# OpenCL GPGPU Complex Raytracing

Contact "brlcad" on irc.freenode.net

BRL-CAD has one of the oldest and fastest parallel ray tracing implementations around but we don't currently leverage the GPU. With implicit geometry and constructive solid geometry (CSG) Boolean operations, we also have a very different approach to ray tracing that has its own set of academic challenges.

Your project is to help us introduce a GPGPU pipeline into BRL-CAD using OpenCL. You're welcome to use a library that encapsulates OpenCL. We have a dozen primitives in BRL-CAD that need to be converted to OpenCL. One of them which is done is an arbitrary polyhedron, so you have an example to follow. Your objective is to implement at least two more while evaluating how your conversion compares to the non-GPGPU implementation.

These complex primitives still need to be converted: pipe, displacement map, extruded bitmap (similar to displacement map), metaball, and 3-D volume (also similar to displacement map).

The bot (Bag Of Triangles) primitive i.e. triangle mesh also needs plate mode support. i.e. triangles with thickness. In addition the current intersection algorithm needs to be replaced with an algorithm which is watertight. This might either be the algorithm in the ANSI C backend or perhaps the one below.

- http://jcgt.org/published/0002/01/05/ - Watertight Ray/Triangle Intersection.

Difficulty: Medium

Languages: C and OpenCL (or other GPGPU API)