Mike Zimmerman created MATH-1211:
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Summary: PolyhedronsSet.firstIntersection(Vector3D point, Line
line) sometimes reports intersections on wrong end of line
Key: MATH-1211
URL: https://issues.apache.org/jira/browse/MATH-1211
Project: Commons Math
Issue Type: Bug
Reporter: Mike Zimmerman
I constructed a PolyhedronsSet from a list of triangular faces representing an
icosphere (using the instructions found at
https://mail-archives.apache.org/mod_mbox/commons-user/201208.mbox/<[email protected]>).
This seems to produce correct INSIDE/OUTSIDE results for randomly chosen
points. I think my mesh triangles are defined appropriately.
However, using PolyhedronsSet.firstIntersection(Vector3D point, Line line) to
shoot randomly oriented rays from the origin sometimes gives a wrong mesh
intersection point "behind" the origin. The intersection algorithm is
sometimes picking up faces of the sphere-shaped mesh on the wrong semi-infinite
portion of the line, i.e.
meshIntersectionPoint.subtract(point).dotProduct(line.getDirection())<0 where
point is the Vector3D at center of the sphere and line extends outward through
the mesh.
I think the dot product above should always be positive. If multiple
intersections exist along a "whole" line then the first one in "front" of the
line's origin should be returned. This makes ray tracing with a PolyhedronsSet
possible.
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