Add PBR rendering pipeline: GGX BRDF, Fresnel, tone mapping, environment sky#26
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…ent sky Upgrade miniRT toward an offline renderer with physically-based rendering: - PBR materials: metallic-roughness workflow with GGX/Cook-Torrance BRDF and Schlick Fresnel approximation (ft_pbr.c) - New material properties: metal:, rough:, emit: parsed from .rt files - ACES filmic tone mapping replaces simple gamma for HDR support (ft_argb.c) - Environment sky lighting with gradient hemisphere (ft_env.c) - Path tracer upgraded with Russian Roulette termination, emissive materials, and PBR-aware direct lighting - PBR shading integrated into interactive Phong renderer (ft_light.c) - PBR showcase scene (scenes/pbr_showcase.rt) All 174 tests pass (452 assertions, 0 failures). https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
… tool - Fix clang-format issues in ft_light.c, ft_pathtrace.c, ft_pbr.c - Regenerate all 19 regression reference BMPs for ACES tone mapping - Add renders_preview/ with PNG versions of all renders for PR review - Add tools/bmp_to_png.py script to automate BMP->PNG conversion https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
Two issues caused existing scenes to lose colors and lighting: 1. Default roughness was 0.5, which activated PBR shading on ALL shapes even without explicit PBR properties. Fixed: default roughness = 0.0, so PBR is opt-in only (via metal:/rough: in .rt files). 2. ACES tone mapping was applied to all renders, compressing the standard Phong pipeline's [0,255] output. Fixed: ACES only activates for path tracing (HDR); standard rendering keeps the original gamma correction. All 19 regression references are now pixel-identical to the pre-PBR originals. https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
- Fix upside-down renders: remove rot_z=-1 (180° roll) from new_shapes.rt and pbr_showcase.rt camera orientations - Add 'E' scene directive to enable environment sky gradient background (opt-in, existing scenes unchanged) - Standard renderer returns sky color for ray misses when E is set - Redesign new_shapes.rt: camera at elevated position looking down, objects well-spaced, two lights, sky background - Redesign pbr_showcase.rt: 3 rows (dielectric, metallic, mixed shapes), elevated overview camera, sky background, 1920x1080 18 unchanged regression scenes remain pixel-identical to originals. https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
New test file tests/test_pbr.c with 25 tests (76 assertions) covering: - ft_fresnel_schlick: head-on, grazing, 45deg, negative clamp, metal - ft_env_sky: zenith, horizon, down, below-clamp directions - ft_material_default: all 13 field defaults including new PBR fields - ft_reflect_ray: straight-on and 45-degree reflection - ft_refract_ray: normal incidence and total internal reflection - ft_parse_material: metal:, rough:, emit:, combined, vel: keywords - ft_pbr_shade: head-on dielectric, backface, metallic - ft_light PBR branch: metallic/roughness triggers PBR path - ft_trace_ray_recursive: env sky miss vs black miss Coverage: 53.1% lines (1451/2735), 62.5% functions (150/240) Total test suite: 199 tests, 528 assertions, 0 failures https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
New scene: - scenes/materials.rt: showcases ALL material properties in 3 rows: row 1 (spec, refl, trans+ior glass, trans+ior diamond), row 2 (PBR metal chrome/brushed/rough, glossy plastic), row 3 (emissive box, metallic+reflective cylinder, transparent cone) Fix post-42 scenes to follow guidelines (elevated camera, sky background): - quadrics.rt: remove rot_z=-1, add E, elevated camera - new_shapes.rt: remove rot_z=-1, add E, elevated camera - benchmark.rt: remove rot_z=1, add E, elevated camera at z=60 - dof_test.rt: add E for sky background - motion_blur.rt: add E for sky background - taurus.rt: add E for sky background - cathedral_ruins.rt: add E for sky background Original 42 project scenes (cylinder, exemple, inside_*, lights, objects, square, tiny, triangle, error) left unchanged. https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
Re-rendered saves/ for scenes with camera/sky fixes: - new_shapes, quadrics, taurus (camera rot_z fix + E directive) - benchmark (camera fix + E directive) New saves/ for scenes that were missing: - materials, pbr_showcase, dof_test, motion_blur, benchmark Updated renders_preview/ PNGs from all 20 saves/ + 19 regression refs. Cathedral render in progress (~1h at 2560x1440), will update separately. https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
Scene fixes: - quadrics.rt: spread objects wider (x=-8 to 8), camera higher (y=14) and further (z=24), pitch 0.15 for proper overhead view - new_shapes.rt: spread objects wider (x=-12 to 12, 2 z-planes), camera at (0,14,28) with pitch 0.15 Documentation: - skills/camera-and-rendering.md: add "Post-42 Scene Generation Rules" section with drone-view camera formula, sky background, object layout, and PBR material properties table - CLAUDE.md: add "Development Workflow" section requiring lint/test/ regression on every iteration, saves/ and renders_preview/ updates when scenes change Updated saves/ and renders_preview/ for both changed scenes. Lint OK, 199 tests pass, 19/19 regression pass. https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f
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Upgrade miniRT toward an offline renderer with physically-based rendering:
and Schlick Fresnel approximation (ft_pbr.c)
and PBR-aware direct lighting
All 174 tests pass (452 assertions, 0 failures).
https://claude.ai/code/session_011AkHu1jxvYRN9F9pGfuF7f