217 lines
7 KiB
C
Executable file
217 lines
7 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 cpFloat
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defaultSpringForce(cpDampedSpring *spring, cpFloat dist){
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return (spring->restLength - dist)*spring->stiffness;
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}
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static void
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preStep(cpDampedSpring *spring, cpFloat dt)
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{
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cpBody *a = spring->constraint.a;
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cpBody *b = spring->constraint.b;
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spring->r1 = cpTransformVect(a->transform, cpvsub(spring->anchorA, a->cog));
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spring->r2 = cpTransformVect(b->transform, cpvsub(spring->anchorB, b->cog));
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cpVect delta = cpvsub(cpvadd(b->p, spring->r2), cpvadd(a->p, spring->r1));
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cpFloat dist = cpvlength(delta);
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spring->n = cpvmult(delta, 1.0f/(dist ? dist : INFINITY));
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cpFloat k = k_scalar(a, b, spring->r1, spring->r2, spring->n);
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cpAssertSoft(k != 0.0, "Unsolvable spring.");
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spring->nMass = 1.0f/k;
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spring->target_vrn = 0.0f;
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spring->v_coef = 1.0f - cpfexp(-spring->damping*dt*k);
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// apply spring force
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cpFloat f_spring = spring->springForceFunc((cpConstraint *)spring, dist);
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cpFloat j_spring = spring->jAcc = f_spring*dt;
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apply_impulses(a, b, spring->r1, spring->r2, cpvmult(spring->n, j_spring));
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}
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static void applyCachedImpulse(cpDampedSpring *spring, cpFloat dt_coef){}
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static void
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applyImpulse(cpDampedSpring *spring, cpFloat dt)
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{
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cpBody *a = spring->constraint.a;
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cpBody *b = spring->constraint.b;
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cpVect n = spring->n;
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cpVect r1 = spring->r1;
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cpVect r2 = spring->r2;
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// compute relative velocity
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cpFloat vrn = normal_relative_velocity(a, b, r1, r2, n);
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// compute velocity loss from drag
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cpFloat v_damp = (spring->target_vrn - vrn)*spring->v_coef;
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spring->target_vrn = vrn + v_damp;
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cpFloat j_damp = v_damp*spring->nMass;
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spring->jAcc += j_damp;
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apply_impulses(a, b, spring->r1, spring->r2, cpvmult(spring->n, j_damp));
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}
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static cpFloat
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getImpulse(cpDampedSpring *spring)
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{
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return spring->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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cpDampedSpring *
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cpDampedSpringAlloc(void)
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{
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return (cpDampedSpring *)cpcalloc(1, sizeof(cpDampedSpring));
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}
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cpDampedSpring *
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cpDampedSpringInit(cpDampedSpring *spring, cpBody *a, cpBody *b, cpVect anchorA, cpVect anchorB, cpFloat restLength, cpFloat stiffness, cpFloat damping)
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{
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cpConstraintInit((cpConstraint *)spring, &klass, a, b);
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spring->anchorA = anchorA;
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spring->anchorB = anchorB;
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spring->restLength = restLength;
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spring->stiffness = stiffness;
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spring->damping = damping;
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spring->springForceFunc = (cpDampedSpringForceFunc)defaultSpringForce;
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spring->jAcc = 0.0f;
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return spring;
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}
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cpConstraint *
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cpDampedSpringNew(cpBody *a, cpBody *b, cpVect anchorA, cpVect anchorB, cpFloat restLength, cpFloat stiffness, cpFloat damping)
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{
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return (cpConstraint *)cpDampedSpringInit(cpDampedSpringAlloc(), a, b, anchorA, anchorB, restLength, stiffness, damping);
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}
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cpBool
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cpConstraintIsDampedSpring(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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cpDampedSpringGetAnchorA(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->anchorA;
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}
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void
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cpDampedSpringSetAnchorA(cpConstraint *constraint, cpVect anchorA)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->anchorA = anchorA;
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}
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cpVect
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cpDampedSpringGetAnchorB(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->anchorB;
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}
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void
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cpDampedSpringSetAnchorB(cpConstraint *constraint, cpVect anchorB)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->anchorB = anchorB;
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}
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cpFloat
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cpDampedSpringGetRestLength(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->restLength;
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}
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void
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cpDampedSpringSetRestLength(cpConstraint *constraint, cpFloat restLength)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->restLength = restLength;
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}
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cpFloat
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cpDampedSpringGetStiffness(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->stiffness;
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}
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void
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cpDampedSpringSetStiffness(cpConstraint *constraint, cpFloat stiffness)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->stiffness = stiffness;
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}
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cpFloat
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cpDampedSpringGetDamping(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->damping;
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}
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void
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cpDampedSpringSetDamping(cpConstraint *constraint, cpFloat damping)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->damping = damping;
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}
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cpDampedSpringForceFunc
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cpDampedSpringGetSpringForceFunc(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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return ((cpDampedSpring *)constraint)->springForceFunc;
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}
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void
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cpDampedSpringSetSpringForceFunc(cpConstraint *constraint, cpDampedSpringForceFunc springForceFunc)
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{
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cpAssertHard(cpConstraintIsDampedSpring(constraint), "Constraint is not a damped spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedSpring *)constraint)->springForceFunc = springForceFunc;
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}
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