private Face connectHalfEdges(
HalfEdge hedgePrev, HalfEdge hedge)
{
Face discardedFace = null;
if (hedgePrev.oppositeFace() == hedge.oppositeFace())
{ // then there is a redundant edge that we can get rid off
Face oppFace = hedge.oppositeFace();
HalfEdge hedgeOpp;
if (hedgePrev == he0)
{
he0 = hedge;
}
if (oppFace.numVertices() == 3)
{ // then we can get rid of the opposite face altogether
hedgeOpp = hedge.getOpposite().prev.getOpposite();
oppFace.mark = DELETED;
discardedFace = oppFace;
}
else
{
hedgeOpp = hedge.getOpposite().next;
if (oppFace.he0 == hedgeOpp.prev)
{
oppFace.he0 = hedgeOpp;
}
hedgeOpp.prev = hedgeOpp.prev.prev;
hedgeOpp.prev.next = hedgeOpp;
}
hedge.prev = hedgePrev.prev;
hedge.prev.next = hedge;
hedge.opposite = hedgeOpp;
hedgeOpp.opposite = hedge;
// oppFace was modified, so need to recompute
oppFace.computeNormalAndCentroid();
}
else
{
hedgePrev.next = hedge;
hedge.prev = hedgePrev;
}
return(discardedFace);
}
private HalfEdge addAdjoiningFace(Vertex eyeVtx, HalfEdge he)
{
Face face = Face.createTriangle(
eyeVtx, he.tail(), he.head());
faces.Add(face);
face.getEdge(-1).setOpposite(he.getOpposite());
return(face.getEdge(0));
}
public int mergeAdjacentFace(HalfEdge hedgeAdj,
Face[] discarded)
{
Face oppFace = hedgeAdj.oppositeFace();
int numDiscarded = 0;
discarded[numDiscarded++] = oppFace;
oppFace.mark = DELETED;
HalfEdge hedgeOpp = hedgeAdj.getOpposite();
HalfEdge hedgeAdjPrev = hedgeAdj.prev;
HalfEdge hedgeAdjNext = hedgeAdj.next;
HalfEdge hedgeOppPrev = hedgeOpp.prev;
HalfEdge hedgeOppNext = hedgeOpp.next;
while (hedgeAdjPrev.oppositeFace() == oppFace)
{
hedgeAdjPrev = hedgeAdjPrev.prev;
hedgeOppNext = hedgeOppNext.next;
}
while (hedgeAdjNext.oppositeFace() == oppFace)
{
hedgeOppPrev = hedgeOppPrev.prev;
hedgeAdjNext = hedgeAdjNext.next;
}
HalfEdge hedge;
for (hedge = hedgeOppNext; hedge != hedgeOppPrev.next; hedge = hedge.next)
{
hedge.face = this;
}
if (hedgeAdj == he0)
{
he0 = hedgeAdjNext;
}
// handle the half edges at the head
Face discardedFace;
discardedFace = connectHalfEdges(hedgeOppPrev, hedgeAdjNext);
if (discardedFace != null)
{
discarded[numDiscarded++] = discardedFace;
}
// handle the half edges at the tail
discardedFace = connectHalfEdges(hedgeAdjPrev, hedgeOppNext);
if (discardedFace != null)
{
discarded[numDiscarded++] = discardedFace;
}
computeNormalAndCentroid();
checkConsistency();
return(numDiscarded);
}
public void checkConsistency()
{
// do a sanity check on the face
HalfEdge hedge = he0;
double maxd = 0;
int numv = 0;
if (numVerts < 3)
{
throw new Exception(
"degenerate face: " + getVertexString());
}
do
{
HalfEdge hedgeOpp = hedge.getOpposite();
if (hedgeOpp == null)
{
throw new Exception(
"face " + getVertexString() + ": " +
"unreflected half edge " + hedge.getVertexString());
}
else if (hedgeOpp.getOpposite() != hedge)
{
throw new Exception(
"face " + getVertexString() + ": " +
"opposite half edge " + hedgeOpp.getVertexString() +
" has opposite " +
hedgeOpp.getOpposite().getVertexString());
}
if (hedgeOpp.head() != hedge.tail() ||
hedge.head() != hedgeOpp.tail())
{
throw new Exception(
"face " + getVertexString() + ": " +
"half edge " + hedge.getVertexString() +
" reflected by " + hedgeOpp.getVertexString());
}
Face oppFace = hedgeOpp.face;
if (oppFace == null)
{
throw new Exception(
"face " + getVertexString() + ": " +
"no face on half edge " + hedgeOpp.getVertexString());
}
else if (oppFace.mark == DELETED)
{
throw new Exception(
"face " + getVertexString() + ": " +
"opposite face " + oppFace.getVertexString() +
" not on hull");
}
double d = Math.Abs(distanceToPlane(hedge.head().pnt));
if (d > maxd)
{
maxd = d;
}
numv++;
hedge = hedge.next;
}while (hedge != he0);
if (numv != numVerts)
{
throw new Exception(
"face " + getVertexString() + " numVerts=" + numVerts + " should be " + numv);
}
}