bullet3/Extras/ConvexDecomposition/bestfitobb.cpp

#include "float_math.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <assert.h>

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		THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS' AND ANY EXPRESS OR IMPLIED WARRANTIES,
		INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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// http://codesuppository.blogspot.com
//
// mailto: jratcliff@infiniplex.net
//
// http://www.amillionpixels.us
//

#include "bestfitobb.h"
#include "float_math.h"

// computes the OBB for this set of points relative to this transform matrix.
void computeOBB(unsigned int vcount,const float *points,unsigned int pstride,float *sides,const float *matrix)
{
  const char *src = (const char *) points;

  float bmin[3] = { 1e9, 1e9, 1e9 };
  float bmax[3] = { -1e9, -1e9, -1e9 };

  for (unsigned int i=0; i<vcount; i++)
  {
    const float *p = (const float *) src;
    float t[3];

    fm_inverseRT(matrix, p, t ); // inverse rotate translate

    if ( t[0] < bmin[0] ) bmin[0] = t[0];
    if ( t[1] < bmin[1] ) bmin[1] = t[1];
    if ( t[2] < bmin[2] ) bmin[2] = t[2];

    if ( t[0] > bmax[0] ) bmax[0] = t[0];
    if ( t[1] > bmax[1] ) bmax[1] = t[1];
    if ( t[2] > bmax[2] ) bmax[2] = t[2];

    src+=pstride;
  }


  sides[0] = bmax[0];
  sides[1] = bmax[1];
  sides[2] = bmax[2];

  if ( fabsf(bmin[0]) > sides[0] ) sides[0] = fabsf(bmin[0]);
  if ( fabsf(bmin[1]) > sides[1] ) sides[1] = fabsf(bmin[1]);
  if ( fabsf(bmin[2]) > sides[2] ) sides[2] = fabsf(bmin[2]);

  sides[0]*=2.0f;
  sides[1]*=2.0f;
  sides[2]*=2.0f;

}

void computeBestFitOBB(unsigned int vcount,const float *points,unsigned int pstride,float *sides,float *matrix)
{

  float bmin[3];
  float bmax[3];

  fm_getAABB(vcount,points,pstride,bmin,bmax);

  float center[3];

  center[0] = (bmax[0]-bmin[0])*0.5f + bmin[0];
  center[1] = (bmax[1]-bmin[1])*0.5f + bmin[1];
  center[2] = (bmax[2]-bmin[2])*0.5f + bmin[2];

  float ax = 0;
  float ay = 0;
  float az = 0;

  float sweep =  45.0f; // 180 degree sweep on all three axes.
  float steps =   8.0f; // 16 steps on each axis.

  float bestVolume = 1e9;
  float angle[3]={0.f,0.f,0.f};

  while ( sweep >= 1 )
  {

    bool found = false;

    float stepsize = sweep / steps;

    for (float x=ax-sweep; x<=ax+sweep; x+=stepsize)
    {
      for (float y=ay-sweep; y<=ay+sweep; y+=stepsize)
      {
        for (float z=az-sweep; z<=az+sweep; z+=stepsize)
        {
          float pmatrix[16];

          fm_eulerMatrix( x*FM_DEG_TO_RAD, y*FM_DEG_TO_RAD, z*FM_DEG_TO_RAD, pmatrix );

          pmatrix[3*4+0] = center[0];
          pmatrix[3*4+1] = center[1];
          pmatrix[3*4+2] = center[2];

          float psides[3];

          computeOBB( vcount, points, pstride, psides, pmatrix );

          float volume = psides[0]*psides[1]*psides[2]; // the volume of the cube

          if ( volume <= bestVolume )
          {
            bestVolume = volume;

            sides[0] = psides[0];
            sides[1] = psides[1];
            sides[2] = psides[2];

            angle[0] = ax;
            angle[1] = ay;
            angle[2] = az;

            memcpy(matrix,pmatrix,sizeof(float)*16);
            found = true; // yes, we found an improvement.
          }
        }
      }
    }

    if ( found )
    {

      ax = angle[0];
      ay = angle[1];
      az = angle[2];

      sweep*=0.5f; // sweep 1/2 the distance as the last time.
    }
    else
    {
      break; // no improvement, so just
    }

  }

}