Fix pbr_demo, multi_light_demo, and shadow_demo to use the new 7-param
create_pbr_pipeline with PBR texture bind group (4-entry: albedo+normal)
and IBL bind group. Create ibl_demo showcasing a 7x7 metallic/roughness
sphere grid with IBL-based ambient lighting via BRDF LUT integration.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- 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>
