public bool GetIntersection(GeoRay3 ray, ref GeoInsectPointArrayInfo intersection, bool occlusion)
{
intersection.mIsIntersect = false;
intersection.mLength = 999999999.0f;
intersection.mHitObject2 = null;
int closer, other;
BVHTraversal[] todo = new BVHTraversal[64];
todo[0] = new BVHTraversal();
int stackptr = 0;
todo[stackptr].mIndex = 0;
todo[stackptr].mLength = -9999999.0f;
while (stackptr >= 0)
{
int ni = todo[stackptr].mIndex;
float near = todo[stackptr].mLength;
stackptr--;
BVHFlatNode3 node = mFlatTreeList[ni];
//if (near > intersection.mLength) // a bug here. may ignore closer object
// continue;
// 对叶节点做相交测试
if (node.mRightOffset == 0)
{
bool hit = false;
for (int o = 0; o < node.mLeafCount; ++o)
{
GeoInsectPointArrayInfo current = new GeoInsectPointArrayInfo();
BVHObject3 obj = mBuildPrims[(int)node.mStartIndex + o];
hit = obj.IsIntersect(ref ray, ref current);
if (hit)
{
if (occlusion)
{
intersection = current;
return(true);
}
if (current.mLength < intersection.mLength)
{
intersection = current;
}
}
}
}
else
{
closer = ni + 1;
other = ni + (int)node.mRightOffset;
// 对父结点做测试
GeoInsectPointArrayInfo in1 = new GeoInsectPointArrayInfo();
GeoInsectPointArrayInfo in2 = new GeoInsectPointArrayInfo();
bool hitc0 = GeoRayUtils.IsRayInsectAABB3(ray.mOrigin, ray.mDirection, mFlatTreeList[closer].mBox.mMin, mFlatTreeList[closer].mBox.mMax, ref in1);
bool hitc1 = GeoRayUtils.IsRayInsectAABB3(ray.mOrigin, ray.mDirection, mFlatTreeList[other].mBox.mMin, mFlatTreeList[other].mBox.mMax, ref in2);
if (hitc0 && hitc1)
{
float l0 = (in1.mHitGlobalPoint[0] - ray.mOrigin).magnitude;
float l2 = (in2.mHitGlobalPoint[0] - ray.mOrigin).magnitude;
if (l2 < l0)
{
float temp = l0;
l0 = l2;
l2 = temp;
int itemp = closer;
closer = other;
other = itemp;
}
todo[++stackptr] = new BVHTraversal(other, l2);
todo[++stackptr] = new BVHTraversal(closer, l0);
}
else if (hitc0)
{
float l0 = (in1.mHitGlobalPoint[0] - ray.mOrigin).magnitude;
todo[++stackptr] = new BVHTraversal(closer, l0);
}
else if (hitc1)
{
float l2 = (in2.mHitGlobalPoint[0] - ray.mOrigin).magnitude;
todo[++stackptr] = new BVHTraversal(other, l2);
}
}
}
if (intersection.mHitObject2 != null)
{
intersection.mHitGlobalPoint.Clear();
intersection.mHitGlobalPoint.mPointArray.Add(ray.mOrigin + ray.mDirection * intersection.mLength);
intersection.mIsIntersect = true;
}
return(intersection.mHitObject2 != null);
}
public void Build()
{
int stackptr = 0;
uint Untouched = 0xffffffff;
uint TouchedTwice = 0xfffffffd;
PREALLOC[stackptr].mStart = 0;
PREALLOC[stackptr].mEnd = (uint)mBuildPrims.Count;
PREALLOC[stackptr].mParent = 0xfffffffc;
stackptr++;
List <BVHFlatNode3> buildnodes = new List <BVHFlatNode3>(mBuildPrims.Count * 2);
while (stackptr > 0)
{
BVHBuildEntry bnode = PREALLOC[--stackptr];
uint start = bnode.mStart;
uint end = bnode.mEnd;
uint nPrims = end - start;
mNumNodes++;
BVHFlatNode3 node = new BVHFlatNode3();
node.mStartIndex = start;
node.mLeafCount = nPrims;
node.mRightOffset = Untouched;
BVHAABB3 bb = new BVHAABB3(mBuildPrims[(int)start].GetAABB().mMin, mBuildPrims[(int)start].GetAABB().mMax);
BVHAABB3 bc = new BVHAABB3(mBuildPrims[(int)start].GetCenter(), mBuildPrims[(int)start].GetCenter());
for (uint p = start + 1; p < end; ++p)
{
bb.ExpandToInclude(mBuildPrims[(int)p].GetAABB());
bc.ExpandToInclude(mBuildPrims[(int)p].GetCenter());
}
node.mBox = bb;
if (nPrims <= mNodeMaxLeafSize)
{
node.mRightOffset = 0;
mNumLeafs++;
}
buildnodes.Add(node);
// 记录父节点关于右孩子结点相对父结点的偏移值mRightOffset
// 第一次为左孩子，相对父结点的偏移值为1
// 每个父节点最多被两次 hit
if (bnode.mParent != 0xfffffffc)
{
buildnodes[(int)bnode.mParent].mRightOffset--;
if (buildnodes[(int)bnode.mParent].mRightOffset == TouchedTwice)
{
buildnodes[(int)bnode.mParent].mRightOffset = (uint)mNumNodes - 1 - bnode.mParent;
}
}
if (node.mRightOffset == 0)
{
continue;
}
// 选择合适的分割维度
uint split_dim = (uint)bc.MaxDimension();
float split_coord = 0.5f * (bc.mMin[(int)split_dim] + bc.mMax[(int)split_dim]);
uint mid = start;
// 交换 start 和 end 之间 的数据
for (uint i = start; i < end; ++i)
{
if (mBuildPrims[(int)i].GetCenter()[(int)split_dim] < split_coord && i != mid)
{
if (i != mid)
{
BVHObject3 temp = mBuildPrims[(int)i];
mBuildPrims[(int)i] = mBuildPrims[(int)mid];
mBuildPrims[(int)mid] = temp;
}
++mid;
}
}
if (mid == start || mid == end)
{
mid = start + (end - start) / 2;
}
// 右孩子
PREALLOC[stackptr].mStart = mid;
PREALLOC[stackptr].mEnd = end;
PREALLOC[stackptr].mParent = (uint)mNumNodes - 1;
stackptr++;
// 左孩子
PREALLOC[stackptr].mStart = start;
PREALLOC[stackptr].mEnd = mid;
PREALLOC[stackptr].mParent = (uint)mNumNodes - 1;
stackptr++;
}
if (mFlatTreeList != null)
{
mFlatTreeList.Clear();
}
mFlatTreeList = new List <BVHFlatNode3>(mNumNodes);
for (uint n = 0; n < mNumNodes; ++n)
{
mFlatTreeList.Add(buildnodes[(int)n]);
}
}