CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 01/09/2018 10:29 AM, Maarten Moesen wrote:
> Dear CGAL community,
>
> First of all my best wishes for 2018 to the CGAL team and community!
>
> Question 1:
> In the AABB tree package there is plenty of support for (closest) 
> ray-triangle intersections which (very precisely) return a point or a 
> line segment. It could be, however, somewhat more convenient for my code 
> to work directly with the ray's intersection distance parameter (t). In 
> the documentation I've found a AABBRayIntersectionTraits Concept that 
> describes this. Is it meant to be used directly and if so, is there also 
> a model/example that shows how to?

This is something that must be provided to the algorithm so that it can
compute the closest intersected primitive.
There is no API to get the t value of the first primitive intersected.
The variable t is local to the function ray_intersection in there:
https://github.com/CGAL/cgal/blob/master/AABB_tree/include/CGAL/internal/AABB_tree/AABB_ray_intersection.h

> Question 2:
> I'm also interested in the texture coordinates (often denoted with 
> (t,u,v)) of the intersection of a ray with a triangle. Would this be 
> possible to obtain them directly or is it better to back-project the 
> point of intersection on the triangle?
I don't think we have something better than computing the intersection 
point inside the triangle and then get its barycentric coordinates.

Sebastien.


> Best regards,
>
> Maarten
> --
> Maarten Moesen, PHD
> Polymer Physicist Computational Modeling
>
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