173 lines
5.2 KiB
C
Executable file
173 lines
5.2 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(cpPinJoint *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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cpVect delta = cpvsub(cpvadd(b->p, joint->r2), cpvadd(a->p, joint->r1));
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cpFloat dist = cpvlength(delta);
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joint->n = cpvmult(delta, 1.0f/(dist ? dist : (cpFloat)INFINITY));
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// calculate mass normal
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joint->nMass = 1.0f/k_scalar(a, b, joint->r1, joint->r2, joint->n);
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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)*(dist - joint->dist)/dt, -maxBias, maxBias);
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}
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static void
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applyCachedImpulse(cpPinJoint *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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cpVect j = cpvmult(joint->n, joint->jnAcc*dt_coef);
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apply_impulses(a, b, joint->r1, joint->r2, j);
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}
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static void
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applyImpulse(cpPinJoint *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 n = joint->n;
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// compute relative velocity
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cpFloat vrn = normal_relative_velocity(a, b, joint->r1, joint->r2, n);
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cpFloat jnMax = joint->constraint.maxForce*dt;
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// compute normal impulse
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cpFloat jn = (joint->bias - vrn)*joint->nMass;
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cpFloat jnOld = joint->jnAcc;
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joint->jnAcc = cpfclamp(jnOld + jn, -jnMax, jnMax);
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jn = joint->jnAcc - jnOld;
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// apply impulse
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apply_impulses(a, b, joint->r1, joint->r2, cpvmult(n, jn));
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}
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static cpFloat
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getImpulse(cpPinJoint *joint)
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{
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return cpfabs(joint->jnAcc);
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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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cpPinJoint *
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cpPinJointAlloc(void)
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{
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return (cpPinJoint *)cpcalloc(1, sizeof(cpPinJoint));
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}
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cpPinJoint *
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cpPinJointInit(cpPinJoint *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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// STATIC_BODY_CHECK
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cpVect p1 = (a ? cpTransformPoint(a->transform, anchorA) : anchorA);
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cpVect p2 = (b ? cpTransformPoint(b->transform, anchorB) : anchorB);
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joint->dist = cpvlength(cpvsub(p2, p1));
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cpAssertWarn(joint->dist > 0.0, "You created a 0 length pin joint. A pivot joint will be much more stable.");
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joint->jnAcc = 0.0f;
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return joint;
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}
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cpConstraint *
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cpPinJointNew(cpBody *a, cpBody *b, cpVect anchorA, cpVect anchorB)
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{
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return (cpConstraint *)cpPinJointInit(cpPinJointAlloc(), a, b, anchorA, anchorB);
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}
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cpBool
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cpConstraintIsPinJoint(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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cpPinJointGetAnchorA(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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return ((cpPinJoint *)constraint)->anchorA;
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}
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void
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cpPinJointSetAnchorA(cpConstraint *constraint, cpVect anchorA)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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cpConstraintActivateBodies(constraint);
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((cpPinJoint *)constraint)->anchorA = anchorA;
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}
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cpVect
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cpPinJointGetAnchorB(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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return ((cpPinJoint *)constraint)->anchorB;
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}
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void
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cpPinJointSetAnchorB(cpConstraint *constraint, cpVect anchorB)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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cpConstraintActivateBodies(constraint);
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((cpPinJoint *)constraint)->anchorB = anchorB;
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}
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cpFloat
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cpPinJointGetDist(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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return ((cpPinJoint *)constraint)->dist;
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}
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void
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cpPinJointSetDist(cpConstraint *constraint, cpFloat dist)
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{
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cpAssertHard(cpConstraintIsPinJoint(constraint), "Constraint is not a pin joint.");
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cpConstraintActivateBodies(constraint);
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((cpPinJoint *)constraint)->dist = dist;
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}
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