
<Scalar> diffr { number }
<Scalar> diffg { number }
<Scalar> diffb { number }
<Scalar> diffa { number }
<Scalar> ambr { number }
<Scalar> ambg { number }
<Scalar> ambb { number }
<Scalar> amba { number }
<Scalar> emitr { number }
<Scalar> emitg { number }
<Scalar> emitb { number }
<Scalar> emita { number }
<Scalar> specr { number }
<Scalar> specg { number }
<Scalar> specb { number }
<Scalar> speca { number }
<Scalar> shininess { number }
<Scalar> local { flag }
These properties collectively define a "material" that controls the
lighting effects that are applied to a surface; a material is only
in effect in the presence of lighting.
The four color groups, diff*, amb*, emit*, and spec* specify the
diffuse, ambient, emission, and specular components of the lighting
equation, respectively. Any of them may be omitted; the omitted
component(s) take their color from the native color of the
primitive, otherwise the primitive color is replaced with the
material color.
The shininess property controls the size of the specular highlight,
and the value ranges from 0 to 128. A larger value creates a
smaller highlight (creating the appearance of a shinier surface).
<VertexPool> name { vertices }
A vertex pool is a set of vertices. All geometry is created by
referring to vertices by number in a particular vertex pool. There
may be one or several vertex pools in an egg file, but all vertices
that make up a single polygon must come from the same vertex pool.
The body of a <VertexPool> entry is simply a list of one or more
<Vertex> entries, as follows:
<Vertex> number { x [y [z [w]]] [attributes] }
A <Vertex> entry is only valid within a vertex pool definition.
The number is the index by which this vertex will be referenced.
It is optional; if it is omitted, the vertices are implicitly
numbered consecutively beginning at one. If the number is
supplied, the vertices need not be consecutive.
Normally, vertices are three-dimensional (with coordinates x, y,
and z); however, in certain cases vertices may have fewer or more
dimensions, up to four. This is particularly true of vertices
used as control vertices of NURBS curves and surfaces. If more
coordinates are supplied than needed, the extra coordinates are
ignored; if fewer are supplied than needed, the missing
coordinates are assumed to be 0.
The vertex's coordinates are always given in world space,
regardless of any transforms before the vertex pool or before the
referencing geometry. If the vertex is referenced by geometry
under a transform, the egg loader will do an inverse transform to
move the vertex into the proper coordinate space without changing
its position in world space. One exception is geometry under an
<Instance> node; in this case the vertex coordinates are given in
the space of the <Instance> node. (Another exception is a
<DynamicVertexPool>; see below.)
In neither case does it make a difference whether the vertex pool
is itself declared under a transform or an <Instance> node. The
only deciding factor is whether the geometry that *uses* the
vertex pool appears under an <Instance> node. It is possible for
a single vertex to be interpreted in different coordinate spaces
by different polygons.
While each vertex must at least have a position, it may also have
a color, normal, pair of UV coordinates, and/or a set of morph
offsets. Furthermore, the color, normal, and UV coordinates may
themselves have morph offsets. Thus, the [attributes] in the
syntax line above may be replaced with zero or more of the
following entries:
<Dxyz> target { x y z }
This specifies the offset of this vertex for the named morph
target. See the "MORPH DESCRIPTION ENTRIES" header, below.
<Normal> { x y z [morph-list] }
This specifies the surface normal of the vertex. If omitted, the
vertex will have no normal. Normals may also be morphed;
morph-list here is thus an optional list of <DNormal> entries,
similar to the above.
<RGBA> { r g b a [morph-list] }
This specifies the four-valued color of the vertex. Each
component is in the range 0.0 to 1.0. A vertex color, if
specified for all vertices of the polygon, overrides the polygon's
color. If neither color is given, the default is white
(1 1 1 1). The morph-list is an optional list of <DRGBA> entries.
<UV> [name] { u v [w] [tangent] [binormal] [morph-list] }
This gives the texture coordinates of the vertex. This must be
specified if a texture is to be mapped onto this geometry.
The texture coordinates are usually two-dimensional, with two
component values (u v), but they may also be three-dimensional,
with three component values (u v w). (Arguably, it should be
called <UVW> instead of <UV> in the three-dimensional case, but
it's not.)
As before, morph-list is an optional list of <DUV> entries.
Unlike the other kinds of attributes, there may be multiple sets
of UV's on each vertex, each with a unique name; this provides
support for multitexturing. The name may be omitted to specify
the default UV's.
The UV's also support an optional tangent and binormal. These
values are based on the vertex normal and the UV coordinates of
connected vertices, and are used to render normal maps and similar
lighting effects. They are defined within the <UV> entry because
there may be a different set of tangents and binormals for each
different UV coordinate set. If present, they have the expected
syntax:
<UV> [name] { u v [w] <Tangent> { x y z } <Binormal> { x y z } }
<DynamicVertexPool> name { vertices }
A dynamic vertex pool is similar to a vertex pool in most respects,
except that each vertex might be animated by substituting in values
from a <VertexAnim> table. Also, the vertices defined within a
dynamic vertex pool are always given in local coordinates, instead
of world coordinates.
The presence of a dynamic vertex pool makes sense only within a
character model, and a single dynamic vertex pool may not span
multiple characters. Each dynamic vertex pool creates a DynVerts
object within the character by the same name; this name is used
later when matching up the corresponding <VertexAnim>.
At the present time, the DynamicVertexPool is not implemented in
Panda3D.
GEOMETRY ENTRIES
<Polygon> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
}
A polygon consists of a sequence of vertices from a single vertex
pool. Vertices are identified by pool-name and index number within
the pool; indices is a list of vertex numbers within the given
vertex pool. Vertices are listed in counterclockwise order.
Although the vertices must all come from the same vertex pool, they
may have been assigned to arbitrarily many different joints
regardless of joint connectivity (there is no "straddle-polygon"
limitation). See Joints, below.
The polygon syntax is quite verbose, and there isn't any way to
specify a set of attributes that applies to a group of polygons--the
attributes list must be repeated for each polygon. This is why egg
files tend to be very large.
The following attributes may be specified for polygons:
<TRef> { texture-name }
This refers to a named <Texture> entry given earlier. It applies
the given texture to the polygon. This requires that all the
polygon's vertices have been assigned texture coordinates.
This attribute may be repeated multiple times to specify
multitexture. In this case, each named texture is applied to the
polygon, in the order specified.
<Texture> { filename }
This is another way to apply a texture to a polygon. The
<Texture> entry is defined "inline" to the polygon, instead of
referring to a <Texture> entry given earlier. There is no way to
specify texture attributes given this form.
There's no advantage to this syntax for texture mapping. It's
supported only because it's required by some older egg files.
<MRef> { material-name }
This applies the material properties defined in the earlier
<Material> entry to the polygon.
<Normal> { x y z [morph-list] }
This defines a polygon surface normal. The polygon normal will be
used unless all vertices also have a normal. If no normal is
defined, none will be supplied. The polygon normal, like the
vertex normal, may be morphed by specifying a series of <DNormal>
entries.
The polygon normal is used only for lighting and environment
mapping calculations, and is not related to the implicit normal
calculated for CollisionPolygons.
<RGBA> { r g b a [morph-list] }
This defines the polygon's color, which will be used unless all
vertices also have a color. If no color is defined, the default
is white (1 1 1 1). The color may be morphed with a series of
<DRGBA> entries.
<BFace> { boolean-value }
This defines whether the polygon will be rendered double-sided
(i.e. its back face will be visible). By default, this option is
disabled, and polygons are one-sided; specifying a nonzero value
disables backface culling for this particular polygon and allows
it to be viewed from either side.
<Scalar> bin { bin-name }
It is sometimes important to control the order in which objects
are rendered, particularly when transparency is in use. In Panda,
this is achieved via the use of named bins and, within certain
kinds of bins, sometimes an explicit draw_order is also used (see
below).
In the normal (state-sorting) mode, Panda renders its geometry by
first grouping into one or more named bins, and then rendering the
bins in a specified order. The programmer is free to define any
number of bins, named whatever he/she desires.
This scalar specifies which bin this particular polygon is to be
rendered within. If no bin scalar is given, or if the name given
does not match any of the known bins, the polygon will be assigned
to the default bin, which renders all opaque geometry sorted by
state, followed by all transparent geometry sorted back-to-front.
See also draw_order, below.
<Scalar> draw_order { number }
This works in conjunction with bin, above, to further refine the
order in which this polygon is drawn, relative to other geometry
in the same bin. If (and only if) the bin type named in the bin
scalar is a CullBinFixed, this draw_order is used to define the
fixed order that all geometry in the same will be rendered, from
smaller numbers to larger numbers.
If the draw_order scalar is specified but no bin scalar is
specified, the default is a bin named "fixed", which is a
CullBinFixed object that always exists by default.
<Scalar> visibility { hidden | normal }
If the visibility of a primitive is set to "hidden", the primitive
is not generated as a normally visible primitive. If the
Config.prc variable egg-suppress-hidden is set to true, the
primitive is not converted at all; otherwise, it is converted as a
"stashed" node.
This, like the other rendering flags alpha, draw_order, and bin,
may be specified at the group level, within the primitive level,
or even within a texture.
<PointLight> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
}
A PointLight is a set of single points. One point is drawn for each
vertex listed in the <VertexRef>. Normals, textures, and colors may
be specified for PointLights, as well as draw_order, plus one
additional attribute valid only for PointLights and Lines:
<Scalar> thick { number }
This specifies the size of the PointLight (or the width of a
line), in pixels, when it is rendered. This may be a
floating-point number, but the fractional part is meaningful only
when antialiasing is in effect. The default is 1.0.
<Scalar> perspective { boolean-value }
If this is specified, then the thickness, above, is to interpreted
as a size in 3-d spatial units, rather than a size in pixels, and
the point should be scaled according to its distance from the
viewer normally.
<Line> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
[component attributes]
}
A Line is a connected set of line segments. The listed N vertices
define a series of N-1 line segments, drawn between vertex 0 and
vertex 1, vertex 1 and vertex 2, etc. The line is not implicitly
closed; if you wish to represent a loop, you must repeat vertex 0 at
the end. As with a PointLight, normals, textures, colors,
draw_order, and the "thick" attribute are all valid (but not
"perspective"). Also, since a Line (with more than two vertices) is
made up of multiple line segments, it may contain a number of
<Component> entries, to set a different color and/or normal for each
line segment, as in TriangleStrip, below.
<TriangleStrip> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
[component attributes]
}
A triangle strip is only rarely encountered in an egg file; it is
normally generated automatically only during load time, when
connected triangles are automatically meshed for loading, and even
then it exists only momentarily. Since a triangle strip is a
rendering optimization only and adds no useful scene information
over a loose collection of triangles, its usage is contrary to the
general egg philosophy of representing a scene in the abstract.
Nevertheless, the syntax exists, primarily to allow inspection of
the meshing results when needed. You can also add custom
TriangleStrip entries to force a particular mesh arrangement.
A triangle strip is defined as a series of connected triangles.
After the first three vertices, which define the first triangle,
each new vertex defines one additional triangle, by alternating up
and down.
It is possible for the individual triangles of a triangle strip to
have a separate normal and/or color. If so, a <Component> entry
should be given for each so-modified triangle:
<Component> index {
<RGBA> { r g b a [morph-list] }
<Normal> { x y z [morph-list] }
}
Where index ranges from 0 to the number of components defined by the
triangle strip (less 1). Note that the component attribute list
must always follow the vertex list.
<TriangleFan> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
[component attributes]
}
A triangle fan is similar to a triangle strip, except all of the
connected triangles share the same vertex, which is the first
vertex. See <TriangleStrip>, above.
PARAMETRIC DESCRIPTION ENTRIES
The following entries define parametric curves and surfaces.
Generally, Panda supports these only in the abstract; they're not
geometry in the true sense but do exist in the scene graph and may
have specific meaning to the application. However, Panda can create
visible representations of these parametrics to aid visualization.
These entries might also have meaning to external tools outside of an
interactive Panda session, such as egg-qtess, which can be used to
convert NURBS surfaces to polygons at different levels of resolution.
In general, dynamic attributes such as morphs and joint assignment are
legal for the control vertices of the following parametrics, but Panda
itself doesn't support them and will always create static curves and
surfaces. External tools like egg-qtess, however, may respect them.
<NURBSCurve> {
[attributes]
<Order> { order }
<Knots> { knot-list }
<VertexRef> { indices <Ref> { pool-name } }
}
A NURBS curve is a general parametric curve. It is often used to
represent a motion path, e.g. for a camera or an object.
The order is equal to the degree of the polynomial basis plus 1. It
must be an integer in the range [1,4].
The number of vertices must be equal to the number of knots minus the
order.
Each control vertex of a NURBS is defined in homogeneous space with
four coordinates x y z w (to convert to 3-space, divide x, y, and z
by w). The last coordinate is always the homogeneous coordinate; if
only three coordinates are given, it specifies a curve in two
dimensions plus a homogeneous coordinate (x y w).
The following attributes may be defined:
<Scalar> type { curve-type }
This defines the semanting meaning of this curve, either XYZ, HPR,
or T. If the type is XYZ, the curve will automatically be
transformed between Y-up and Z-up if necessary; otherwise, it will
be left alone.
<Scalar> subdiv { num-segments }
If this scalar is given and nonzero, Panda will create a visible
representation of the curve when the scene is loaded. The number
represents the number of line segments to draw to approximate the
curve.
<RGBA> { r g b a [morph-list] }
This specifies the color of the overall curve.
NURBS control vertices may also be given color and/or morph
attributes, but <Normal> and <UV> entries do not apply to NURBS
vertices.
<NURBSSurface> name {
[attributes]
<Order> { u-order v-order }
<U-knots> { u-knot-list }
<V-knots> { v-knot-list }
<VertexRef> {
indices
<Ref> { pool-name }
}
}
A NURBS surface is an extension of a NURBS curve into two parametric
dimensions, u and v. NURBS surfaces may be given the same set of
attributes assigned to polygons, except for normals: <TRef>,
<Texture>, <MRef>, <RGBA>, and draw_order are all valid attributes
for NURBS. NURBS vertices, similarly, may be colored or morphed,
but <Normal> and <UV> entries do not apply to NURBS vertices. The
attributes may also include <NURBSCurve> and <Trim> entries; see
below.
To have Panda create a visualization of a NURBS surface, the
following two attributes should be defined as well:
<Scalar> U-subdiv { u-num-segments }
<Scalar> V-subdiv { v-num-segments }
These define the number of subdivisions to make in the U and V
directions to represent the surface. A uniform subdivision is
always made, and trim curves are not respected (though they will
be drawn in if the trim curves themselves also have a subiv
parameter). This is only intended as a cheesy visualization.
The same sort of restrictions on order and knots applies to NURBS
surfaces as do to NURBS curves. The order and knot description may
be different in each dimension.
The surface must have u-num * v-num vertices, where u-num is the
number of u-knots minus the u-order, and v-num is the number of
v-knots minus the v-order. All vertices must come from the same
vertex pool. The nth (zero-based) index number defines control
vertex (u, v) of the surface, where n = (v * u-num) + u. Thus, it
is the u coordinate which changes faster.
As with the NURBS curve, each control vertex is defined in
homogeneous space with four coordinates x y z w.
A NURBS may also contain curves on its surface. These are one or
more nested <NURBSCurve> entries included with the attributes; these
curves are defined in the two-dimensional parametric space of the
surface. Thus, these curve vertices should have only two dimensions
plus the homogeneous coordinate: u v w. A curve-on-surface has no
intrinsic meaning to the surface, unless it is defined within a
<Trim> entry, below.
Finally, a NURBS may be trimmed by one or more trim curves. These
are special curves on the surface which exclude certain areas from
the NURBS surface definition. The inside is specified using two
rules: an odd winding rule that states that the inside consists of
all regions for which an infinite ray from any point in the region
will intersect the trim curve an odd number of times, and a curve
orientation rule that states that the inside consists of the regions
to the left as the curve is traced.
Each trim curve contains one or more loops, and each loop contains
one or more NURBS curves. The curves of a loop connect in a
head-to-tail fashion and must be explicitly closed.
The trim curve syntax is as follows:
<Trim> {
<Loop> {
<NURBSCurve> {
<Order> { order }
<Knots> { knot-list }
<VertexRef> { indices <Ref> { pool-name } }
}
[ <NURBSCurve> { ... } ... ]
}
[ <Loop> { ... } ... ]
}
Although the egg syntax supports trim curves, there are at present
no egg processing tools that respect them. For instance, egg-qtess
ignores trim curves and always tesselates the entire NURBS surface.
MORPH DESCRIPTION ENTRIES
Morphs are linear interpolations of attribute values at run time,
according to values read from an animation table. In general, vertex
positions, surface normals, texture coordinates, and colors may be
morphed.
A morph target is defined by giving a net morph offset for a series of
vertex or polygon attributes; this offset is the value that will be
added to the attribute when the morph target has the value 1.0. At
run time, the morph target's value may be animated to any scalar value
(but generally between 0.0 and 1.0); the corresponding fraction of the
offset is added to the attribute each frame.
There is no explicit morph target definition; a morph target exists
solely as the set of all offsets that share the same target name. The
target name may be any arbitrary string; like any name in an egg file,
it should be quoted if it contains special characters.
The following types of morph offsets may be defined, within their
corresponding attribute entries:
<Dxyz> target { x y z }
A position delta, valid within a <Vertex> entry or a <CV> entry.
The given offset vector, scaled by the morph target's value, is
added to the vertex or CV position each frame.
<DNormal> target { x y z }
A normal delta, similar to the position delta, valid within a
<Normal> entry (for vertex or polygon normals). The given offset
vector, scaled by the morph target's value, is added to the normal
vector each frame. The resulting vector may not be automatically
normalized to unit length.
<DUV> target { u v [w] }
A texture-coordinate delta, valid within a <UV> entry (within a
<Vertex> entry). The offset vector should be 2-valued if the
enclosing UV is 2-valued, or 3-valued if the enclosing UV is
3-valued. The given offset vector, scaled by the morph target's
value, is added to the vertex's texture coordinates each frame.
<DRGBA> target { r g b a }
A color delta, valid within an <RGBA> entry (for vertex or polygon
colors). The given 4-valued offset vector, scaled by the morph
target's value, is added to the color value each frame.
GROUPING ENTRIES
<Group> name { group-body }
A <Group> node is the primary means of providing structure to the
egg file. Groups can contain vertex pools and polygons, as well as
other groups. The egg loader translates <Group> nodes directly into
PandaNodes in the scene graph (although the egg loader reserves the
right to arbitrarily remove nodes that it deems unimportant--see the
<Model> flag, below to avoid this). In addition, the following
entries can be given specifically within a <Group> node to specify
attributes of the group:
GROUP BINARY ATTRIBUTES
These attributes may be either on or off; they are off by default.
They are turned on by specifying a non-zero "boolean-value".
<DCS> { boolean-value }
DCS stands for Dynamic Coordinate System. This indicates that
show code will expect to be able to read the transform set on this
node at run time, and may need to modify the transform further.
This is a special case of <Model>, below.
<DCS> { dcs-type }
This is another syntax for the <DCS> flag. The dcs-type string
should be one of either "local" or "net", which specifies the kind
of preserve_transform flag that will be set on the corresponding
ModelNode. If the string is "local", it indicates that the local
transform on this node (as well as the net transform) will not be
affected by any flattening operation and will be preserved through
the entire model loading process. If the string is "net", then
only the net transform will be preserved; the local transform may
be adjusted in the event of a flatten operation.
<Model> { boolean-value }
This indicates that the show code might need a pointer to this
particular group. This creates a ModelNode at the corresponding
level, which is guaranteed not to be removed by any flatten
operation. However, its transform might still be changed, but see
also the <DCS> flag, above.
<Dart> { boolean-value }
This indicates that this group begins an animated character. A
Character node, which is the fundamental animatable object of
Panda's high-level Actor class, will be created for this group.
This flag should always be present within the <Group> entry at the
top of any hierarchy of <Joint>'s and/or geometry with morphed
vertices; joints and morphs appearing outside of a hierarchy
identified with a <Dart> flag are undefined.
<Switch> { boolean-value }
This attribute indicates that the child nodes of this group
represent a series of animation frames that should be
consecutively displayed. In the absence of an "fps" scalar for
the group (see below), the egg loader creates a SwitchNode, and it
the responsibility of the show code to perform the switching. If
an fps scalar is defined and is nonzero, the egg loader creates a
SequenceNode instead, which automatically cycles through its
children.
GROUP SCALARS
<Scalar> fps { frame-rate }
This specifies the rate of animation for a SequenceNode (created
when the Switch flag is specified, see above). A value of zero
indicates a SwitchNode should be created instead.
<Scalar> bin { bin-name }
This specifies the bin name for all polygons at or below this node
that do not explicitly set their own bin. See the description of
bin for geometry attributes, above.
<Scalar> draw_order { number }
This specifies the drawing order for all polygons at or below this
node that do not explicitly set their own drawing order. See the
description of draw_order for geometry attributes, above.
<Scalar> visibility { hidden | normal }
If the visibility of a group is set to "hidden", the primitives
nested within that group are not generated as a normally visible
primitive. If the Config.prc variable egg-suppress-hidden is set
to true, the primitives are not converted at all; otherwise, they
are converted as a "stashed" node.
<Scalar> decal { boolean-value }
If this is present and boolean-value is non-zero, it indicates
that the geometry *below* this level is coplanar with the geometry
*at* this level, and the geometry below is to be drawn as a decal
onto the geometry at this level. This means the geometry below
this level will be rendered "on top of" this geometry, but without
the Z-fighting artifacts one might expect without the use of the
decal flag.
<Scalar> decalbase { boolean-value }
This can optionally be used with the "decal" scalar, above. If
present, it should be applied to a sibling of one or more nodes
with the "decal" scalar on. It indicates which of the sibling
nodes should be treated as the base of the decal. In the absence
of this scalar, the parent of all decal nodes is used as the decal
base. This scalar is useful when the modeling package is unable
to parent geometry nodes to other geometry nodes.
<Scalar> collide-mask { value }
<Scalar> from-collide-mask { value }
<Scalar> into-collide-mask { value }
Sets the CollideMasks on the collision nodes and geometry nodes
created at or below this group to the indicated values. These
are bits that indicate which objects can collide with which
other objects. Setting "collide-mask" is equivalent to setting
both "from-collide-mask" and "into-collide-mask" to the same
value.
The value may be an ordinary decimal integer, or a hex number in
the form 0x000, or a binary number in the form 0b000.
<Scalar> blend { mode }
Specifies that a special blend mode should be applied geometry at
this level and below. The available options are none, add,
subtract, inv-subtract, min, and max. See ColorBlendAttrib.
<Scalar> blendop-a { mode }
<Scalar> blendop-b { mode }
If blend mode, above, is not none, this specifies the A and B
operands to the blend equation. Common options are zero, one,
incoming-color, one-minus-incoming-color. See ColorBlendAttrib
for the complete list of available options. The default is "one".
<Scalar> blendr { red-value }
<Scalar> blendg { green-value }
<Scalar> blendb { blue-value }
<Scalar> blenda { alpha-value }
If blend mode, above, is not none, and one of the blend operands
is constant-color or a related option, this defines the constant
color that will be used.
OTHER GROUP ATTRIBUTES
<Billboard> { type }
This entry indicates that all geometry defined at or below this
group level is part of a billboard that will rotate to face the
camera. Type is either "axis" or "point", describing the type of
rotation.
Billboards rotate about their local axis. In the case of a Y-up
file, the billboards rotate about the Y axis; in a Z-up file, they
rotate about the Z axis. Point-rotation billboards rotate about
the origin.
There is an implicit <Instance> around billboard geometry. This
means that the geometry within a billboard is not specified in
world coordinates, but in the local billboard space. Thus, a
vertex drawn at point 0,0,0 will appear to be at the pivot point
of the billboard, not at the origin of the scene.
<SwitchCondition> {
<Distance> {
in out [fade] <Vertex> { x y z }
}
}
The subtree beginning at this node and below represents a single
level of detail for a particular model. Sibling nodes represent
the additional levels of detail. The geometry at this node will
be visible when the point (x, y, z) is closer than "in" units, but
further than "out" units, from the camera. "fade" is presently
ignored.
<Tag> key { value }
This attribute defines the indicated tag (as a key/value pair),
retrievable via NodePath::get_tag() and related interfaces, on
this node.
<Collide> name { type [flags] }
This entry indicates that geometry defined at this group level is
actually an invisible collision surface, and is not true geometry.
The geometry is used to define the extents of the collision
surface. If there is no geometry defined at this level, then a
child is searched for with the same collision type specified, and
its geometry is used to define the extent of the collision
surface (unless the "descend" flag is given; see below).
Valid types so far are:
Plane
The geometry represents an infinite plane. The first polygon
found in the group will define the plane.
Polygon
The geometry represents a single polygon. The first polygon is
used.
Polyset
The geometry represents a complex shape made up of several
polygons. This collision type should not be overused, as it
provides the least optimization benefit.
Sphere
The geometry represents a sphere. The vertices in the group are
averaged together to determine the sphere's center and radius.
InvSphere
The geometry represents an inverse sphere. This is the same as
Sphere, with the normal inverted, so that the solid part of an
inverse sphere is the entire world outside of it. Note that an
inverse sphere is in infinitely large solid with a finite hole
cut into it.
Tube
The geometry represents a tube. This is a cylinder-like shape
with hemispherical endcaps; it is sometimes called a capsule or
a lozenge in other packages. The smallest tube shape that will
fit around the vertices is used.
The flags may be any zero or more of:
event
Throws the name of the <Collide> entry, or the name of the
surface if the <Collide> entry has no name, as an event whenever
an avatar strikes the solid. This is the default if the
<Collide> entry has a name.
intangible
Rather than being a solid collision surface, the defined surface
represents a boundary. The name of the surface will be thrown
as an event when an avatar crosses into the interior, and
name-out will be thrown when an avater exits.
descend
Instead of creating only one collision object of the given type,
each group descended from this node that contains geometry will
define a new collision object of the given type. The event
name, if any, will also be inherited from the top node and
shared among all the collision objects.
keep
Don't discard the visible geometry after using it to define a
collision surface; create both an invisible collision surface
and the visible geometry.
level
Stores a special effective normal with the collision solid that
points up, regardless of the actual shape or orientation of the
solid. This can be used to allow an avatar to stand on a
sloping surface without having a tendency to slide downward.
<ObjectType> { type }
This is a short form to indicate one of several pre-canned sets of
attributes. Type may be any word, and a Config definition will be
searched for by the name "egg-object-type-word", where "word" is
the type word. This definition may contain any arbitrary egg
syntax to be parsed in at this group level.
A number of predefined ObjectType definitions are provided:
barrier
This is equivalent to <Collide> { Polyset descend }. The
geometry defined at this root and below defines an invisible
collision solid.
trigger
This is equivalent to <Collide> { Polyset descend intangible }.
The geometry defined at this root and below defines an invisible
trigger surface.
sphere
Equivalent to <Collide> { Sphere descend }. The geometry is
replaced with the smallest collision sphere that will enclose
it. Typically you model a sphere in polygons and put this flag
on it to create a collision sphere of the same size.
tube
Equivalent to <Collide> { Tube descend }. As in sphere, above,
but the geometry is replaced with a collision tube (a capsule).
Typically you will model a capsule or a cylinder in polygons.
bubble
Equivalent to <Collide> { Sphere keep descend }. A collision
bubble is placed around the geometry, which is otherwise
unchanged.
ghost
Equivalent to <Scalar> collide-mask { 0 }. It means that the
geometry beginning at this node and below should never be
collided with--characters will pass through it.
backstage
This has no equivalent; it is treated as a special case. It
means that the geometry at this node and below should not be
translated. This will normally be used on scale references and
other modeling tools.
There may also be additional predefined egg object types not
listed here; see the *.pp files that are installed into the etc
directory for a complete list.
<Transform> { transform-definition }
This specifies a matrix transform at this group level. This
defines a local coordinate space for this group and its
descendents. Vertices are still specified in world coordinates
(in a vertex pool), but any geometry assigned to this group will
be inverse transformed to move its vertices to the local space.
The transform definition may be any sequence of zero or more of
the following. Transformations are post multiplied in the order
they are encountered to produce a net transformation matrix.
Rotations are defined as a counterclockwise angle in degrees about
a particular axis, either implicit (about the x, y, or z axis), or
arbitrary. Matrices, when specified explicitly, are row-major.
<Translate> { x y z }
<RotX> { degrees }
<RotY> { degrees }
<RotZ> { degrees }
<Rotate> { degrees x y z }
<Scale> { x y z }
<Scale> { s }
<Matrix4> {
00 01 02 03
10 11 12 13
20 21 22 23
30 31 32 33
}
Note that the <Transform> block should always define a 3-d
transform when it appears within the body of a <Group>, while it
may define either a 2-d or a 3-d transform when it appears within
the body of a <Texture>. See <Texture>, above.
<DefaultPose> { transform-definition }
This defines an optional default pose transform, which might be a
different transform from that defined by the <Transform> entry,
above. This makes sense only for a <Joint>. See the <Joint>
description, below.
The default pose transform defines the transform the joint will
maintain in the absence of any animation being applied. This is
different from the <Transform> entry, which defines the coordinate
space the joint must have in order to keep its vertices in their
(global space) position as given in the egg file. If this is
different from the <Transform> entry, the joint's vertices will
*not* be in their egg file position at initial load. If there is
no <DefaultPose> entry for a particular joint, the implicit
default-pose transform is the same as the <Transform> entry.
Normally, the <DefaultPose> entry, if any, is created by the
egg-optchar -defpose option. Most other software has little
reason to specify an explicit <DefaultPose>.
<VertexRef> { indices <Ref> { pool-name } }
This moves geometry created from the named vertices into the
current group, regardless of the group in which the geometry is
actually defined. See the <Joint> description, below.
<AnimPreload> {
<Scalar> fps { float-value }
<Scalar> num-frames { integer-value }
}
One or more AnimPreload entries may appear within the <Group> that
contains a <Dart> entry, indicating an animated character (see
above). These AnimPreload entries record the minimal preloaded
animation data required in order to support asynchronous animation
binding. These entries are typically generated by the egg-optchar
program with the -preload option, and are used by the Actor code
when allow-async-bind is True (the default).
<Instance> name { group-body }
An <Instance> node is exactly like a <Group> node, except that
vertices referenced by geometry created under the <Instance> node
are not assumed to be given in world coordinates, but are instead
given in the local space of the <Instance> node itself (including
any transforms given to the node).
In other words, geometry under an <Instance> node is defined in
local coordinates. In principle, similar geometry can be created
under several different <Instance> nodes, and thus can be positioned
in a different place in the scene each instance. This doesn't
necessarily imply the use of shared geometry in the Panda3D scene
graph, but see the <Ref> syntax, below.
This is particularly useful in conjunction with a <File> entry, to
load external file references at places other than the origin.
A special syntax of <Instance> entries does actually create shared
geometry in the scene graph. The syntax is:
<Instance> name {
<Ref> { group-name }
[ <Ref> { group-name } ... ]
}
In this case, the referenced group name will appear as a duplicate
instance in this part of the tree. Local transforms can be applied
and are relative to the referencing group's transform. The
referenced group must appear preceding this point in the egg file,
and it will also be a part of the scene in the point at which it
first appears. The referenced group may be either a <Group> or an
<Instance> of its own; usually, it is a <Group> nested within an
earlier <Instance> entry.
<Joint> name { [transform] [ref-list] [joint-list] }
A joint is a highly specialized kind of grouping node. A tree of
joints is used to specify the skeletal structure of an animated
character.
A joint may only contain one of three things. It may contain a
<Transform> entry, as above, which defines the joint's unanimated
(rest) position; it may contain lists of assigned vertices or CV's;
and it may contain other joints.
A tree of <Joint> nodes only makes sense within a character
definition, which is created by applying the <DART> flag to a group.
See <DART>, above.
The vertex assignment is crucial. This is how the geometry of a
character is made to move with the joints. The character's geometry
is actually defined outside the joint tree, and each vertex must be
assigned to one or more joints within the tree.
This is done with zero or more <VertexRef> entries per joint, as the
following:
<VertexRef> { indices [<Scalar> membership { m }] <Ref> { pool-name } }
This is syntactically similar to the way vertices are assigned to
polygons. Each <VertexRef> entry can assign vertices from only one
vertex pool (but there may be many <VertexRef> entries per joint).
Indices is a list of vertex numbers from the specied vertex pool, in
an arbitrary order.
The membership scalar is optional. If specified, it is a value
between 0.0 and 1.0 that indicates the fraction of dominance this
joint has over the vertices. This is used to implement
soft-skinning, so that each vertex may have partial ownership in
several joints.
The <VertexRef> entry may also be given to ordinary <Group> nodes.
In this case, it treats the geometry as if it was parented under the
group in the first place. Non-total membership assignments are
meaningless.
<Bundle> name { table-list }
<Table> name { table-body }
A table is a set of animated values for joints. A tree of tables
with the same structure as the corresponding tree of joints must be
defined for each character to be animated. Such a tree is placed
under a <Bundle> node, which provides a handle within Panda to the
tree as a whole.
Bundles may only contain tables; tables may contain more tables,
bundles, or any one of the following (<Scalar> entries are optional,
and default as shown):
<S$Anim> name {
<Scalar> fps { 24 }
<V> { values }
}
This is a table of scalar values, one per frame. This may be
applied to a morph slider, for instance.
<Xfm$Anim> name {
<Scalar> fps { 24 }
<Scalar> order { srpht }
<Scalar> contents { ijkabcrphxyz }
<V> { values }
}
This is a table of matrix transforms, one per frame, such as may
be applied to a joint. The "contents" string consists of a subset
of the letters "ijkabcrphxyz", where each letter corresponds to a
column of the table; <V> is a list of numbers of length(contents)
* num_frames. Each letter of the contents string corresponds to a
type of transformation:
i, j, k - scale in x, y, z directions, respectively
a, b, c - shear in xy, xz, and yz planes, respectively
r, p, h - rotate by pitch, heading, roll
x, y, z - translate in x, y, z directions
The net transformation matrix specified by each row of the table
is defined as the net effect of each of the individual columns'
transform, according to the corresponding letter in the contents
string. The order the transforms are applied is defined by the
order string:
s - all scale and shear transforms
r, p, h - individual rotate transforms
t - all translation transforms
<Xfm$Anim_S$> name {
<Scalar> fps { 24 }
<Scalar> order { srpht }
<S$Anim> i { ... }
<S$Anim> j { ... }
...
}
This is a variant on the <Xfm$Anim> entry, where each column of
the table is entered as a separate <S$Anim> table. This syntax
reflects an attempt to simplify the description by not requiring
repetition of values for columns that did not change value during
an animation sequence.
<VertexAnim> name {
<Scalar> width { table-width }
<Scalar> fps { 24 }
<V> { values }
}
This is a table of vertex positions, normals, texture coordinates,
or colors. These values will be subsituted at runtime for the
corresponding values in a <DynamicVertexPool>. The name of the
table should be "coords", "norms", "texCoords", or "colors",
according to the type of values defined. The number table-width
is the number of floats in each row of the table. In the case of
a coords or norms table, this must be 3 times the number of
vertices in the corresponding dynamic vertex pool. (For texCoords
and colors, this number must be 2 times and 4 times, respectively.)
MISCELLANEOUS
<File> { filename }
This includes a copy of the referenced egg file at the current
point. This is usually placed under an <Instance> node, so that the
current transform will apply to the geometry in the external file.
The extension ".egg" is implied if it is omitted.
As with texture filenames, the filename may be a relative path, in
which case the current egg file's directory is searched first, and
then the model-path is searched.
ANIMATION STRUCTURE
Unanimated models may be defined in egg files without much regard to
any particular structure, so long as named entries like VertexPools
and Textures appear before they are referenced.
However, a certain rigid structural convention must be followed in
order to properly define an animated skeleton-morph model and its
associated animation data.
The structure for an animated model should resemble the following:
<Group> CHARACTER_NAME {
<Dart> { 1 }
<Joint> JOINT_A {
<Transform> { ... }
<VertexRef> { ... }
<Group> { <Polygon> ... }
<Joint> JOINT_B {
<Transform> { ... }
<VertexRef> { ... }
<Group> { <Polygon> ... }
}
<Joint> JOINT_C {
<Transform> { ... }
<VertexRef> { ... }
<Group> { <Polygon> ... }
}
...
}
}
The <Dart> flag is necessary to indicate that this group begins an
animated model description. Without the <Dart> flag, joints will be
treated as ordinary groups, and morphs will be ignored.
In the above, UPPERCASE NAMES represent an arbitrary name that you
may choose. The name of the enclosing group, CHARACTER_NAME, is
taken as the name of the animated model. It should generally match
the bundle name in the associated animation tables.
Within the <Dart> group, you may define an arbitrary hierarchy of
<Joint> entries. There may be as many <Joint> entries as you like,
and they may have any nesting complexity you like. There may be
either one root <Joint>, or multiple roots. However, you must
always include at least one <Joint>, even if your animation consists
entirely of morphs.
Polygons may be directly attached to joints by enclosing them within
the <Joint> group, perhaps with additional nesting <Group> entries,
as illustrated above. This will result in the polygon's vertices
being hard-assigned to the joint it appears within. Alternatively,
you declare the polygons elsewhere in the egg file, and use
<VertexRef> entries within the <Joint> group to associate the
vertices with the joints. This is the more common approach, since
it allows for soft-assignment of vertices to multiple joints.
It is not necessary for every joint to have vertices at all. Every
joint should include a transform entry, however, which defines the
initial, resting transform of the joint (but see also <DefaultPose>,
above). If a transform is omitted, the identity transform is
assumed.
Some of the vertex definitions may include morph entries, as
described in MORPH DESCRIPTION ENTRIES, above. These are meaningful
only for vertices that are assigned, either implicitly or
explicitly, to at least one joint.
You may have multiple versions of a particular animated model--for
instance, multiple different LOD's, or multiple different clothing
options. Normally each different version is stored in a different
egg file, but it is also possible to include multiple versions
within the same egg file. If the different versions are intended to
play the same animations, they should all have the same
CHARACTER_NAME, and their joint hierarchies should exactly match in
structure and names.
The structure for an animation table should resemble the following:
<Table> {
<Bundle> CHARACTER_NAME {
<Table> "<skeleton>" {
<Table> JOINT_A {
<Xfm$Anim_S$> xform {
<Char*> order { sphrt }
<Scalar> fps { 24 }
<S$Anim> x { 0 0 10 10 20 ... }
<S$Anim> y { 0 0 0 0 0 ... }
<S$Anim> z { 20 20 20 20 20 ... }
}
<Table> JOINT_B {
<Xfm$Anim_S$> xform {
<Char*> order { sphrt }
<Scalar> fps { 24 }
<S$Anim> x { ... }
<S$Anim> y { ... }
<S$Anim> z { ... }
}
}
<Table> JOINT_C {
<Xfm$Anim_S$> xform {
<Char*> order { sphrt }
<Scalar> fps { 24 }
<S$Anim> x { ... }
<S$Anim> y { ... }
<S$Anim> z { ... }
}
}
}
}
<Table> morph {
<S$Anim> MORPH_A {
<Scalar> fps { 24 }
<V> { 0 0 0 0.1 0.2 0.3 1 ... }
}
<S$Anim> MORPH_B {
<Scalar> fps { 24 }
<V> { ... }
}
<S$Anim> MORPH_C {
<Scalar> fps { 24 }
<V> { ... }
}
}
}
}
The <Bundle> entry begins an animation table description. This
entry must have at least one child: a <Table> named "<skeleton>"
(this name is a literal keyword and must be present). The children
of this <Table> entry should be a hierarchy of additional <Table>
entries, one for each joint in the model. The joint structure and
names defined by the <Table> hierarchy should exactly match the
joint structure and names defined by the <Joint> hierarchy in the
corresponding model.
Each <Table> that corresponds to a joint should have one child, an
<Xfm$Anim_S$> entry named "xform" (this name is a literal keyword
and must be present). Within this entry, there is a series of up to
twelve <S$Anim> entries, each with a one-letter name like "x", "y",
or "z", which define the per-frame x, y, z position of the
corresponding joint. There is one numeric entry for each frame, and
all frames represent the same length of time. You can also define
rotation, scale, and shear. See the full description of
<Xfm$Anim_S$>, above.
Within a particular animation bundle, all of the various components
throughout the various <Tables> should define the same number of
frames, with the exception that if any of them define exactly one
frame value, that value is understood to be replicated the
appropriate number of times to match the number of frames defined by
other components.
(Note that you may alternatively define an animation table with an
<Xfm$Anim> entry, which defines all of the individual components in
one big matrix instead of individually. See the full description
above.)
Each joint defines its frame rate independently, with an "fps"
scalar. This determines the number of frames per second for the
frame data within this table. Typically, all joints have the same
frame rate, but it is possible for different joints to animate at
different speeds.
Each joint also defines the order in which its components should be
composed to determine the complete transform matrix, with an "order"
scalar. This is described in more detail above.
If any of the vertices in the model have morphs, the top-level
<Table> should also include a <Table> named "morph" (this name is
also a literal keyword). This table in turn contains a list of
<S$Anim> entries, one for each named morph description. Each table
contains a list of numeric values, one per frame; as with the joint
data, there should be the same number of numeric values in all
tables, with the exception that just one value is understood to mean
hold that value through the entire animation.
The "morph" table may be omitted if there are no morphs defined in
the model.
There should be a separate <Bundle> definition for each different
animation. The <Bundle> name should match the CHARACTER_NAME used
for the model, above. Typically each bundle is stored in a separate
egg file, but it is also possible to store multiple different
animation bundles within the same egg file. If you do this, you may
violate the CHARACTER_NAME rule, and give each bundle a different
name; this will become the name of the animation in the Actor
interface.
Although animations and models are typically stored in separate egg
files, it is possible to store them together in one large egg file.
The Actor interface will then make available all of the animations
it finds within the egg file, by bundle name.
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