Noticed an unusual interaction with Virtual Shadow Maps when combined with Variable Rate Shading and WPO materials.
The coarser the shading rate, the less visible the shadow becomes - but only when the object is effected by a WPO (foliage with wind in my case).
1x1 shading rate results in a typical full shadow.
1x2/2x1 reduce shadows to about 75% darkness.
2x2 reduces shadows to 50% darkness.
2x4/4x2 reduce shadows to 25% darkness.
4x4 makes shadows completely invisible.
If I disable the WPO, shadows are restored fully. If I disable VRS, shadows are restored fully.
Standard Cascading Shadow Maps and Ray Traced Shadows do not exhibit this behavior.
This discovery was a bummer because I found surprisingly little loss in visual quality when using even very aggressive VRS on certain foliage meshes.
Edit: The same issue occurs with masked materials, even with WPO off. So other similar interactions may exist.
Originally I was testing with opaque foliage and relying on the leaf geometry to preserve the mesh silhouette. VRS doesn’t look great on masked materials because it downscales the opacity mask which fails to maintain detail on the cards used with some LODs (although not as bad as you might expect).