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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		and/or other materials provided with the distribution.

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		be used to endorse or promote products derived from this software without specific prior written permission.

		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
		DISCLAIMED. IN NO EVENT SHALL THE INTEL OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
		EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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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
		}
	}
}