Wavefront mesh: determine which face a point belongs to?

Question

I have a 3D mesh Wavefront .obj file.

Is there any algorithm that takes an arbitrary point coordinates as input and determines which face of the mesh that point belongs to ??

The mesh is rendered on the screen, then the user clicks on it, I want to determine which part of the mesh the user has clicked on ?

Here's the code using LibGDX:

Vector3 intersection=new Vector3();
Ray ray=camera.getPickRay(x, y);
//vertices is an array that hold the coordinates of the mesh
boolean ok=Intersector.intersectRayTriangles(ray, vertices, intersection);

Thanks

Answer 1

For each face in the mesh: test for a ray-triangle intersection using a ray that goes through the pixel the user clicked on.

You can compute the ray using gluUnproject (or the equivalent math). Unproject two points with winX and winY set to where the user clicked: one with winZ=0.0 at the near plane, and one with winZ=1.0 at the far plane. These two points form a line you can use to test for triangle intersections.