This is an example of creating a Menger Sponge in pbrt-v4 by abusing the Import/Include directives.
The scene contains a Menger Sponge of 10 iterations, 10,240,000,000,000 boxes, and is constructed using a combination of ObjectInstances and nested Includes. To get to the 10 iterations we use-
- 4 iterations - PlyMesh geometry that is ~1,920,000 triangles.
- 1 iteration - Placing the PlyMesh 20 times
- 5 iterations - Utilizing the iterative nature of the Menger Sponge we can repeatedly apply the same set of transforms, nesting Includes as we go.
This gives us our 10 iterations and will require roughly 3GB to 4GB of VRAM to render on the GPU.
If you happen to have over 15GB GB of VRAM on your GPU you can edit the scene.pbrt and use
Include "./instancing/instancer_6.pbrt"
This will give you 11 iterations, or 204,800,000,000,000 boxes.
When using the instancer_6.pbrt, it uses Imports instead of Includes which allows the nested structures to be built across 20 different threads greatly speeding up the load time. On my machine when rendering instancer_6.pbrt the time to first pixel is about 50s.
Try it out in interactive mode!
pbrt --interactive --gpu scene.pbrt