Primitive Intersections
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Currently XDG supports ray intersections with the following primitives:

   - linear triangles
   - linear quads

Triangle intersection tests are performed using the Pluecker triangle
intersection test. This method uses Pluecker coordinates (formed from the
cross-product of the ray direction and triangle edges) to determine if a ray
intersects a triangle. It is known for its numerical stability and efficiency,
making it suitable for scientific ray tracing applications [1]_.

Quad intersection tests are performed by splitting the quad into two triangles
and performing the Pluecker triangle intersection test on each triangle.

Assumptions about the normals of primitives are based the cannonical ordering
established by this paper [2]_.


.. [1] T. H. Havran, "Fast Ray-Tetrahedron Intersection Using Plucker Coordinates,"
       Journal of Graphics Tools, vol. 8, no. 1, pp. 25-32, 2003.
       http://dx.doi.org/10.1080/10867651.2003.10487593

.. [2] T. J. Tautges, "Canonical numbering systems for finite-element codes,"
       International Journal for Numerical Methods in Biomedical Engineering,
       vol. 26, no. 8, pp. 1033-1049, 2010. https://doi.org/10.1002/cnm.1237