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

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.5
• Assignee: Unassigned
• Reporter: Mike Zimmerman
• Created: 08/Apr/15 02:25
• Updated: 18/Apr/15 09:28
• Resolved: 09/Apr/15 20:37

Description

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/<[e-mail]>). 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.