Implement PoissonBlurMaterial

Description

Implement a PoissonBlurMaterial.

References:

• https://github.com/0beqz/realism-effects/tree/061daeaefb7773d8a1a8e10fa95a184fbcda1fb7/src/denoise
• https://github.com/N8python/n8ao/blob/8a79a026eab3899990322596e893d1fbd9ba3f89/src/PoissionBlur.js
• https://github.com/gkjohnson/threejs-sandbox/blob/8ebf61b0a36d188ccf50f31d31dacc44319e3986/blue-noise-generation/src/BlueNoiseGenerator.js
• https://github.com/0beqz/realism-effects/tree/061daeaefb7773d8a1a8e10fa95a184fbcda1fb7/src/utils
• https://diharaw.github.io/post/adventures_in_hybrid_rendering/

Tasks

• Create PoissonKernel util (see GaussKernel).
• Create BlueNoiseTexture util.
• Create PoissonBlurMaterial.
• Add unit test.

Implementation Details

• The blur shader must support bilateral convolution (depth and normals).
• Depth and normals are separate input textures.
  • Consider adding support for a combined normal-depth input texture (normal-depth downsampling).
• The blur kernel should use a Poisson disc distribution.
• The shader should support rotating the sampling disc using blue noise.

Start by reviewing the existing GaussKernel utility and the referenced PoissionBlur.js, BlueNoiseGenerator.js, and realism-effects denoise and utils implementations. Create the PoissonKernel, BlueNoiseTexture, and PoissonBlurMaterial, then add the requested unit test. Done means the shader supports Poisson-disc sampling, blue-noise rotation, and bilateral depth and normal convolution.