private BVHInsertion FindBestLocalInsertion(ImplicitBoundingBoxNode aabb, float inheritedCost)
{
float newArea = GetAABBArea(BoundingBox.CreateMerged(Bound, aabb.Bound));
float asSiblingCost = 2.0f * newArea;
float areaDiff = newArea - GetAABBArea(Bound);
if (IsLeaf)
{
BVHInsertion leafInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsSibling);
leafInsertion.Cost = asSiblingCost + inheritedCost;
leafInsertion.LocationInheritance = inheritedCost;
return(leafInsertion);
}
float asChildCost = mChildren.Count * areaDiff + newArea;
BVHInsertion bestInsertion;
if (asSiblingCost < asChildCost)
{
bestInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsSibling);
bestInsertion.Cost = asSiblingCost + inheritedCost;
}
else
{
bestInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsChild);
bestInsertion.Cost = asChildCost + inheritedCost;
}
bestInsertion.LocationInheritance = mChildren.Count * areaDiff + inheritedCost;
return(bestInsertion);
}
public void InsertNodeIntoBVH(ImplicitBoundingBoxNode aabb)
{
// See http://tog.acm.org/resources/RTNews/html/rtnews3a.html#art6 for algorithm details.
BVHInsertion bestInsertion = FindBestLocalInsertion(aabb, 0.0f);
BVHInsertion bestDeepInsertion = FindBestDeepInsertion(aabb, bestInsertion.LocationInheritance, bestInsertion.Cost);
if (bestDeepInsertion.Cost < bestInsertion.Cost)
{
bestInsertion = bestDeepInsertion;
}
// Perform insertion.
switch (bestInsertion.Method)
{
case BVHInsertion.InsertionMethod.AsSibling:
ImplicitBoundingBoxNode copyOfLocation = new ImplicitBoundingBoxNode(bestInsertion.Location);
bestInsertion.Location.IsLeaf = false;
bestInsertion.Location.mChildren = new List <SceneNode>();
bestInsertion.Location.AddChild(copyOfLocation);
bestInsertion.Location.AddChild(aabb);
break;
case BVHInsertion.InsertionMethod.AsChild:
bestInsertion.Location.AddChild(aabb);
break;
}
// The Bound must be recomputed after this operation.
bestInsertion.Location.RecalculateBound();
}
private BVHInsertion FindBestDeepInsertion(ImplicitBoundingBoxNode aabb, float inheritance, float costToBeat)
{
if (IsLeaf)
{
return(BVHInsertion.WorstInsertion);
}
// Find best local insertion cost for each child:
BVHInsertion bestChildInsertion = BVHInsertion.WorstInsertion;
foreach (ImplicitBoundingBoxNode child in mChildren.OfType <ImplicitBoundingBoxNode>())
{
BVHInsertion altChildInsertion = child.FindBestLocalInsertion(aabb, inheritance);
if (altChildInsertion.Cost < bestChildInsertion.Cost)
{
bestChildInsertion = altChildInsertion;
}
}
// Which child had the best local cost? Was it better than our local cost? If so, update the costToBeat.
if (bestChildInsertion.Cost < costToBeat)
{
costToBeat = bestChildInsertion.Cost;
}
// Finally, explore the deeper insertion costs of that child...
// Make sure the child's inheritance permits improvement before recursing.
if (bestChildInsertion.LocationInheritance < costToBeat)
{
BVHInsertion bestChildDeepInsertion = bestChildInsertion.Location.FindBestDeepInsertion(aabb, bestChildInsertion.LocationInheritance, costToBeat);
// Compare the deep insertion cost with our best so far...
if (bestChildDeepInsertion.Cost < bestChildInsertion.Cost)
{
return(bestChildDeepInsertion);
}
}
return(bestChildInsertion);
}
static BVHInsertion()
{
WorstInsertion = new BVHInsertion(null, BVHInsertion.InsertionMethod.AsChild);
WorstInsertion.Cost = Single.MaxValue;
WorstInsertion.LocationInheritance = Single.MaxValue;
}
private BVHInsertion FindBestLocalInsertion(ImplicitBoundingBoxNode aabb, float inheritedCost)
{
float newArea = GetAABBArea(BoundingBox.CreateMerged(Bound, aabb.Bound));
float asSiblingCost = 2.0f * newArea;
float areaDiff = newArea - GetAABBArea(Bound);
if (IsLeaf)
{
BVHInsertion leafInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsSibling);
leafInsertion.Cost = asSiblingCost + inheritedCost;
leafInsertion.LocationInheritance = inheritedCost;
return leafInsertion;
}
float asChildCost = mChildren.Count * areaDiff + newArea;
BVHInsertion bestInsertion;
if (asSiblingCost < asChildCost)
{
bestInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsSibling);
bestInsertion.Cost = asSiblingCost + inheritedCost;
}
else
{
bestInsertion = new BVHInsertion(this, BVHInsertion.InsertionMethod.AsChild);
bestInsertion.Cost = asChildCost + inheritedCost;
}
bestInsertion.LocationInheritance = mChildren.Count * areaDiff + inheritedCost;
return bestInsertion;
}
static BVHInsertion()
{
WorstInsertion = new BVHInsertion(null, BVHInsertion.InsertionMethod.AsChild);
WorstInsertion.Cost = Single.MaxValue;
WorstInsertion.LocationInheritance = Single.MaxValue;
}
