146 lines
4.2 KiB
C
Executable file
146 lines
4.2 KiB
C
Executable file
/* Copyright (c) 2013 Scott Lembcke and Howling Moon Software
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "chipmunk/chipmunk_private.h"
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static void
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preStep(cpGearJoint *joint, cpFloat dt)
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{
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cpBody *a = joint->constraint.a;
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cpBody *b = joint->constraint.b;
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// calculate moment of inertia coefficient.
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joint->iSum = 1.0f/(a->i_inv*joint->ratio_inv + joint->ratio*b->i_inv);
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// calculate bias velocity
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cpFloat maxBias = joint->constraint.maxBias;
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joint->bias = cpfclamp(-bias_coef(joint->constraint.errorBias, dt)*(b->a*joint->ratio - a->a - joint->phase)/dt, -maxBias, maxBias);
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}
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static void
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applyCachedImpulse(cpGearJoint *joint, cpFloat dt_coef)
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{
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cpBody *a = joint->constraint.a;
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cpBody *b = joint->constraint.b;
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cpFloat j = joint->jAcc*dt_coef;
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a->w -= j*a->i_inv*joint->ratio_inv;
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b->w += j*b->i_inv;
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}
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static void
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applyImpulse(cpGearJoint *joint, cpFloat dt)
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{
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cpBody *a = joint->constraint.a;
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cpBody *b = joint->constraint.b;
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// compute relative rotational velocity
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cpFloat wr = b->w*joint->ratio - a->w;
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cpFloat jMax = joint->constraint.maxForce*dt;
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// compute normal impulse
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cpFloat j = (joint->bias - wr)*joint->iSum;
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cpFloat jOld = joint->jAcc;
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joint->jAcc = cpfclamp(jOld + j, -jMax, jMax);
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j = joint->jAcc - jOld;
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// apply impulse
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a->w -= j*a->i_inv*joint->ratio_inv;
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b->w += j*b->i_inv;
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}
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static cpFloat
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getImpulse(cpGearJoint *joint)
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{
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return cpfabs(joint->jAcc);
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}
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static const cpConstraintClass klass = {
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(cpConstraintPreStepImpl)preStep,
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(cpConstraintApplyCachedImpulseImpl)applyCachedImpulse,
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(cpConstraintApplyImpulseImpl)applyImpulse,
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(cpConstraintGetImpulseImpl)getImpulse,
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};
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cpGearJoint *
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cpGearJointAlloc(void)
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{
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return (cpGearJoint *)cpcalloc(1, sizeof(cpGearJoint));
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}
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cpGearJoint *
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cpGearJointInit(cpGearJoint *joint, cpBody *a, cpBody *b, cpFloat phase, cpFloat ratio)
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{
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cpConstraintInit((cpConstraint *)joint, &klass, a, b);
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joint->phase = phase;
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joint->ratio = ratio;
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joint->ratio_inv = 1.0f/ratio;
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joint->jAcc = 0.0f;
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return joint;
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}
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cpConstraint *
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cpGearJointNew(cpBody *a, cpBody *b, cpFloat phase, cpFloat ratio)
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{
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return (cpConstraint *)cpGearJointInit(cpGearJointAlloc(), a, b, phase, ratio);
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}
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cpBool
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cpConstraintIsGearJoint(const cpConstraint *constraint)
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{
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return (constraint->klass == &klass);
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}
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cpFloat
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cpGearJointGetPhase(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsGearJoint(constraint), "Constraint is not a ratchet joint.");
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return ((cpGearJoint *)constraint)->phase;
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}
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void
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cpGearJointSetPhase(cpConstraint *constraint, cpFloat phase)
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{
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cpAssertHard(cpConstraintIsGearJoint(constraint), "Constraint is not a ratchet joint.");
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cpConstraintActivateBodies(constraint);
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((cpGearJoint *)constraint)->phase = phase;
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}
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cpFloat
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cpGearJointGetRatio(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsGearJoint(constraint), "Constraint is not a ratchet joint.");
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return ((cpGearJoint *)constraint)->ratio;
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}
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void
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cpGearJointSetRatio(cpConstraint *constraint, cpFloat ratio)
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{
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cpAssertHard(cpConstraintIsGearJoint(constraint), "Constraint is not a ratchet joint.");
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cpConstraintActivateBodies(constraint);
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((cpGearJoint *)constraint)->ratio = ratio;
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((cpGearJoint *)constraint)->ratio_inv = 1.0f/ratio;
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}
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