179 lines
6 KiB
C
Executable file
179 lines
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 cpFloat
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defaultSpringTorque(cpDampedRotarySpring *spring, cpFloat relativeAngle){
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return (relativeAngle - spring->restAngle)*spring->stiffness;
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}
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static void
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preStep(cpDampedRotarySpring *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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cpFloat moment = a->i_inv + b->i_inv;
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cpAssertSoft(moment != 0.0, "Unsolvable spring.");
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spring->iSum = 1.0f/moment;
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spring->w_coef = 1.0f - cpfexp(-spring->damping*dt*moment);
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spring->target_wrn = 0.0f;
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// apply spring torque
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cpFloat j_spring = spring->springTorqueFunc((cpConstraint *)spring, a->a - b->a)*dt;
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spring->jAcc = j_spring;
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a->w -= j_spring*a->i_inv;
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b->w += j_spring*b->i_inv;
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}
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static void applyCachedImpulse(cpDampedRotarySpring *spring, cpFloat dt_coef){}
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static void
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applyImpulse(cpDampedRotarySpring *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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// compute relative velocity
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cpFloat wrn = a->w - b->w;//normal_relative_velocity(a, b, r1, r2, n) - spring->target_vrn;
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// compute velocity loss from drag
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// not 100% certain this is derived correctly, though it makes sense
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cpFloat w_damp = (spring->target_wrn - wrn)*spring->w_coef;
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spring->target_wrn = wrn + w_damp;
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//apply_impulses(a, b, spring->r1, spring->r2, cpvmult(spring->n, v_damp*spring->nMass));
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cpFloat j_damp = w_damp*spring->iSum;
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spring->jAcc += j_damp;
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a->w += j_damp*a->i_inv;
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b->w -= j_damp*b->i_inv;
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}
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static cpFloat
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getImpulse(cpDampedRotarySpring *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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cpDampedRotarySpring *
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cpDampedRotarySpringAlloc(void)
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{
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return (cpDampedRotarySpring *)cpcalloc(1, sizeof(cpDampedRotarySpring));
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}
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cpDampedRotarySpring *
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cpDampedRotarySpringInit(cpDampedRotarySpring *spring, cpBody *a, cpBody *b, cpFloat restAngle, cpFloat stiffness, cpFloat damping)
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{
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cpConstraintInit((cpConstraint *)spring, &klass, a, b);
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spring->restAngle = restAngle;
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spring->stiffness = stiffness;
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spring->damping = damping;
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spring->springTorqueFunc = (cpDampedRotarySpringTorqueFunc)defaultSpringTorque;
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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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cpDampedRotarySpringNew(cpBody *a, cpBody *b, cpFloat restAngle, cpFloat stiffness, cpFloat damping)
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{
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return (cpConstraint *)cpDampedRotarySpringInit(cpDampedRotarySpringAlloc(), a, b, restAngle, stiffness, damping);
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}
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cpBool
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cpConstraintIsDampedRotarySpring(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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cpDampedRotarySpringGetRestAngle(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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return ((cpDampedRotarySpring *)constraint)->restAngle;
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}
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void
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cpDampedRotarySpringSetRestAngle(cpConstraint *constraint, cpFloat restAngle)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedRotarySpring *)constraint)->restAngle = restAngle;
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}
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cpFloat
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cpDampedRotarySpringGetStiffness(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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return ((cpDampedRotarySpring *)constraint)->stiffness;
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}
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void
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cpDampedRotarySpringSetStiffness(cpConstraint *constraint, cpFloat stiffness)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedRotarySpring *)constraint)->stiffness = stiffness;
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}
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cpFloat
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cpDampedRotarySpringGetDamping(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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return ((cpDampedRotarySpring *)constraint)->damping;
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}
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void
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cpDampedRotarySpringSetDamping(cpConstraint *constraint, cpFloat damping)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedRotarySpring *)constraint)->damping = damping;
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}
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cpDampedRotarySpringTorqueFunc
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cpDampedRotarySpringGetSpringTorqueFunc(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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return ((cpDampedRotarySpring *)constraint)->springTorqueFunc;
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}
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void
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cpDampedRotarySpringSetSpringTorqueFunc(cpConstraint *constraint, cpDampedRotarySpringTorqueFunc springTorqueFunc)
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{
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cpAssertHard(cpConstraintIsDampedRotarySpring(constraint), "Constraint is not a damped rotary spring.");
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cpConstraintActivateBodies(constraint);
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((cpDampedRotarySpring *)constraint)->springTorqueFunc = springTorqueFunc;
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}
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