Sat, 06/06/2015 - 18:22
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I need to obtain normals at the intersection vertices between my voxel discretization and surface. What is the easiest way to obtain such normals, and intersection points.
Collaborative development portal
Mon, 06/08/2015 - 11:32
For intersection points between curves and surfaces you might want to check GeomAPI_ExtremaCurveSurface.
A surface normal at a certain point can be obtained like this: project the point onto the surface to get its u and v parameter. For this you could use ShapeAnalysis_Surface::ValueOfUV. Then compute the first derivatives of the surface to have vectors spanning the tangent space. This can be done with Geom_Surface::D1. If you compute the cross product of both vectors, you have the normal vector.
Benjamin
Mon, 06/08/2015 - 16:10
Hi Benjamin,
Thank you for your answer, I understood the second part, but could you elaborate a bit on first part. I have voxelised surface, and then I need to find the intersection points for every voxel.
Stefan
Mon, 06/08/2015 - 18:18
I am sorry, my proposal only works if you have a Geom_Surface or something similar.
Benjamin
Mon, 06/08/2015 - 18:48
Anyway thanks for the effort