/*
* Delete any degenerate faces with only two edges. WalkDirtyRegions()
* will catch almost all of these, but it won't catch degenerate faces
* produced by splice operations on already-processed edges.
* The two places this can happen are in FinishLeftRegions(), when
* we splice in a "temporary" edge produced by ConnectRightVertex(),
* and in CheckForLeftSplice(), where we splice already-processed
* edges to ensure that our dictionary invariants are not violated
* by numerical errors.
*
* In both these cases it is *very* dangerous to delete the offending
* edge at the time, since one of the routines further up the stack
* will sometimes be keeping a pointer to that edge.
*/
private static bool RemoveDegenerateFaces(Mesh mesh)
{
Face f, fNext;
HalfEdge e;
for (f = mesh.faceHead.nextFace; f != mesh.faceHead; f = fNext)
{
fNext = f.nextFace;
e = f.halfEdgeThisIsLeftFaceOf;
if (e.nextEdgeCCWAroundLeftFace == e)
{
throw new Exception();
}
if (e.nextEdgeCCWAroundLeftFace.nextEdgeCCWAroundLeftFace == e)
{
/* A face with only two edges */
AddWinding(e.nextEdgeCCWAroundOrigin, e);
Mesh.DeleteHalfEdge(e);
}
}
return true;
}
/* __gl_meshUnion( mesh1, mesh2 ) forms the union of all structures in
* both meshes, and returns the new mesh (the old meshes are destroyed).
*/
private Mesh meshUnion(Mesh mesh1, Mesh mesh2)
{
Face f1 = mesh1.faceHead;
ContourVertex v1 = mesh1.vertexHead;
HalfEdge e1 = mesh1.halfEdgeHead;
Face f2 = mesh2.faceHead;
ContourVertex v2 = mesh2.vertexHead;
HalfEdge e2 = mesh2.halfEdgeHead;
/* Add the faces, vertices, and edges of mesh2 to those of mesh1 */
if (f2.nextFace != f2)
{
f1.prevFace.nextFace = f2.nextFace;
f2.nextFace.prevFace = f1.prevFace;
f2.prevFace.nextFace = f1;
f1.prevFace = f2.prevFace;
}
if (v2.nextVertex != v2)
{
v1.prevVertex.nextVertex = v2.nextVertex;
v2.nextVertex.prevVertex = v1.prevVertex;
v2.prevVertex.nextVertex = v1;
v1.prevVertex = v2.prevVertex;
}
if (e2.nextHalfEdge != e2)
{
e1.otherHalfOfThisEdge.nextHalfEdge.otherHalfOfThisEdge.nextHalfEdge = e2.nextHalfEdge;
e2.nextHalfEdge.otherHalfOfThisEdge.nextHalfEdge = e1.otherHalfOfThisEdge.nextHalfEdge;
e2.otherHalfOfThisEdge.nextHalfEdge.otherHalfOfThisEdge.nextHalfEdge = e1;
e1.otherHalfOfThisEdge.nextHalfEdge = e2.otherHalfOfThisEdge.nextHalfEdge;
}
mesh2 = null;
return mesh1;
}
public void RenderMesh(Mesh mesh)
{
Face f;
/* Make a list of separate triangles so we can render them all at once */
lonelyTriList = null;
for (f = mesh.faceHead.nextFace; f != mesh.faceHead; f = f.nextFace)
{
f.marked = false;
}
for (f = mesh.faceHead.nextFace; f != mesh.faceHead; f = f.nextFace)
{
/* We examine all faces in an arbitrary order. Whenever we find
* an unprocessed face F, we output a group of faces including F
* whose size is maximum.
*/
if (f.isInterior && !f.marked)
{
RenderMaximumFaceGroup(f);
if (!f.marked)
{
throw new Exception();
}
}
}
if (lonelyTriList != null)
{
RenderLonelyTriangles(lonelyTriList);
lonelyTriList = null;
}
}
/************************ Boundary contour decomposition ******************/
/* Takes a mesh, and outputs one
* contour for each face marked "inside". The rendering output is
* provided as callbacks.
*/
public void RenderBoundary(Mesh mesh)
{
for (Face curFace = mesh.faceHead.nextFace; curFace != mesh.faceHead; curFace = curFace.nextFace)
{
if (curFace.isInterior)
{
CallBegin(TriangleListType.LineLoop);
HalfEdge curHalfEdge = curFace.halfEdgeThisIsLeftFaceOf;
do
{
CallVertex(curHalfEdge.originVertex.clientIndex);
curHalfEdge = curHalfEdge.nextEdgeCCWAroundLeftFace;
} while (curHalfEdge != curFace.halfEdgeThisIsLeftFaceOf);
CallEnd();
}
}
}
public void EndPolygon()
{
RequireState(ProcessingState.InPolygon);
processingState = ProcessingState.Dormant;
if (mesh == null)
{
if (!EdgeCallBackSet && callMesh == null)
{
/* Try some special code to make the easy cases go quickly
* (eg. convex polygons). This code does NOT handle multiple contours,
* intersections, edge flags, and of course it does not generate
* an explicit mesh either.
*/
if (RenderCache())
{
return;
}
}
EmptyCache(); /* could've used a label*/
}
/* Determine the polygon normal and project vertices onto the plane
* of the polygon.
*/
ProjectPolygon();
/* __gl_computeInterior( this ) computes the planar arrangement specified
* by the given contours, and further subdivides this arrangement
* into regions. Each region is marked "inside" if it belongs
* to the polygon, according to the rule given by this.windingRule.
* Each interior region is guaranteed to be monotone.
*/
ActiveRegion.ComputeInterior(this);
bool rc = true;
/* If the user wants only the boundary contours, we throw away all edges
* except those which separate the interior from the exterior.
* Otherwise we tessellate all the regions marked "inside".
*/
if (boundaryOnly)
{
rc = mesh.SetWindingNumber(1, true);
}
else
{
rc = mesh.TessellateInterior();
}
mesh.CheckMesh();
if (callBegin != null || callEnd != null
|| callVertex != null || callEdgeFlag != null)
{
if (boundaryOnly)
{
RenderBoundary(mesh); /* output boundary contours */
}
else
{
RenderMesh(mesh); /* output strips and fans */
}
}
if (callMesh != null)
{
/* Throw away the exterior faces, so that all faces are interior.
* This way the user doesn't have to check the "inside" flag,
* and we don't need to even reveal its existence. It also leaves
* the freedom for an implementation to not generate the exterior
* faces in the first place.
*/
mesh.DiscardExterior();
callMesh(mesh); /* user wants the mesh itself */
mesh = null;
return;
}
mesh = null;
}
public void EmptyCache()
{
VertexAndIndex[] v = simpleVertexCache;
mesh = new Mesh();
for (int i = 0; i < cacheCount; i++)
{
AddVertex(v[i].x, v[i].y, v[i].vertexIndex);
}
cacheCount = 0;
emptyCache = false;
}
public virtual void BeginPolygon()
{
RequireState(ProcessingState.Dormant);
processingState = ProcessingState.InPolygon;
cacheCount = 0;
emptyCache = false;
mesh = null;
}