BSP-Quake IIII integrated BSP into my 3d engine including the ability to load Quake 3 map files. Entire Quake 3 maps could be rendered complete with built-in textures and light maps. Frustum and occlusion culling were performed on the BSP to greatly reduce the poly-count per frame. My engine also supported ray casting on a per-face then per-poly basis while using the BSP to perform in-order search based on distance.

This video demos the Ray-Tracing.  The engine casts a ray forward from the camera into the world and places the small, purple ball wherever that ray strikes the environment.

Video Demo of Ray Tracing

Here are several more examples of my engine running: