raytracer: add support for per-point pointsize

[carli2]

I created this patch to support pixel-perfect collision detection with individually sized points.

Here's an example vertex shader to use gl_Points with pointsize in world-coordinates:

      attribute float pointsize;
      uniform vec2 resolution;
      void main() {
         gl_Position = projectionMatrix * modelViewMatrix * vec4(position.x, position.y, position.z, 1.0);
         gl_PointSize = pointsize * resolution.y * projectionMatrix[1][1] / gl_Position.w;
      }

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	687.32 170.19	687.52 170.25	+202 B +55 B
WebGPU	836.34 224.18	836.54 224.24	+202 B +55 B
WebGPU Nodes	835.85 224.06	836.05 224.12	+202 B +59 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	463.24 111.86	463.24 111.86	+0 B +0 B
WebGPU	532.75 143.69	532.75 143.69	+0 B +0 B
WebGPU Nodes	489.1 133.44	489.1 133.44	+0 B +0 B