153 lines
4.6 KiB
C
Executable file
153 lines
4.6 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(cpPivotJoint *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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joint->r1 = cpTransformVect(a->transform, cpvsub(joint->anchorA, a->cog));
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joint->r2 = cpTransformVect(b->transform, cpvsub(joint->anchorB, b->cog));
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// Calculate mass tensor
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joint-> k = k_tensor(a, b, joint->r1, joint->r2);
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// calculate bias velocity
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cpVect delta = cpvsub(cpvadd(b->p, joint->r2), cpvadd(a->p, joint->r1));
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joint->bias = cpvclamp(cpvmult(delta, -bias_coef(joint->constraint.errorBias, dt)/dt), joint->constraint.maxBias);
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}
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static void
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applyCachedImpulse(cpPivotJoint *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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apply_impulses(a, b, joint->r1, joint->r2, cpvmult(joint->jAcc, dt_coef));
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}
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static void
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applyImpulse(cpPivotJoint *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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cpVect r1 = joint->r1;
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cpVect r2 = joint->r2;
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// compute relative velocity
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cpVect vr = relative_velocity(a, b, r1, r2);
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// compute normal impulse
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cpVect j = cpMat2x2Transform(joint->k, cpvsub(joint->bias, vr));
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cpVect jOld = joint->jAcc;
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joint->jAcc = cpvclamp(cpvadd(joint->jAcc, j), joint->constraint.maxForce*dt);
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j = cpvsub(joint->jAcc, jOld);
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// apply impulse
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apply_impulses(a, b, joint->r1, joint->r2, j);
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}
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static cpFloat
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getImpulse(cpConstraint *joint)
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{
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return cpvlength(((cpPivotJoint *)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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cpPivotJoint *
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cpPivotJointAlloc(void)
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{
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return (cpPivotJoint *)cpcalloc(1, sizeof(cpPivotJoint));
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}
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cpPivotJoint *
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cpPivotJointInit(cpPivotJoint *joint, cpBody *a, cpBody *b, cpVect anchorA, cpVect anchorB)
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{
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cpConstraintInit((cpConstraint *)joint, &klass, a, b);
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joint->anchorA = anchorA;
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joint->anchorB = anchorB;
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joint->jAcc = cpvzero;
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return joint;
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}
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cpConstraint *
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cpPivotJointNew2(cpBody *a, cpBody *b, cpVect anchorA, cpVect anchorB)
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{
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return (cpConstraint *)cpPivotJointInit(cpPivotJointAlloc(), a, b, anchorA, anchorB);
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}
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cpConstraint *
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cpPivotJointNew(cpBody *a, cpBody *b, cpVect pivot)
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{
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cpVect anchorA = (a ? cpBodyWorldToLocal(a, pivot) : pivot);
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cpVect anchorB = (b ? cpBodyWorldToLocal(b, pivot) : pivot);
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return cpPivotJointNew2(a, b, anchorA, anchorB);
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}
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cpBool
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cpConstraintIsPivotJoint(const cpConstraint *constraint)
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{
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return (constraint->klass == &klass);
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}
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cpVect
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cpPivotJointGetAnchorA(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsPivotJoint(constraint), "Constraint is not a pivot joint.");
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return ((cpPivotJoint *)constraint)->anchorA;
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}
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void
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cpPivotJointSetAnchorA(cpConstraint *constraint, cpVect anchorA)
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{
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cpAssertHard(cpConstraintIsPivotJoint(constraint), "Constraint is not a pivot joint.");
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cpConstraintActivateBodies(constraint);
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((cpPivotJoint *)constraint)->anchorA = anchorA;
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}
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cpVect
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cpPivotJointGetAnchorB(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsPivotJoint(constraint), "Constraint is not a pivot joint.");
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return ((cpPivotJoint *)constraint)->anchorB;
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}
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void
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cpPivotJointSetAnchorB(cpConstraint *constraint, cpVect anchorB)
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{
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cpAssertHard(cpConstraintIsPivotJoint(constraint), "Constraint is not a pivot joint.");
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cpConstraintActivateBodies(constraint);
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((cpPivotJoint *)constraint)->anchorB = anchorB;
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}
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