public Normal3 Sample(Random random)
{
ISphere sphere = new UnitSphere(Position3.Origin);
Normal3 direction = ((Direction3)sphere.SurfacePosition(random)).Normalized();
return(IDirection3.InSameClosedHemisphere(Orientation, direction) ? direction : -direction);
}
/// <summary> The SBVH thinks it can get a better split </summary>
/// <returns>A better or equal split than the normal BVH would</returns>
protected override Split?GetSplit()
{
Split?bvhSplit = base.GetSplit();
// TODO: Introduce Alpha to just use regular split
Split? sbvhSplit;
IDirection3 size = Shape.BoundingBox.Size;
if (size.X > size.Y && size.X > size.Z)
{
sbvhSplit = BestSpatialBinSplit(Normal3.UnitX, AxisAlignedPlane.X, v => v.X);
}
else if (size.Y > size.Z)
{
sbvhSplit = BestSpatialBinSplit(Normal3.UnitY, AxisAlignedPlane.Y, v => v.Y);
}
else
{
sbvhSplit = BestSpatialBinSplit(Normal3.UnitZ, AxisAlignedPlane.Z, v => v.Z);
}
if (bvhSplit == null)
{
return(sbvhSplit);
}
if (sbvhSplit == null)
{
return(bvhSplit);
}
float bvhSplitSAH = bvhSplit.SurfaceAreaHeuristic;
float sbvhSplitSAH = sbvhSplit.SurfaceAreaHeuristic;
return(bvhSplitSAH < sbvhSplitSAH ? bvhSplit : sbvhSplit);
}
/// <summary> Get the best split for this node </summary>
/// <returns>The best split for this BVH node</returns>
protected virtual Split?GetSplit()
{
if (Bin && Items.Count > BinAmount)
{
IDirection3 size = Shape.BoundingBox.Size;
if (size.X > size.Y && size.X > size.Z)
{
return(BestBinSplit(Normal3.UnitX, v => v.X));
}
else if (size.Y > size.Z)
{
return(BestBinSplit(Normal3.UnitY, v => v.Y));
}
else
{
return(BestBinSplit(Normal3.UnitZ, v => v.Z));
}
}
else
{
return(BestSweepSplit());
}
}
public bool Contains(Normal3 sample) => IDirection3.InSameClosedHemisphere(Orientation, sample);
public double ProbabilityDensity(Normal3 sample) => Math.Abs(IDirection3.Dot(Orientation, sample));
