WebGPURenderer: PCF shadow filtering with Vogel disk sampling and IGN.

[mrdoob]

Related issue: #32303

Description

Ports the modernized PCF shadow filtering from WebGLRenderer to WebGPURenderer.

Changes

• Replace 17-sample grid pattern in PCFShadowFilter with 5-sample Vogel disk distribution
• Replace 9-sample axis-aligned pattern in PointShadowFilter with 5-sample Vogel disk in tangent space
• Use Interleaved Gradient Noise (IGN) to rotate sampling pattern per-pixel, eliminating banding artifacts
• Add vogelDiskSample TSL function to PostProcessingUtils.js

Benefits

• Fewer texture samples (5 vs 17/9) with better quality due to optimal disk distribution
• Combined with hardware PCF (4-tap filtering), effectively 20 filtered taps per pixel
• Per-pixel IGN rotation breaks up shadow edge banding

(Made using Claude Code with Opus 4.5)

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	350.29 83.05	350.29 83.05	+0 B +0 B
WebGPU	613.1 170.13	613.24 170.24	+141 B +117 B
WebGPU Nodes	611.7 169.85	611.84 169.96	+141 B +112 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	482.23 117.82	482.23 117.82	+0 B +0 B
WebGPU	684.25 185.94	684.39 186.07	+131 B +125 B
WebGPU Nodes	634.08 173.15	634.21 173.25	+131 B +107 B