C++ (Cpp) Aabbの例

void BVHTree::BuildNode(BVHNode *node,
			const objPtr_t *objPtrs,
			const Aabb *objAabbs,
			std::vector<objPtr_t> &activeObjIdx)
{
	const int numTris = activeObjIdx.size();
	if (numTris <= 0) Error("BuildNode called with no elements in activeObjIndex.");

	if (numTris == 1) {
		MakeLeaf(node, objPtrs, activeObjIdx);
		return;
	}

	std::vector<int> splitSides(numTris);

	Aabb aabb;
	aabb.min = vector3d(FLT_MAX, FLT_MAX, FLT_MAX);
	aabb.max = vector3d(-FLT_MAX, -FLT_MAX, -FLT_MAX);

	for (int i=0; i<numTris; i++) {
		int idx = activeObjIdx[i];
		aabb.Update(objAabbs[idx].min);
		aabb.Update(objAabbs[idx].max);
	}
	node->numTris = numTris;
	node->aabb = aabb;

	Aabb splitBox = aabb;
	double splitPos;
	int splitAxis;
	int s1count, s2count;
	int attempt = 0;

	for (;;) {
		splitAxis = 0;

		vector3d boxSize = splitBox.max - splitBox.min;

		if (boxSize[1] > boxSize[0]) splitAxis = 1;
		if ((boxSize[2] > boxSize[1]) && (boxSize[2] > boxSize[0])) splitAxis = 2;

		// split pos in middle of splitBox
		splitPos = 0.5f * (splitBox.min[splitAxis] + splitBox.max[splitAxis]);
		s1count = 0, s2count = 0;

		for (int i=0; i<numTris; i++) {
			int idx = activeObjIdx[i];
			double mid = 0.5 * (objAabbs[idx].min[splitAxis] + objAabbs[idx].max[splitAxis]);
			if (mid < splitPos) {
				splitSides[i] = 0;
				s1count++;
			} else {
				splitSides[i] = 1;
				s2count++;
			}
		}

		if (s1count == numTris) {
			if (attempt < MAX_SPLITPOS_RETRIES) {
				// try splitting at average point
				splitBox.max[splitAxis] = splitPos;
				attempt++;
				continue;
			} else {
				MakeLeaf(node, objPtrs, activeObjIdx);
				return;
			}
		} else if (s2count == numTris) {
			if (attempt < MAX_SPLITPOS_RETRIES) {
				// try splitting at average point
				splitBox.min[splitAxis] = splitPos;
				attempt++;
				continue;
			} else {
				MakeLeaf(node, objPtrs, activeObjIdx);
				return;
			}
		}
		break;
	}

	std::vector<int> side[2];

	for (int i=0; i<numTris; i++) {
		side[splitSides[i]].push_back(activeObjIdx[i]);
	}

	// recurse!
	node->triIndicesStart = 0;
	node->kids[0] = AllocNode();
	node->kids[1] = AllocNode();

	BuildNode(node->kids[0], objPtrs, objAabbs, side[0]);
	BuildNode(node->kids[1], objPtrs, objAabbs, side[1]);
}