- Add Mat4::orthographic() to voltex_math for light projection
- Fix pbr_demo and multi_light_demo to provide shadow bind group (group 3)
required by updated PBR pipeline (dummy shadow with size=0 disables it)
- Create shadow_demo with two-pass rendering: shadow depth pass using
orthographic light projection, then PBR color pass with shadow sampling
- Scene: ground plane, 3 spheres, 2 cubes with directional light
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Fix pbr_demo to use LightsUniform/LightData instead of old LightUniform.
Create multi_light_demo with 5 PBR spheres (varying metallic), a ground
plane, 4 colored orbiting point lights, a directional fill light, and a
spot light from above.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
7x7 grid of spheres demonstrating PBR material variation:
metallic increases along X axis, roughness along Y axis.
Uses dynamic UBO pattern for both camera and material uniforms.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Previous approach called write_buffer inside render pass which doesn't
work — GPU only sees the last value at submit time. Now pre-computes all
entity uniforms into a dynamic UBO and uses dynamic offsets per draw call.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
