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Triangle search algorithm #34
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So as you mentioned inserting vertices in constrained triangulation is not supported. But there is also another reason for that: when inserting vertices edges are flipped to ensure Delaunay property. And the algorithm does not currently handle constraints at this point. |
Alright, wasn't sure that your implementation is for offline use only so decided to point out potential issue. I have halfe edge delaunay triangulation implementation that can perform operations in runtime and had to deal with that kind of issues. |
Please disregard my previous message. Here's the code template <typename T>
TriInd Triangulation<T>::walkTriangles(
const VertInd startVertex,
const V2d<T>& pos) const
{
// begin walk in search of triangle at pos
TriInd currTri = vertices[startVertex].triangles[0];
#ifdef CDT_USE_BOOST
TriIndFlatUSet visited;
#else
TriIndUSet visited;
#endif
bool found = false;
while(!found)
{
const Triangle& t = triangles[currTri];
found = true;
// stochastic offset to randomize which edge we check first
const Index offset(detail::randGen() % 3);
for(Index i_(0); i_ < Index(3); ++i_)
{
const Index i((i_ + offset) % 3);
const V2d<T> vStart = vertices[t.vertices[i]].pos;
const V2d<T> vEnd = vertices[t.vertices[ccw(i)]].pos;
const PtLineLocation::Enum edgeCheck =
locatePointLine(pos, vStart, vEnd);
if(edgeCheck == PtLineLocation::Right &&
t.neighbors[i] != noNeighbor &&
visited.insert(t.neighbors[i]).second)
{
found = false;
currTri = t.neighbors[i];
break;
}
}
}
return currTri;
} Flipping a fixed edge could still be a problem. How does your implementation handle this? |
I track what edges are constrained. Constrained edges are not getting flipped. You can play with Spine. They use CDT to interactively create meshes. |
Thanks. If it's just this single check then it should be really easy to add. |
When vertices are inserted into a triangulation that already has some constraints (fixed edges): fixed edges should not be flipped.
When vertices are inserted into a triangulation that already has some constraints (fixed edges): fixed edges should not be flipped.
#44 |
Your search algorithm (crossing the dividing edge) requires triangulation to be delaunay (not constrained delaunay). But you can use stochastic walk instead of using data structure to store visitted.
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