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Posted to issues@commons.apache.org by "Luc Maisonobe (JIRA)" <ji...@apache.org> on 2015/04/09 22:38:12 UTC
[jira] [Resolved] (MATH-1211)
PolyhedronsSet.firstIntersection(Vector3D point, Line line) sometimes
reports intersections on wrong end of line
[ https://issues.apache.org/jira/browse/MATH-1211?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Luc Maisonobe resolved MATH-1211.
---------------------------------
Resolution: Fixed
Fix Version/s: 3.5
Your analysis was perfectly correct and your solution was good. I only made
a minor change so it is easier to understand.
Fixed in git repository. Beware the fix is currently only in the MATH_3_X branch, which is not the master branch. It will be included in the upcoming 3.5 release.
Thanks for the report and the fix.
> 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
> Fix For: 3.5
>
> Attachments: IntersectionTest.java
>
>
> 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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