Continuing from my deferred renderer project, I expanded framework to include support for filterable shadow maps using the Moment Shadow Mapping method. I was already familiar with the technique behind the Variance Shadow Maps by experimenting with them many years ago, so I was excited to see how this novel MSM technique provides "substantially higher quality" shadows, as the paper claims. Needless to say, I was somewhat disappointed but still glad that I got the opportunity to try it out for myself.
- Deferred shading with Real-Time soft shadows utilizing the Moment Shadow Map technique.
- Ability to change the shadow filtering kernel size dynamically. Supports 7x7, 15x15, 23x23, 35x25, and higher shadow filtering using "moving averages" box filter done in a compute shader.
- Run-time debugging of shadow map and light configuration thru the utilization of Dear ImGui library.
- Using the Hamburger 4MSM algorithm indeed produces very nice soft shadows.
- As the paper suggested, I first tried using the bias value (0.00003) and didn't notice any obvious light-bleeding artifacts. I then moved the light source around and quickly ran into what the paper described as "slight quantization noise." Those artifacts were very noticeable. Increasing the bias value by a factor of 10 did eliminate this ugly quantization noise completely, but then the light-bleeding will become more obvious. So, basically, just like their predecessors (VSM and EVSM), the Moment Shadows suffer from similar precision issues and require having just the right biasing value to produce acceptable results. Not to mention doing more per pixel calculations and even utilizing up to 128 bits per texel, which is quite a bit of memory and bandwidth.
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