Implement SSGIEffect

[vanruesc]

Description

Implement a SSGIEffect.

References:

• https://github.com/0beqz/realism-effects/tree/main/src/ssgi
• https://arxiv.org/pdf/2301.11376.pdf
• Postprocessing: Add SSILVB GI and AO mrdoob/three.js#29668

Tasks

• Create SSGIEffect.
• Create ssgi demo.
• Add unit test.

Implementation Details

• Use G-Buffer components (depth, normals, ORM).

[jo-chemla]

In case it's useful, threejs introduced TSL SSGINode to the WebGPURenderer: mrdoob/three.js#31839 and demo