public void Construct(Aggregate aggregate)
{
Material = ((IIntersectable)aggregate).Material;
Aggregate objects = new IntersectableList();
foreach (IIntersectable intersectable in aggregate.GetObjects())
{
objects.Add(intersectable);
}
BoundingBox = ((IIntersectable)aggregate).BoundingBox;
//Calculate max treed depth = 8+1.3*log(n);
maxTreeDepth = (int)Math.Ceiling(8 + (1.3 * Math.Log(objects.Intersectables.Count)));
RootNode = new BspNode();
//Kick off the recursive tree construction
RootNode.BuildSubTree(objects, BoundingBox, maxTreeDepth, 0);
}
public HitRecord Intersect(Ray ray)
{
#region BSP Tree Traversal
BspNode node = RootNode;
HitRecord hit = null;
Stack <BspStackItem> nodeStack = new Stack <BspStackItem>();
BspNode first, second;
float[] boxIntersections = node.BoundingBox.Intersect(ray);
if (boxIntersections == null)
{
return(null);
}
float tmin = boxIntersections[0];
float tmax = boxIntersections[1];
float isect = float.MaxValue;
while (node != null)
{
if (isect < tmin)
{
return(hit);
}
if (!node.IsLeaf)
{
//process interior node
//tsplit = compute ray-split plane intersection
//<order of children>
//<process of children>
float tSplit = node.DistanceToSplitPlane(ray);
//Order children
if (ray.Origin[node.Axis] < node.PlanePos)
{
first = node.RightNode;
second = node.LeftNode;
}
else
{
first = node.LeftNode;
second = node.RightNode;
}
//Process children
if (tSplit < 0 || tSplit > tmax || (tSplit == 0.0f && ray.Direction[node.Axis] > 0))
{
node = first;
}
else if (tSplit < tmin || (tSplit == 0.0f && ray.Direction[node.Axis] < 0))
{
node = second;
}
else
{
node = first;
BspStackItem item = new BspStackItem(second, tSplit, tmax);
nodeStack.Push(item);
tmax = tSplit;
}
}
else
{
//Intersection = first intersection in leaf
HitRecord tmpHitRecord = node.Intersectables.Intersect(ray);;
if (tmpHitRecord != null)
{
isect = tmpHitRecord.Distance;
hit = tmpHitRecord;
}
if (nodeStack.Count > 0)
{
BspStackItem sItem = nodeStack.Pop();
node = sItem.Node;
tmin = sItem.Tmin;
tmax = sItem.Tmax;
}
else
{
node = null;
}
}
}
return(hit);
#endregion
#region simple tree traversal
/**
* Traverse the tree and do intersection
*/
/*Stack<BspNode> nodesToVisit = new Stack<BspNode>();
* nodesToVisit.Push(RootNode);
* HitRecord hit = null;
* HitRecord tempHit;
* while (nodesToVisit.Count > 0)
* {
* BspNode currentNode = nodesToVisit.Pop();
* if (currentNode.IsLeaf)
* {
* foreach (IIntersectable intersectable in currentNode.Intersectables)
* {
* tempHit = intersectable.Intersect(ray);
* if (tempHit != null)
* {
* if (hit == null) hit = tempHit;
* else if (tempHit.Distance < hit.Distance) hit = tempHit;
* }
* }
* }
* else
* {
* nodesToVisit.Push(currentNode.LeftNode);
* nodesToVisit.Push(currentNode.RightNode);
* }
* }
* return hit;*/
#endregion
}
public BspStackItem(BspNode node, float tmin, float tmax)
{
Node = node;
Tmin = tmin;
Tmax = tmax;
}
public void BuildSubTree(Aggregate intersectables, IBoundingBox boundingBox, int maxTreeDepth, int currentTreeDetph)
{
Intersectables = intersectables;
BoundingBox = boundingBox;
if (Intersectables.GetNumberOfComponents() <= 5 || currentTreeDetph == maxTreeDepth)
{
IsLeaf = true;
}
else
{
Aggregate leftIntersectables = new IntersectableList();
Aggregate rightIntersectables = new IntersectableList();
//Find the maximal Axis
Axis = 0;
float max = BoundingBox.Dimension.X;
if (BoundingBox.Dimension.Y > max)
{
Axis = 1;
}
if (BoundingBox.Dimension.Z > max)
{
Axis = 2;
}
//Axis = currentTreeDetph % 3;
PlanePos = BoundingBox.MaxVector[Axis] - (BoundingBox.MaxVector[Axis] - BoundingBox.MinVector[Axis]) / 2;
Vector3 leftMin = Vector3.Zero;
Vector3 leftMax = Vector3.Zero;
Vector3 rightMin = Vector3.Zero;
Vector3 rightMax = Vector3.Zero;
switch (Axis)
{
case 0:
leftMin = new Vector3(PlanePos, BoundingBox.MinVector.Y, BoundingBox.MinVector.Z);
leftMax = new Vector3(BoundingBox.MaxVector);
rightMin = new Vector3(BoundingBox.MinVector);
rightMax = new Vector3(PlanePos, BoundingBox.MaxVector.Y, BoundingBox.MaxVector.Z);
break;
case 1:
leftMin = new Vector3(BoundingBox.MinVector.X, PlanePos, BoundingBox.MinVector.Z);
leftMax = new Vector3(BoundingBox.MaxVector);
rightMin = new Vector3(BoundingBox.MinVector);
rightMax = new Vector3(BoundingBox.MaxVector.X, PlanePos, BoundingBox.MaxVector.Z);
break;
case 2:
leftMin = new Vector3(BoundingBox.MinVector.X, BoundingBox.MinVector.Y, PlanePos);
leftMax = new Vector3(BoundingBox.MaxVector);
rightMin = new Vector3(BoundingBox.MinVector);
rightMax = new Vector3(BoundingBox.MaxVector.X, BoundingBox.MaxVector.Y, PlanePos);
break;
}
IBoundingBox leftBb = new AxisAlignedBoundingBox(leftMin, leftMax);
IBoundingBox rightBb = new AxisAlignedBoundingBox(rightMin, rightMax);
LeftNode = new BspNode();
RightNode = new BspNode();
foreach (IIntersectable intersectable in Intersectables.GetObjects())
{
if (intersectable.BoundingBox.Intersect(leftBb))
{
leftIntersectables.Add(intersectable);
}
if (intersectable.BoundingBox.Intersect(rightBb))
{
rightIntersectables.Add(intersectable);
}
}
LeftNode.BuildSubTree(leftIntersectables, leftBb, maxTreeDepth, currentTreeDetph + 1);
RightNode.BuildSubTree(rightIntersectables, rightBb, maxTreeDepth, currentTreeDetph + 1);
Intersectables = null; //Clear up the intersectables in non leaf nodes to save space
}
}
