Further reading
The book Real-Time Shadows provides a good overview of many techniques to implement shadows, many of which are still in use today.
GPU Pro 360 Guide to Shadows collects articles from the GPU Pro series that are focused on shadows.
An interesting technique described in the book is called tetrahedron shadow mapping: the idea is to project the shadow map to a tetrahedron and then unwrap it to a single texture.
The original concept was introduced in the Shadow Mapping for Omnidirectional Light Using Tetrahedron Mapping chapter (originally published in GPU Pro) and later expanded in Tile-based Omnidirectional Shadows (originally published in GPU Pro 6).
For more details, we refer you to the code provided by the author: http://www.hd-prg.com/tileBasedShadows.html.
Our sparse texture implementation is based on this SIGGRAPH presentation: https://efficientshading.com/wp-content/uploads/s2015_shadows.pdf.
This expands on their original paper, found here: http...
