/// <summary>
/// Check the upper and lower edges of the given region to see if
/// they intersect. If so, create the intersection and add it
/// to the data structures.
///
/// Returns TRUE if adding the new intersection resulted in a recursive
/// call to AddRightEdges(); in this case all "dirty" regions have been
/// checked for intersections, and possibly regUp has been deleted.
/// </summary>
private bool CheckForIntersect(ActiveRegion regUp)
{
ActiveRegion regLo = RegionBelow(regUp);
MeshUtils.Edge eUp = regUp._eUp;
MeshUtils.Edge eLo = regLo._eUp;
MeshUtils.Vertex orgUp = eUp._Org;
MeshUtils.Vertex orgLo = eLo._Org;
MeshUtils.Vertex dstUp = eUp._Dst;
MeshUtils.Vertex dstLo = eLo._Dst;
Debug.Assert(!Geom.VertEq(dstLo, dstUp));
Debug.Assert(Geom.EdgeSign(dstUp, _event, orgUp) <= 0.0f);
Debug.Assert(Geom.EdgeSign(dstLo, _event, orgLo) >= 0.0f);
Debug.Assert(orgUp != _event && orgLo != _event);
Debug.Assert(!regUp._fixUpperEdge && !regLo._fixUpperEdge);
if (orgUp == orgLo)
{
// right endpoints are the same
return(false);
}
double tMinUp = Math.Min(orgUp._t, dstUp._t);
double tMaxLo = Math.Max(orgLo._t, dstLo._t);
if (tMinUp > tMaxLo)
{
// t ranges do not overlap
return(false);
}
if (Geom.VertLeq(orgUp, orgLo))
{
if (Geom.EdgeSign(dstLo, orgUp, orgLo) > 0.0f)
{
return(false);
}
}
else
{
if (Geom.EdgeSign(dstUp, orgLo, orgUp) < 0.0f)
{
return(false);
}
}
// At this point the edges intersect, at least marginally
MeshUtils.Vertex isect = _pool.Get <MeshUtils.Vertex>();
Geom.EdgeIntersect(dstUp, orgUp, dstLo, orgLo, isect);
// The following properties are guaranteed:
Debug.Assert(Math.Min(orgUp._t, dstUp._t) <= isect._t);
Debug.Assert(isect._t <= Math.Max(orgLo._t, dstLo._t));
Debug.Assert(Math.Min(dstLo._s, dstUp._s) <= isect._s);
Debug.Assert(isect._s <= Math.Max(orgLo._s, orgUp._s));
if (Geom.VertLeq(isect, _event))
{
// The intersection point lies slightly to the left of the sweep line,
// so move it until it's slightly to the right of the sweep line.
// (If we had perfect numerical precision, this would never happen
// in the first place). The easiest and safest thing to do is
// replace the intersection by tess._event.
isect._s = _event._s;
isect._t = _event._t;
}
// Similarly, if the computed intersection lies to the right of the
// rightmost origin (which should rarely happen), it can cause
// unbelievable inefficiency on sufficiently degenerate inputs.
// (If you have the test program, try running test54.d with the
// "X zoom" option turned on).
MeshUtils.Vertex orgMin = Geom.VertLeq(orgUp, orgLo) ? orgUp : orgLo;
if (Geom.VertLeq(orgMin, isect))
{
isect._s = orgMin._s;
isect._t = orgMin._t;
}
if (Geom.VertEq(isect, orgUp) || Geom.VertEq(isect, orgLo))
{
// Easy case -- intersection at one of the right endpoints
CheckForRightSplice(regUp);
_pool.Return(isect);
return(false);
}
if (!Geom.VertEq(dstUp, _event) &&
Geom.EdgeSign(dstUp, _event, isect) >= 0.0f ||
!Geom.VertEq(dstLo, _event) &&
Geom.EdgeSign(dstLo, _event, isect) <= 0.0f)
{
// Very unusual -- the new upper or lower edge would pass on the
// wrong side of the sweep event, or through it. This can happen
// due to very small numerical errors in the intersection calculation.
if (dstLo == _event)
{
// Splice dstLo into eUp, and process the new region(s)
_mesh.SplitEdge(_pool, eUp._Sym);
Mesh.Splice(_pool, eLo._Sym, eUp);
regUp = TopLeftRegion(regUp);
eUp = RegionBelow(regUp)._eUp;
FinishLeftRegions(RegionBelow(regUp), regLo);
AddRightEdges(regUp, eUp._Oprev, eUp, eUp, true);
_pool.Return(isect);
return(true);
}
if (dstUp == _event)
{
/* Splice dstUp into eLo, and process the new region(s) */
_mesh.SplitEdge(_pool, eLo._Sym);
Mesh.Splice(_pool, eUp._Lnext, eLo._Oprev);
regLo = regUp;
regUp = TopRightRegion(regUp);
MeshUtils.Edge e = RegionBelow(regUp)._eUp._Rprev;
regLo._eUp = eLo._Oprev;
eLo = FinishLeftRegions(regLo, null);
AddRightEdges(regUp, eLo._Onext, eUp._Rprev, e, true);
_pool.Return(isect);
return(true);
}
// Special case: called from ConnectRightVertex. If either
// edge passes on the wrong side of tess._event, split it
// (and wait for ConnectRightVertex to splice it appropriately).
if (Geom.EdgeSign(dstUp, _event, isect) >= 0.0f)
{
RegionAbove(regUp)._dirty = regUp._dirty = true;
_mesh.SplitEdge(_pool, eUp._Sym);
eUp._Org._s = _event._s;
eUp._Org._t = _event._t;
}
if (Geom.EdgeSign(dstLo, _event, isect) <= 0.0f)
{
regUp._dirty = regLo._dirty = true;
_mesh.SplitEdge(_pool, eLo._Sym);
eLo._Org._s = _event._s;
eLo._Org._t = _event._t;
}
// leave the rest for ConnectRightVertex
_pool.Return(isect);
return(false);
}
// General case -- split both edges, splice into new vertex.
// When we do the splice operation, the order of the arguments is
// arbitrary as far as correctness goes. However, when the operation
// creates a new face, the work done is proportional to the size of
// the new face. We expect the faces in the processed part of
// the mesh (ie. eUp._Lface) to be smaller than the faces in the
// unprocessed original contours (which will be eLo._Oprev._Lface).
_mesh.SplitEdge(_pool, eUp._Sym);
_mesh.SplitEdge(_pool, eLo._Sym);
Mesh.Splice(_pool, eLo._Oprev, eUp);
eUp._Org._s = isect._s;
eUp._Org._t = isect._t;
_pool.Return(isect);
isect = null;
eUp._Org._pqHandle = _pq.Insert(eUp._Org);
if (eUp._Org._pqHandle._handle == PQHandle.Invalid)
{
throw new InvalidOperationException("PQHandle should not be invalid");
}
GetIntersectData(eUp._Org, orgUp, dstUp, orgLo, dstLo);
RegionAbove(regUp)._dirty = regUp._dirty = regLo._dirty = true;
return(false);
}
