I first learned of Variance Shadow Mapping technique from the GPU Gems 3 article back when I was an undergrad. At the time I thought it was a pretty neat way of generating shadows that produced some nice results. The part that I didn't quite understand at the time was how to generate summed-area shadow textures and use them to produce soft shadows. Now that I have more experience with graphics API under my belt, I decided to revisit this topic and to implement Summed-Area Soft Variance Shadows in all of their natural glory.
- Deferred shading with Real-Time soft variance shadow utilizing summed-area table.
- Summed-area textures can be generated using compute shader or using Hensley's recursive doubling method.
- Percentage-Closer Soft Shadows are implemented as was described in Fernando's 2005 paper.
- Run-time debugging of shadow map and light configuration thru the utilization of Dear ImGui library.
- Don’t go above 1K for the size of your SATs or your shadow will fail!
- Summed-Area Tables will greatly magnify all the problems that filtered shadow techniques have.
- Filtering using SATs is fast and very good quality, but works much better for larger kernel sizes.
- Floating-point precision caused a lot of issues.
Copyright (C) 2021 Roman Timurson
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