/// <summary>
/// Get an ordered list of the faces to render based on the camera position.
/// </summary>
/// <param name="node"></param>
/// <param name="meshToViewTransform"></param>
/// <param name="invMeshToViewTransform"></param>
/// <param name="faceRenderOrder"></param>
public static IEnumerable<int> GetFacesInVisibiltyOrder(Mesh mesh, BspNode root, Matrix4X4 meshToViewTransform, Matrix4X4 invMeshToViewTransform)
{
var renderOrder = new Stack<BspNode>(new BspNode[] { root.RenderOrder(mesh, meshToViewTransform, invMeshToViewTransform) });
do
{
var lastBack = renderOrder.Peek().BackNode;
while (lastBack != null
&& lastBack.Index != -1)
{
renderOrder.Peek().BackNode = null;
renderOrder.Push(lastBack.RenderOrder(mesh, meshToViewTransform, invMeshToViewTransform));
lastBack = renderOrder.Peek().BackNode;
}
var node = renderOrder.Pop();
if (node.Index != -1)
{
yield return node.Index;
}
var lastFront = node.FrontNode;
if (lastFront != null && lastFront.Index != -1)
{
renderOrder.Push(lastFront.RenderOrder(mesh, meshToViewTransform, invMeshToViewTransform));
}
}
while (renderOrder.Any());
}
public static BspNode RenderOrder(this BspNode node, Mesh mesh, Matrix4X4 meshToViewTransform, Matrix4X4 invMeshToViewTransform)
{
var faceNormalInViewSpace = mesh.Faces[node.Index].normal.TransformNormalInverse(invMeshToViewTransform);
var pointOnFaceInViewSpace = mesh.Vertices[mesh.Faces[node.Index].v0].Transform(meshToViewTransform);
var infrontOfFace = faceNormalInViewSpace.Dot(pointOnFaceInViewSpace) < 0;
if (infrontOfFace)
{
return new BspNode()
{
Index = node.Index,
BackNode = node.BackNode,
FrontNode = node.FrontNode
};
}
else
{
return new BspNode()
{
Index = node.Index,
BackNode = node.FrontNode,
FrontNode = node.BackNode
};
}
}
public static BspNode RenderOrder(this BspNode node, List <Face> meshFaces, Matrix4X4 meshToViewTransform, Matrix4X4 invMeshToViewTransform)
{
var faceNormalInViewSpace = Vector3.TransformNormalInverse(meshFaces[node.Index].Normal, invMeshToViewTransform);
var pointOnFaceInViewSpace = Vector3.Transform(meshFaces[node.Index].firstFaceEdge.FirstVertex.Position, meshToViewTransform);
var infrontOfFace = Vector3.Dot(faceNormalInViewSpace, pointOnFaceInViewSpace) < 0;
if (infrontOfFace)
{
return(new BspNode()
{
Index = node.Index,
BackNode = node.BackNode,
FrontNode = node.FrontNode
});
}
else
{
return(new BspNode()
{
Index = node.Index,
BackNode = node.FrontNode,
FrontNode = node.BackNode
});
}
}
/// <summary>
/// This function will search for the first face that produces no polygon cuts
/// and split the tree on it. If it can't find a non-cutting face,
/// it will split on the face that minimizes the area that it divides.
/// </summary>
/// <param name="mesh"></param>
/// <returns></returns>
public static BspNode Create(Mesh mesh, int maxFacesToTest = 10, bool tryToBalanceTree = false)
{
BspNode root = new BspNode();
var faces = new List <Face>(mesh.Faces);
CreateNoSplitingFast(mesh.Faces, root, faces, maxFacesToTest, tryToBalanceTree);
return(root);
}
/// <summary>
/// This function will search for the first face that produces no polygon cuts
/// and split the tree on it. If it can't find a non-cutting face,
/// it will split on the face that minimizes the area that it divides.
/// </summary>
/// <param name="mesh"></param>
/// <returns></returns>
public static BspNode Create(Mesh mesh, int maxFacesToTest = 10, bool tryToBalanceTree = false)
{
BspNode root = new BspNode();
var sourceFaces = Enumerable.Range(0, mesh.Faces.Count).ToList();
var faces = Enumerable.Range(0, mesh.Faces.Count).ToList();
CreateNoSplittingFast(mesh, sourceFaces, root, faces, maxFacesToTest, tryToBalanceTree);
return root;
}
private static void CreateNoSplittingFast(Mesh mesh, List <int> sourceFaces, BspNode node, List <int> faces, int maxFacesToTest, bool tryToBalanceTree)
{
if (faces.Count == 0)
{
return;
}
int bestFaceIndex = -1;
double smallestCrossingArrea = double.MaxValue;
int bestBalance = int.MaxValue;
// find the first face that does not split anything
int step = Math.Max(1, faces.Count / maxFacesToTest);
for (int i = 0; i < faces.Count; i += step)
{
// calculate how much of polygons cross this face
(double crossingArrea, int balance) = CalculateCrossingArea(mesh, i, faces, smallestCrossingArrea);
// keep track of the best face so far
if (crossingArrea < smallestCrossingArrea)
{
smallestCrossingArrea = crossingArrea;
bestBalance = balance;
bestFaceIndex = i;
if (crossingArrea == 0 &&
!tryToBalanceTree)
{
break;
}
}
else if (crossingArrea == smallestCrossingArrea &&
balance < bestBalance)
{
// the crossing area is the same but the tree balance is better
bestBalance = balance;
bestFaceIndex = i;
}
}
node.Index = sourceFaces.IndexOf(faces[bestFaceIndex]);
// put the behind stuff in a list
var backFaces = new List <int>();
var frontFaces = new List <int>();
CreateBackAndFrontFaceLists(mesh, bestFaceIndex, faces, backFaces, frontFaces);
CreateNoSplittingFast(mesh, sourceFaces, node.BackNode = new BspNode(), backFaces, maxFacesToTest, tryToBalanceTree);
CreateNoSplittingFast(mesh, sourceFaces, node.FrontNode = new BspNode(), frontFaces, maxFacesToTest, tryToBalanceTree);
}
