111 lines
3.8 KiB
C++
111 lines
3.8 KiB
C++
// Filename: linearFrictionForce.cxx
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// Created by: charles (23Jun00)
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//
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////////////////////////////////////////////////////////////////////
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//
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// PANDA 3D SOFTWARE
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// Copyright (c) Carnegie Mellon University. All rights reserved.
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//
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// All use of this software is subject to the terms of the revised BSD
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// license. You should have received a copy of this license along
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// with this source code in a file named "LICENSE."
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//
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////////////////////////////////////////////////////////////////////
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#include "linearFrictionForce.h"
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#include "config_physics.h"
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TypeHandle LinearFrictionForce::_type_handle;
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////////////////////////////////////////////////////////////////////
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// Function : LinearFrictionForce
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// Access : Public
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// Description : Constructor
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////////////////////////////////////////////////////////////////////
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LinearFrictionForce::
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LinearFrictionForce(float coef, float a, bool m) :
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LinearForce(a, m) {
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set_coef(coef);
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}
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////////////////////////////////////////////////////////////////////
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// Function : LinearFrictionForce
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// Access : Public
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// Description : copy constructor
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////////////////////////////////////////////////////////////////////
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LinearFrictionForce::
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LinearFrictionForce(const LinearFrictionForce ©) :
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LinearForce(copy) {
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_coef = copy._coef;
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}
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////////////////////////////////////////////////////////////////////
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// Function : LinearFrictionForce
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// Access : Public
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// Description : destructor
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////////////////////////////////////////////////////////////////////
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LinearFrictionForce::
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~LinearFrictionForce() {
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}
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////////////////////////////////////////////////////////////////////
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// Function : make_copy
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// Access : Public
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// Description : copier
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////////////////////////////////////////////////////////////////////
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LinearForce *LinearFrictionForce::
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make_copy() {
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return new LinearFrictionForce(*this);
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}
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////////////////////////////////////////////////////////////////////
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// Function : LinearFrictionForce
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// Access : Public
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// Description : Constructor
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////////////////////////////////////////////////////////////////////
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LVector3f LinearFrictionForce::
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get_child_vector(const PhysicsObject* po) {
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LVector3f v = po->get_velocity();
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assert(_coef>=0.0f && _coef<=1.0f);
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// Create a force vector in the opposite direction of v:
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LVector3f friction = v * -_coef;
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physics_debug(" v "<<v<<" len "<<v.length()
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<<" friction "<<friction<<" len "<<friction.length()
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<<" dot "<<(normalize(v).dot(normalize(friction))));
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assert(friction.almost_equal(LVector3f::zero())
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|| IS_NEARLY_EQUAL(normalize(v).dot(normalize(friction)), -1.0f));
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// cary said to cap this at zero so that friction can't reverse
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// your direction, but it seems to me that if you're computing:
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// v + (-v * _coef), _coef in [0, 1]
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// that this will always be greater than or equal to zero.
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return friction;
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}
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////////////////////////////////////////////////////////////////////
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// Function : output
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// Access : Public
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// Description : Write a string representation of this instance to
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// <out>.
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////////////////////////////////////////////////////////////////////
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void LinearFrictionForce::
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output(ostream &out) const {
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#ifndef NDEBUG //[
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out<<"LinearFrictionForce";
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#endif //] NDEBUG
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}
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////////////////////////////////////////////////////////////////////
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// Function : write
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// Access : Public
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// Description : Write a string representation of this instance to
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// <out>.
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////////////////////////////////////////////////////////////////////
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void LinearFrictionForce::
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write(ostream &out, unsigned int indent) const {
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#ifndef NDEBUG //[
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out.width(indent); out<<""; out<<"LinearFrictionForce:\n";
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out.width(indent+2); out<<""; out<<"_coef "<<_coef<<":\n";
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LinearForce::write(out, indent+2);
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#endif //] NDEBUG
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}
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