[jira] [Created] (MATH-1211) PolyhedronsSet.firstIntersection(Vector3D point, Line line) sometimes reports intersections on wrong end of line

["Mike Zimmerman (JIRA)" <ji...@apache.org>]

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/<50...@free.fr>).  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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