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open_toontown_panda3d/panda/src/doc/eggSyntax.txt

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Egg files can, naturally, 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. Traditionally the scene descriptions,
character descriptions, and animation tables have been stored in three
different kinds of egg files (and, in the old player, parsed by
different egg loaders, which didn't even accept the same syntax); this
distinction is no longer as important. There is only one egg loader,
and a single egg file can contain elements of all three.
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 Egg
evolved, <Scalar> and <Char*> are lexically the same and both can
represent either a string or a number.
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 is a new kind of node introduced for the new player. The old
player used a Y-up coordinate system, so all modeling was done with
Y-up and egg files used Y-up implicitly. Since we have adopted a
Z-up coordinate system with the new player, it becomes necessary to
make a distinction. The contents of this entry are either the
string "Y-up" or "Z-up" to indicate the coordinate system used in
the egg file; the egg loader will automatically make a conversion if
necessary. By convention, this entry should only appear at the
beginning of the 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.
The filename may be a relative path, in which case it is relative to
the directory in which the current egg file was found. If no
directory prefix is specified, the current egg file's directory is
searched first, and then $PFPATH is searched.
The following attributes are presently implemented for textures:
<Scalar> format { format-definition }
This defines the load format of the image file. The
format-definition is one of:
RGBA, RGBA12, RGBA8, RGBA4,
RGB, RGB12, RGB8, RGB5, RGB332,
LUMINANCE_ALPHA,
RED, GREEN, BLUE, ALPHA, LUMINANCE
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. Otherwise, the size of the texels is determined by
the width of the components in the image file.
The number of components of the image file must match the format
specified; otherwise, it is an error and the format specification
is ignored.
<Scalar> wrap { repeat-definition }
<Scalar> wrapu { repeat-definition }
<Scalar> wrapv { 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".
<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:
POINT
LINEAR
BILINEAR
TRILINEAR
MIPMAP_POINT
MIPMAP_LINEAR
MIPMAP_BILINEAR
MIPMAP_TRILINEAR
ADD_DETAIL
MODULATE_DETAIL
<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
<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 filename ends in .rgba or the format is RGBA12. If
alpha-type is ON, it means to enable the default transparency,
even if the image filename does not end in .rgba. 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.
<Transform> { transform-definition }
This specifies a 2-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
defines a 2-d 3x3 matrix. The 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 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
}
The transform definition might also include the following scalar:
<Scalar> animated { 1 }
If this is set, it indicates the matrix may be animated by a
matrix channel, like a joint. At present, this flag is not used;
eventually, it may be used to define an arbitrary texture
coordinate animation.
<Material> name { [scalars] }
This defines a set of material attributes that may later be
referenced with <MRef> { name }.
At present, no material attributes have been implemented.
<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.
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> { u v [morph-list] }
This gives the texture coordinates of the vertex. This must be
specified if a texture is to be mapped onto this geometry. As
before, morph-list is an optional list of <DUV> entries.
In addition to the above, when the vertex serves as a control
vertex for a parametric curve the following attributes may be
supplied:
<Char*> continuity-type { type }
This has meaning for a Bezier curve only. It indicates the type
of continuity that should be forced for the given CV: cut, free,
g1, or smooth. This only applies to the end CV's of each curve
segment: every third CV.
<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 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>.
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.
<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 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.
<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 GeomBinFixed, 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 no bin scalar is specified, the default is a bin named "fixed",
which is a GeomBinFixed object that always exists by default.
<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, which is meaningful only when antialiasing
is in effect. The default is 1.0.
<Line> name {
[attributes]
<VertexRef> {
indices
<Ref> { pool-name }
}
}
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. As with a PointLight,
normals, textures, colors, draw-order, and the "thick" attribute are
all valid.
PARAMETRIC DESCRIPTION ENTRIES
The following entries define parametric curves and surfaces.
Generally, the player 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 show code. However, the player can
create visible representations of these parametrics to aid
visualization.
These entries might also have meaning to tools outside of the player,
such as a smart polygon mesher.
In general, dynamic attributes such as morphs and joint assignment are
legal for the control vertices of the following parametrics, but the
player doesn't support them and will always create static curves and
surfaces. Non-player tools, however, may respect them.
<BezierCurve> name {
[attributes]
[ <TLengths> { t1 t2 t3 ... } ]
<VertexRef> { indices <Ref> { pool-name } }
}
A Bezier curve will generally be used to describe a motion path
(though NURBS curves can be used for this purpose as well; see
below). The player translates <BezierCurve> entries into Hermite
curves internally.
Bezier curves can have any number of dimensions from one to three.
Accordingly, the referenced vertices may be defined for x, x y, or x
y z. All vertices should be defined over the same number of
dimensions.
A Bezier curve consists of a sequence of curve segments defined by
four vertices taken three at a time. The first four vertices define
the first curve segment, the vertices four through seven define the
second curve segment, and so on. The total number of vertices must
be one more than a multiple of three.
<TLengths> is a list of (n-1)/3 values, where n is the number of
Bezier control vertices. Each value corresponds to the length in
parametric space of the corresponding curve segment; the total curve
is defined over the parametric range [0,sum(TLengths)]. If this
entry is omitted, the curve will be defined over the range [0,1].
The following attributes may be defined:
<Char*> 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, the player 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.
Bezier control vertices may also be given color and/or morph
attributes (though the player ignores these), but <Normal> and <UV>
entries do not apply to Bezier vertices.
Each control vertex may optionally be given a continuity type,
defined with a "<Char*> continuity-type { type }" within the
<Vertex> entry. The type may be one of Cut, Free, G1, or Smooth.
This enforces the respective continuity restriction on the
neighboring vertices.
<NURBSCurve> {
[attributes]
<Order> { order }
<Knots> { knot-list }
<VertexRef> { indices <Ref> { pool-name } }
}
A NURBS curve is a more general parametric than a Bezier curve. It
can be used within the show anywhere a Bezier might have been used,
though a NURBS curve as the player creates it is more difficult to
modify at runtime.
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 valid attributes are the same for a <NURBSCurve> as that for a
<BezierCurve>, above. Similarly, NURBS vertices may be given color
and/or morph attributes.
<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 the player 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> { ... } ... ]
}
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.
Formerly, the target name must have been a nonnegative integer, but
this restriction no longer applies.
The following types of morph offsets may be defined, within their
corresponding attribute entries (an older, still supported, syntax
defined the target name after the first curly brace, instead of before
it):
<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.
<DUV> target { u v }
A texture-coordinate delta, valid within a <UV> entry (within a
<Vertex> entry). The given 2-valued 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
pfGroup nodes in the scene graph. 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 }
<Global> { boolean-value }
These two attributes are lexically equivalent, and indicate that
this group begins a character. An xpfCharacter node will be created
for this group.
<Dart> { dart-type }
This is another syntax for the <Dart> flag. The dart-type string
should be one of either "async" or "sync". This tells the egg
loader to optimize the character for asynchronous or synchronous
animation, respectively. In the absence of this dart-type, the
egg loader will choose the most general.
<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 pfSwitch node, 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 pfSequence node instead, which automatically cycles through its
children.
GROUP SCALARS
<Scalar> fps { frame-rate }
This specifies the rate of animation for a pfSequence (created
when the Switch flag is specified, see above). A value of zero
indicates a pfSwitch should be created instead.
<Scalar> no_fog { boolean-value }
This specifies that geometry at or below this node should not be
affected by fog. It will be created with the appropriate GeoState
to have fog disabled.
<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> write_through { boolean-value }
If this is present and boolean-value is non-zero, it places the
geometry at this level and below in a special drawing bin that is
drawn first and with the z-buffer set to write-through. This is
an optimization to avoid the initial screen clear when rendering a
completely enclosed scene; the flag should be set on the enclosing
geometry, which must be convex.
<Scalar> post_lp { boolean-value }
If this is present and boolean-value is non-zero, it places the
geometry at this level and below in a drawing bin that is drawn
after everything else in the scene, including light points. This
must be done particularly for semitransparent geometry which must
not obscure light points.
<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> 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.
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. If "fade" is
specified, it enables fade-LOD, and specifies the distance over
which to fade between this level of detail and the next-closer
one.
<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.
InverseSphere
The geometry represents a sphere with the normal inverted, to
make a hollow spherical shell.
Geode
The geometry is not a collision surface after all, but is in
fact true geometry. This is intended to be used in conjunction
with one or more flags to define collision properties for normal
geometry.
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.
solid
This has meaning only when the type is Polygon or Polyset. This
creates the polygon(s) as "solid" polygons, meaning no mover is
allowed to occupy the space immediately behind them. In the
absence of this flag, once a mover passes completely through a
polygon it is considered no longer intersecting with it.
center
Sets the collide-center property on the collision solid, so that
it collides with the center point of each mover, disregarding
the mover's radius. This implies "solid".
turnstile
Sets the turnstile property on the collision solid, so that
movers approaching from behind the solid will smoothly pass
through instead of being forcefully yanked to the front. This
is intended to implement a one-way wall, through which players
can go forwards but not back. Presently, this is only
implemented for planes, polygons, and polysets.
<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.
solidpoly
This is equivalent to <Collide> { Polyset descend solid }. See
the description of the "solid" property, above.
turnstile
This is equivalent to <Collide> { Polyset descend turnstile }. See
the description of the "turnstile" property, above.
trigger
This is equivalent to <Collide> { Polyset descend intangible }.
The geometry defined at this root and below defines an invisible
trigger surface.
eye-trigger
Equivalent to <Collide> { Polyset descend intangible center }.
This defines a trigger polygon whose point of collision is the
center of the mover; presumably this polygon will be used to
trigger visibility events.
bubble
Equivalent to <Collide> { Sphere keep descend }. A collision
bubble is placed around the geometry, which is otherwise
unchanged.
missile
Equivalent to <Collide> missile { Sphere keep descend event }. The
geometry defined at this root and below defines a missile
object, which will be surrounded by a collision sphere and named
"missile".
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 modelling tools.
<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 defines a 3-d transform when it
appears within the context of a node, while it defines a 2-d
transform (and has correspondingly different entries) when it
appears within the context of a texture.
<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.
<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 Performer 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 reference group's transform.
<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 the player to
the tree as a whole.
Bundles may only contain tables; tables may contain more tables,
bundles, or any one of the following (<Scalar> and <Char*> 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$Anim> name {
<Scalar> fps { 24 }
<Char*> order { sphrt }
<Char*> contents { ijkphrxyz }
<V> { values }
}
This is a table of matrix transforms, one per frame, such as may
be applied to a joint. The "contents" string consists of a subset
of the letters "ijkphrxyz", where each letter corresponds to a
column of the table; <V> is a list of numbers of length(contents)
* num_frames. Each letter of the contents string corresponds to a
type of transformation:
i, j, k - scale in x, y, z directions, respectively
p, h, r - rotate by pitch, heading, roll
x, y, z - translate in x, y, z directions
The net transformation matrix specified by each row of the table
is defined as the net effect of each of the individual columns'
transform, according to the corresponding letter in the contents
string. The order the transforms are applied is defined by the
order string:
s - all scale transforms
p, h, r - individual rotate transforms
t - all translation transforms
<Xfm$Anim_S$> name {
<Scalar> fps { 24 }
<Char*> order { sphrt }
<S$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 in the old player development to save memory
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 it is relative to the directory in which the current egg
file was found. If no directory prefix is specified, the current
egg file's directory is searched first, and then $PFPATH is
searched.
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