On Wed, 11 Mar 2015, Roy Stogner wrote: > On Wed, 11 Mar 2015, David Knezevic wrote: > >> On Wed, Mar 11, 2015 at 12:29 PM, Roy Stogner <royst...@ices.utexas.edu> >> wrote: >> >> We need some kind of fully general intersection test for cartesian >> boxes with libMesh elements... > >> Hmm, OK. Do you have an idea about how to implement that? I'll be happy to >> help out, if needed. > > No great ideas. I've only seen intersection tests for cases involving > polyhedra, spheres, and cones, not arbitrary quadratic parametric > volumes. > > We could probably handle the (tri,bi,)linear non-axis-aligned > anisotropic cases with standard algorithms, though: orthogonalize the > vectors given by dx/dxi to get a more appropriate coordinate system, > find the "axis-aligned bounding box" by translating the nodes into > those coordinates, and do the intersection test for that bounding box > with the coordinate-aligned BB that our trees use. The trilinear case > has curved faces, but I believe each face is still always bounded by > any bounding box of its four nodes. > > http://www.realtimerendering.com/intersections.html > > We'll need to figure out something smarter before we get to play > safely with point locators for general quadratic geometry or NURBS, > though.
To clarify: although an exact intersection test would be *great*, all we need for now is something like the above: a test that doesn't give us any false negatives or *too* many false positives. --- Roy ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Libmesh-devel mailing list Libmesh-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-devel
