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Signed Distance Functions are a pretty simple concept. Basically for each point in the world, you return a distance to the nearest surface, negative distances are inside geometry. One neat application of them to represent scene geometry, and ray trace into the SDF. Why would anyone do such a thing? Well, it turns out that when marching along a ray looking for intersections (which is obviously not the only way to trace rays), it’s jolly useful to know a minimum bound on when you might expect to encounter a surface. This way you can keep taking large jumps along the ray, using the SDF to figure out how large, until you finally reach some threshold distance. Here’s the end result of the code I’m presenting in this blog post.