corkum@csri.toronto.edu (Brent Thomas Corkum) (04/12/91)
I'm looking for a reference, algorithm or C code snipit that calculates the EXACT distance from a 3D point to 3D CONVEX polygon (always a triangle or quadralateral). In the end though, I need to calculate the distance from a point to a closed CONCAVE or CONVEX object made up of these polygons. The way I would do it now is to test 2 cases for each polygon, 1) calculate the normal distance to the polygon plane and the intersection point on the plane. If the intersection point is within the bounds of the polygon use this distance, else go to step 2. 2) Calculate the distance to each of the edge lines of the polygon. Since my object is closed and my test points are all outside my object I would also filter out backfacing polygons first. (I think this would work anyways!) This must be a common problem in computer graphics with lots of efficient algorithms for solution although I've looked in a variety of texts with little success. Brent Corkum corkum@boulder.civ.toronto.edu
sow@cad.luth.se (Sven-Ove Westberg) (04/13/91)
In article <1991Apr12.000218.3215@jarvis.csri.toronto.edu> corkum@csri.toronto.edu (Brent Thomas Corkum) writes: |I'm looking for a reference, algorithm or C code snipit that calculates |the EXACT distance from a 3D point to 3D CONVEX polygon (always a triangle or |quadralateral). In the end though, I need to calculate the distance from You can not calulate the EXACT distance to a quadralateral if it is not planar. On non planar quadralateral the distance depends on how you define the surface. One common way do do it is to divide each quadralateral in two triangels. You can divide the quadralateral in two ways and get different results. Sven-Ove Westberg, CAD, University of Lulea, S-951 87 Lulea, Sweden. Internet: sow@cad.luth.se