int flattenBVHTree(BVHBuildNode node, ref int offset)
{
LinearBVHNode linearNode = nodes[offset];
linearNode.bounds = node.bounds;
int myOffset = offset++;
if (node.nShapes > 0)
{
Debug.Assert(node.childLeft != null && node.childRight != null);
linearNode.ShapesOffset = node.firstPrimOffset;
linearNode.nShapes = (byte)node.nShapes;
}
else
{
// Creater interior flattened BVH node
linearNode.axis = (byte)node.splitAxis;
linearNode.nShapes = 0;
flattenBVHTree(node.childLeft, ref offset);
linearNode.secondChildOffset = flattenBVHTree(node.childRight, ref offset);
}
return(myOffset);
}
bool Intersect(Ray ray, ref LFloat isect)
{
if (nodes == null || nodes.Count == 0)
{
return(false);
}
bool hit = false;
LVector3 invDir = new LVector3(1 / ray.d.x, 1 / ray.d.y, 1 / ray.d.z);
int[] dirIsNeg = new int[3] {
invDir.x < 0 ? 1 : 0,
invDir.y < 0 ? 1 : 0,
invDir.z < 0 ? 1 : 0
};
// Follow ray through BVH nodes to find Shape intersections
int todoOffset = 0, nodeNum = 0;
int[] todo = new int[64];
LFloat tmin = LFloat.zero;
LFloat tmax = LFloat.zero;
while (true)
{
LinearBVHNode node = nodes[nodeNum];
// Check ray against BVH node
if (IntersectP(node.bounds, ray, invDir, dirIsNeg, tmin, tmax))
{
if (node.nShapes > 0)
{
// Intersect ray with Shapes in leaf BVH node
for (int i = 0; i < node.nShapes; ++i)
{
if (Shapes[node.ShapesOffset + i].TestWith(ray, ref isect))
{
hit = true;
}
}
if (todoOffset == 0)
{
break;
}
nodeNum = todo[--todoOffset];
}
else
{
// Put far BVH node on _todo_ stack, advance to near node
if (dirIsNeg[node.axis] != 0)
{
todo[todoOffset++] = nodeNum + 1;
nodeNum = node.secondChildOffset;
}
else
{
todo[todoOffset++] = node.secondChildOffset;
nodeNum = nodeNum + 1;
}
}
}
else
{
if (todoOffset == 0)
{
break;
}
nodeNum = todo[--todoOffset];
}
}
return(hit);
}
bool IntersectP(Ray ray, LFloat tmin, LFloat tmax)
{
if (nodes == null || nodes.Count == 0)
{
return(false);
}
LVector3 invDir = new LVector3(1 / ray.d.x, 1 / ray.d.y, 1 / ray.d.z);
int[] dirIsNeg = new int[3] {
invDir.x < 0 ? 1 : 0,
invDir.y < 0 ? 1 : 0,
invDir.z < 0 ? 1 : 0
};
int[] todo = new int[64]; //最大堆栈数
int todoOffset = 0, nodeNum = 0;
while (true)
{
LinearBVHNode node = nodes[nodeNum];
if (IntersectP(node.bounds, ray, invDir, dirIsNeg, tmin, tmax))
{
// Process BVH node _node_ for traversal
if (node.nShapes > 0)
{
for (int i = 0; i < node.nShapes; ++i)
{
if (Shapes[node.ShapesOffset + i].TestWith(ray))
{
return(true);
}
}
if (todoOffset == 0)
{
break;
}
nodeNum = todo[--todoOffset];
}
else
{
if (dirIsNeg[node.axis] != 0)
{
/// second child first
todo[todoOffset++] = nodeNum + 1;
nodeNum = node.secondChildOffset;
}
else
{
todo[todoOffset++] = node.secondChildOffset;
nodeNum = nodeNum + 1;
}
}
}
else
{
if (todoOffset == 0)
{
break;
}
nodeNum = todo[--todoOffset];
}
}
return(false);
}