Expose GSplat rendering properties on GSplatParams

[mvaligursky]

Adds configurable rendering properties to GSplatParams (app.scene.gsplat) for unified mode, and replaces the hardcoded 2-pixel splat size cutoff with a configurable uniform. Fixes #8437.

Changes:

• Replace hardcoded 2-pixel splat cutoff in vertex shader with configurable minPixelSize uniform (GLSL + WGSL)
• Add alphaClip, minPixelSize, antiAlias, and twoDimensional properties to GSplatParams
• Set minPixelSize default (2.0) on non-unified material for backward compatibility
• Remove redundant alphaClip default from GSplatRenderer (now flows from GSplatParams)

API Changes:

• app.scene.gsplat.alphaClip (number, default 0.3) — alpha threshold for shadow/pick/prepass passes
• app.scene.gsplat.minPixelSize (number, default 2) — minimum screen-space pixel size before splats are culled
• app.scene.gsplat.antiAlias (boolean, default false) — enables anti-aliasing compensation
• app.scene.gsplat.twoDimensional (boolean, default false) — enables 2D Gaussian Splatting mode

Examples:

• Added minPixelSize slider to LOD streaming example
• Added alphaClip slider to shadows example (new controls file)
• Updated flipbook and shadows examples to use new alphaClip API

[Copilot]

Pull request overview

This PR exposes several GSplat rendering controls via GSplatParams (app.scene.gsplat) for unified Gaussian Splatting, including making the “2px cutoff” culling threshold configurable via a new minPixelSize uniform (GLSL + WGSL), and updates examples to use the new API.

Changes:

• Replace hardcoded “< 2px” splat early-out in GSplat corner vertex code with a configurable minPixelSize uniform (GLSL/WGSL).
• Add alphaClip, minPixelSize, antiAlias, and twoDimensional properties to GSplatParams and align unified renderer defaults with those params.
• Update examples (and add new shadows controls) to drive GSplat settings through app.scene.gsplat.*.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/scene/shader-lib/wgsl/chunks/gsplat/vert/gsplatCorner.js	Adds minPixelSize uniform and uses it for small-splat early-out in WGSL.
src/scene/shader-lib/glsl/chunks/gsplat/vert/gsplatCorner.js	Same minPixelSize uniform + early-out change for GLSL.
src/scene/gsplat/gsplat-instance.js	Sets minPixelSize default (2.0) on non-unified materials for backward compatibility.
src/scene/gsplat-unified/gsplat-renderer.js	Removes redundant unified renderer alphaClip default (now sourced from params).
src/scene/gsplat-unified/gsplat-params.js	Introduces new GSplatParams properties and initializes defaults on the template material.
examples/src/examples/gaussian-splatting/shadows.example.mjs	Switches example to use observer-driven app.scene.gsplat.alphaClip.
examples/src/examples/gaussian-splatting/shadows.controls.mjs	New UI slider for alpha clip in the shadows example.
examples/src/examples/gaussian-splatting/lod-streaming.example.mjs	Adds observer binding to control app.scene.gsplat.minPixelSize.
examples/src/examples/gaussian-splatting/lod-streaming.controls.mjs	Adds UI slider for min pixel size.
examples/src/examples/gaussian-splatting/flipbook.example.mjs	Updates example to use app.scene.gsplat.alphaClip API.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.