Monthly Archives: August 2011

tsearchn and pointLocation

To use pointLocation() to find the enclosing simplex (triangle/tetrahedron) for each query point location in Matlab, one has to supply this function with a ‘DelaunayTri’ structure as an input. This is a newly introduced class for performing delaunay triangulation. While in my case I need to reuse my saved delaunay triangulation results and assigned it to the Triangulation component of the ‘DelaunayTri’ structure. However I got this error,

??? Error using ==> subsasgn
Cannot assign values to the Triangulation.

I think this is because Triangulation is a private member of the class DelaunayTri, and every time one revises the values of X, this Triangulation  is updated automatically. If you are still allowed, you can use the old function ‘tsearchn’ to find the enclosing simplex of the delaunay triangulation. It is also very easy to write a simple function to compute the barycentric coordinate for each query point location. In case ‘tsearchn’ is not supported by the future Matlab, you can also write your own version of ‘tsearchn’. The brute force way is to check the barycentric coordinate of that point for each triangle. If one of the coordinates is negative, then the point is outside of that triangle.