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https://issues.apache.org/jira/browse/MATH-1211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484866#comment-14484866
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Luc Maisonobe commented on MATH-1211:
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Hi Mike,
Could you attach a self-contained test to reproduce the error?
> 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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