124 lines
3.4 KiB
C
Executable file
124 lines
3.4 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(cpSimpleMotor *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 + b->i_inv);
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}
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static void
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applyCachedImpulse(cpSimpleMotor *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;
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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(cpSimpleMotor *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 - a->w + joint->rate;
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cpFloat jMax = joint->constraint.maxForce*dt;
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// compute normal impulse
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cpFloat j = -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;
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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(cpSimpleMotor *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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cpSimpleMotor *
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cpSimpleMotorAlloc(void)
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{
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return (cpSimpleMotor *)cpcalloc(1, sizeof(cpSimpleMotor));
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}
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cpSimpleMotor *
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cpSimpleMotorInit(cpSimpleMotor *joint, cpBody *a, cpBody *b, cpFloat rate)
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{
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cpConstraintInit((cpConstraint *)joint, &klass, a, b);
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joint->rate = rate;
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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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cpSimpleMotorNew(cpBody *a, cpBody *b, cpFloat rate)
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{
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return (cpConstraint *)cpSimpleMotorInit(cpSimpleMotorAlloc(), a, b, rate);
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}
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cpBool
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cpConstraintIsSimpleMotor(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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cpSimpleMotorGetRate(const cpConstraint *constraint)
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{
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cpAssertHard(cpConstraintIsSimpleMotor(constraint), "Constraint is not a SimpleMotor.");
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return ((cpSimpleMotor *)constraint)->rate;
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}
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void
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cpSimpleMotorSetRate(cpConstraint *constraint, cpFloat rate)
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{
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cpAssertHard(cpConstraintIsSimpleMotor(constraint), "Constraint is not a SimpleMotor.");
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cpConstraintActivateBodies(constraint);
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((cpSimpleMotor *)constraint)->rate = rate;
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}
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