Overhaul of directional PCSS shadows

[mvaligursky]

New implementation of PCSS for directional light:

• visually much more pleasing compared to the existing implementation
• option to skip the shadow blocker for larger constant size PCF shadow
• variable number of samples for both blockers as well as shadow filtering

New public API

// control of the contact hardening rate
LightComponent.penumbraFalloff   // in addition to existing penumbraSize

// cost vs quality controls
LightComponent.shadowSamples   // number of samples of PCF filter, range 1 - ∞
LightComponent.shadowBlockerSamples // number of samples to determine contact hardening, 0 - ∞.
// 0 disables contact hardening and constant penumbraSize is used

GPU Performance at 4K on Apple M1 Pro:
PCF3: 5.0ms
PCSS: 6.3ms // basic quality: blocker samples 8, PCF samples 12
PCSS: 9.1ms // high quality: blocker samples 28, PCF samples 42
PCSS: 6.7ms // medium quality, no contact hardening: blocker samples 0, PCF samples 16
PCSS: 9.7ms // extreme quality: blocker samples 32, PCF samples 64

PCF3

PCSS basic

PCSS high

PCSS no contact hardening

PCSS extreme

[willeastcott]

I notice that when a cloud's shadow passes over a tree's shadow, the tree's shadow kinda looks like it's overwritten rather than the cloud's shadow only darkening the terrain. Is there any way around that?

[mvaligursky]

I notice that when a cloud's shadow passes over a tree's shadow, the tree's shadow kinda looks like it's overwritten rather than the cloud's shadow only darkening the terrain. Is there any way around that?

Not using PCSS, similarly to VSM, it does not correctly handle overlapping casters at various distances.
Raytraced shadow is a solution.

[willeastcott]

Very cool.