Houdini Cube Maps

There are a few built-in ways to generate environment maps in Houdini - they can be auto-generated by each object, and you'll need to use the isixpack command line tool to combine them, or render a polar environment map with a camera and use hdrshop to convert to whatever format you need. The isixpack workflow is a tiny bit annoying and I wondered if it could be possible to generate a map like this at a go directly without isixpack. Also, I don't run windows, so HDRshop is out of the question for me.

Came up with this idea of using Mantra's UV space rendering to render a cube with its UVs laid out in the vertical cross format. And the shader simply shot a ray into space (the direction vector is simply current object space position, as my cube was at the origin). Good fun. Now to do something more productive, like figure out bullet constraints in-depth.