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/* Copyright (c) 2007 Scott Lembcke
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "stdlib.h"
#include "chipmunk.h"
#ifdef __cplusplus
extern "C" {
#endif
void cpInitCollisionFuncs(void);
#ifdef __cplusplus
}
#endif
void
cpInitChipmunk(void)
{
cpInitCollisionFuncs();
}
cpFloat
cpMomentForCircle(cpFloat m, cpFloat r1, cpFloat r2, cpVect offset)
{
return (1.0f/2.0f)*m*(r1*r1 + r2*r2) + m*cpvdot(offset, offset);
}
cpFloat
cpMomentForPoly(cpFloat m, const int numVerts, cpVect *verts, cpVect offset)
{
cpVect *tVerts = (cpVect *)calloc(numVerts, sizeof(cpVect));
for(int i=0; i<numVerts; i++)
tVerts[i] = cpvadd(verts[i], offset);
cpFloat sum1 = 0.0f;
cpFloat sum2 = 0.0f;
for(int i=0; i<numVerts; i++){
cpVect v1 = tVerts[i];
cpVect v2 = tVerts[(i+1)%numVerts];
cpFloat a = cpvcross(v2, v1);
cpFloat b = cpvdot(v1, v1) + cpvdot(v1, v2) + cpvdot(v2, v2);
sum1 += a*b;
sum2 += a;
}
free(tVerts);
return (m*sum1)/(6.0f*sum2);
}
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