Add PBR rendering pipeline: GGX BRDF, Fresnel, tone mapping, environment sky

CLAUDE.md

@@ -90,14 +90,16 @@ mini_rt/
 │   ├── ft_paraboloid.c      # Paraboloid intersection
 │   ├── ft_csg.c             # CSG operations (union, intersect, difference)
 │   ├── ft_mesh.c            # OBJ mesh loading
-│   ├── ft_material.c        # Material properties (refl, trans, spec, ior)
+│   ├── ft_material.c        # Material properties (refl, trans, spec, ior, PBR)
 │   ├── ft_texture.c         # Texture mapping
 │   ├── ft_bump.c            # Bump/normal mapping
 │   ├── ft_bvh.c / ft_bvh_2.c    # BVH acceleration structure
 │   ├── ft_threads.c         # Multi-threaded rendering
 │   ├── ft_dof.c             # Depth of field
 │   ├── ft_motion.c          # Motion blur
 │   ├── ft_pathtrace.c       # Path tracing / global illumination
+│   ├── ft_pbr.c             # PBR shading (GGX/Cook-Torrance BRDF, Fresnel)
+│   ├── ft_env.c             # Environment sky lighting
 │   ├── ft_precompute.c      # Shape precomputation / caching
 │   ├── ft_parsing.c / ft_parsing_2.c      # Scene file (.rt) parser
 │   ├── ft_check_parsing.c / ft_check_parsing_2.c  # Input validation
@@ -134,7 +136,7 @@ mini_rt/
 ├── libft/                   # Custom 42 utility library
 ├── mlx/                     # minilibX (macOS)
 ├── mlx_linux/               # minilibX (Linux)
-├── scenes/                  # 19 example .rt scene files
+├── scenes/                  # 20 example .rt scene files
 ├── saves/                   # Rendered BMP output directory
 ├── skills/                  # Technical documentation
 ├── .github/workflows/       # CI/CD (GitHub Actions)
@@ -166,13 +168,17 @@ ft_aff() main render loop
                   └── Specular highlights
           ├── Recursive reflection rays (up to MAX_REFLECT_DEPTH=4)
           ├── Refraction rays (Snell's law with IOR)
+          ├── PBR shading (GGX/Cook-Torrance BRDF, Fresnel, metallic-roughness)
+          ├── ACES filmic tone mapping + sRGB gamma
           ├── Texture / bump map sampling
           ├── Depth of field (aperture jitter, DOF_SAMPLES=16)
           └── Motion blur (temporal sampling, MOTION_BLUR_SAMPLES=8)
 ```
 
 Progressive rendering is available: renders at 8x → 4x → 2x → 1x resolution for interactive preview.
 
+Path tracing mode (`--pathtrace N`) features Russian Roulette termination, environment sky lighting, emissive materials, and PBR-aware importance sampling.
+
 ### Supported Shapes (14 types)
 
 #### Basic shapes
@@ -244,6 +250,9 @@ sp  2,0,-5  1.5  255,255,255  trans:0.9 ior:1.5        # Glass sphere
 | `refl:`  | 0–1   | Reflectivity (recursive, max depth 4) |
 | `trans:` | 0–1   | Transparency |
 | `ior:`   | >0    | Index of refraction (used with `trans`) |
+| `metal:` | 0–1   | Metallic factor (PBR metallic-roughness workflow) |
+| `rough:` | 0–1   | Surface roughness (0 = mirror, 1 = matte) |
+| `emit:`  | R,G,B | Emissive light (HDR values allowed, e.g. `emit:500,400,300`) |
 
 ### Memory Management
 
@@ -315,4 +324,29 @@ GitHub Actions pipeline: build validation, unit tests, regression tests, clang-f
 
 ### Scene Files
 
-`scenes/` directory contains 19 test scenes covering basic shapes, extended shapes, quadrics, lighting, interior views, DOF, motion blur, and path tracing.
+`scenes/` directory contains 22 test scenes covering basic shapes, extended shapes, quadrics, lighting, interior views, DOF, motion blur, path tracing, PBR materials, and emissive objects.
+
+## Development Workflow
+
+### Every iteration MUST:
+
+1. **`make lint`** — clang-format check passes
+2. **`make test`** — all unit tests pass (math, camera, intersections, lighting, parsing, PBR)
+3. **`make regression`** — all 19 BMP regression tests pass (requires Xvfb on headless systems: `xvfb-run make regression`)
+
+### When scenes are added or modified:
+
+4. **Re-render `saves/`** — run each changed scene with `-save --output saves/<name>.bmp`
+5. **Regenerate `renders_preview/`** — run `python3 tools/bmp_to_png.py saves/ --output renders_preview/`
+6. **Note:** `scenes/cathedral_ruins.rt` renders at 2560×1440 and takes ~1h. Render in background or last.
+
+### Scene authoring (post-42 scenes only):
+
+All scenes created after the initial 42 project follow the drone-view guidelines documented in **[skills/camera-and-rendering.md](skills/camera-and-rendering.md)** § "Post-42 Scene Generation Rules":
+
+- Elevated camera with downward tilt (`rot_x` 0.12–0.18), **never** `rot_z = ±1`
+- All objects fully visible and well-separated at first glance
+- `E` directive for sky gradient background
+- If rows of items, all rows visible from above (no occlusion)
+
+Original 42 scenes are left unchanged.

Makefile

@@ -84,6 +84,8 @@ SRC_NAME =		ft_mini_rt.c \
 			ft_dof.c \
 			ft_motion.c \
 			ft_pathtrace.c \
+			ft_pbr.c \
+			ft_env.c \
 			ft_close.c \
 			ft_save.c \
 			ft_error.c
@@ -166,15 +168,15 @@ SHAPE_SRCS = ft_sphere.c ft_plane.c ft_square.c \
 TEST_INTERSECT_SRCS = $(TEST_MATH_SRCS) $(SHAPE_SRCS) \
 					  ft_ray_2.c ft_ray.c ft_light.c ft_precompute.c \
 					  ft_bvh.c ft_bvh_2.c \
-					  ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c \
+					  ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c ft_pbr.c ft_env.c \
 					  ft_parsing.c ft_parsing_2.c ft_check_parsing.c \
 					  ft_check_parsing_2.c ft_bzero_struct.c
 
 TEST_PARSING_SRCS = $(TEST_MATH_SRCS) ft_parsing.c ft_parsing_2.c \
 					ft_check_parsing.c ft_check_parsing_2.c ft_bzero_struct.c \
 					$(SHAPE_SRCS) ft_precompute.c \
 					ft_bvh.c ft_bvh_2.c ft_ray.c ft_ray_2.c ft_light.c \
-					ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c
+					ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c ft_pbr.c ft_env.c
 
 TEST_DIR = tests
 
@@ -211,6 +213,12 @@ test:		$(LIB)
 				$(TEST_DIR)/test_parsing.c $(TEST_DIR)/test_stubs.c \
 				$(addprefix $(SRC_DIR)/,$(TEST_PARSING_SRCS)) \
 				$(TEST_LINK) -o run_test_parsing && ./run_test_parsing
+			@echo ""
+			@echo "=== Running PBR tests ==="
+			@$(CC) -Wall -Wextra -Werror -g3 $(MLX_DEF) $(TEST_INC) \
+				$(TEST_DIR)/test_pbr.c $(TEST_DIR)/test_stubs.c \
+				$(addprefix $(SRC_DIR)/,$(TEST_INTERSECT_SRCS)) \
+				$(TEST_LINK) -o run_test_pbr && ./run_test_pbr
 
 COV_FLAGS = -Wall -Wextra -g3 --coverage -fprofile-arcs -ftest-coverage
 
@@ -223,6 +231,7 @@ coverage:	$(LIB)
 				$(TEST_DIR)/test_intersections.c \
 				$(TEST_DIR)/test_lighting.c \
 				$(TEST_DIR)/test_parsing.c \
+				$(TEST_DIR)/test_pbr.c \
 				$(TEST_DIR)/test_stubs.c \
 				$(addprefix $(SRC_DIR)/,$(TEST_INTERSECT_SRCS)) \
 				$(TEST_LINK) -o cov_test_all && ./cov_test_all
@@ -248,7 +257,7 @@ lint:
 TEST_BENCH_SRCS = $(TEST_MATH_SRCS) $(SHAPE_SRCS) \
 				  ft_ray_2.c ft_ray.c ft_light.c ft_precompute.c \
 				  ft_bvh.c ft_bvh_2.c ft_bzero_struct.c \
-				  ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c \
+				  ft_random.c ft_dof.c ft_motion.c ft_pathtrace.c ft_pbr.c ft_env.c \
 				  ft_parsing.c ft_parsing_2.c ft_check_parsing.c \
 				  ft_check_parsing_2.c
 
@@ -264,7 +273,7 @@ gen_scene:
 			@echo "Built gen_scene tool"
 
 testclean:
-			$(RM) run_test_math run_test_camera run_test_intersections run_test_lighting run_test_parsing run_benchmark
+			$(RM) run_test_math run_test_camera run_test_intersections run_test_lighting run_test_parsing run_test_pbr run_benchmark
 			$(RM) cov_test_math cov_test_intersections cov_test_lighting cov_test_parsing cov_test_all
 			$(RM) -r coverage
 			$(RM) *.gcno *.gcda src/*.gcno src/*.gcda tests/*.gcno tests/*.gcda

includes/mini_rt.h

@@ -140,6 +140,9 @@ typedef struct s_material
 	double tex_scale_u;
 	double tex_scale_v;
 	double bump_strength;
+	double metallic;
+	double roughness;
+	t_argb emission;
 	t_texture *texture;
 	t_texture *bump_map;
 	t_pt vel;
@@ -248,6 +251,7 @@ typedef struct s_window
 	int path_trace_spp;
 	int path_trace_bounces;
 	int motion_blur_samples;
+	int use_env_sky;
 } t_window;
 
 typedef struct s_thread_data
@@ -483,6 +487,11 @@ void ft_ray_motion(double i, double j, t_window *win, t_cam *cam);
 
 void ft_pathtrace_pixel(double i, double j, t_window *win, t_cam *cam);
 
+t_argb ft_pbr_shade(t_pt view, t_pt light_dir, t_pt normal, t_material *mat,
+					t_argb light_col, t_argb albedo);
+double ft_fresnel_schlick(double cos_theta, double f0);
+t_argb ft_env_sky(t_pt dir);
+
 int ft_save(t_window *win);
 int ft_file_header(int fd, t_window *rt);
 int ft_info_header(int fd, t_window *rt);

scenes/benchmark.rt

@@ -1,7 +1,8 @@
 R	1920	1080
 A	0.1		255,255,255
+E
 
-c	0,20,-60		0,-0.3,1		70
+c	0,30,60		0.12,0,0		70
 
 l	-30,40,-20		0.8		255,255,200
 l	30,40,-20		0.6		200,200,255

scenes/cathedral_ruins.rt

@@ -1,5 +1,6 @@
 R	2560	1440
 A	0.08	200,190,170
+E
 
 c	0.0,6.0,12.0	0.03,0,0	70
 

scenes/dof_test.rt

@@ -1,5 +1,6 @@
 R	800	600
 A	0.15	255,255,255
+E
 
 c	0,3,15	0.05,0,0	60	aperture:0.15 focal:15.0
 

scenes/materials.rt

@@ -0,0 +1,23 @@
+R   1920  1080
+A   0.1   255,255,255
+E
+c   0,15,35   0.08,0,0   65
+l   -12,28,20   0.8   255,250,240
+l   15,22,30   0.5   220,235,255
+l   0,12,40   0.25   255,255,255
+
+pl  0,-0.5,0   0,1,0   230,230,235
+
+sp  -10,2.5,10   5.0   255,80,80   spec:0.9
+sp  -3,2.5,10   5.0   200,220,255   refl:0.6 spec:0.5
+sp  4,2.5,10   5.0   255,255,255   trans:0.9 ior:1.5 spec:0.3
+sp  11,2.5,10   5.0   220,240,255   trans:0.8 ior:2.4 spec:0.4
+
+sp  -10,2.5,-2   5.0   230,230,240   metal:1.0 rough:0.05 spec:1.0
+sp  -3,2.5,-2   5.0   200,200,210   metal:1.0 rough:0.4 spec:0.7
+sp  4,2.5,-2   5.0   170,150,140   metal:1.0 rough:0.8 spec:0.3
+sp  11,2.5,-2   5.0   50,180,80   metal:0.0 rough:0.1 spec:0.8
+
+bx  -8,3,-14   6,6,6   255,200,100   emit:400,300,200
+cy  0,0,-14   0,1,0   2.5   6.0   180,210,240   metal:0.7 rough:0.2 refl:0.3 spec:0.8
+co  8,0,-14   0,1,0   3.5   6.0   200,180,255   trans:0.5 ior:1.3 spec:0.6

scenes/motion_blur.rt

@@ -1,5 +1,6 @@
 R	800	600
 A	0.15	255,255,255
+E
 
 c	0,5,20	0.05,0,0	60
 

scenes/new_shapes.rt

@@ -1,13 +1,15 @@
 R   1920  1080
 A   0.18   255,255,255
-c   0,4,12   0,-0.15,-1   70
-l   0,20,5   0.45   255,255,255
+E
+c   0,14,28   0.15,0,0   70
+l   -10,25,10   0.55   255,250,240
+l   10,15,20   0.35   220,230,255
 
-sp  -8,1.5,-3   3.0   255,30,30
-co  -4,0,-3   0,1,0   2.0   4.0   30,255,30
-dk  0,2,-5   0,0,1   4.0   255,255,30
-el  4,1.5,-3   2.0,1.2,1.2   30,80,255
-bx  8,1.5,-3   3,3,3   255,140,0
-to  0,5,-8   0,1,0   2.5   0.7   255,30,255
-cy  -6,-0.5,-8   0,1,0   1.5   3.0   0,200,200
+sp  -12,1.5,2   3.0   255,30,30
+co  -6,0,2   0,1,0   2.0   4.0   30,255,30
+dk  0,2,0   0,0,1   4.0   255,255,30
+el  6,1.5,2   2.0,1.2,1.2   30,80,255
+bx  12,1.5,2   3,3,3   255,140,0
+to  -4,4,-6   0,1,0   2.5   0.7   255,30,255
+cy  6,0,-6   0,1,0   1.5   3.0   0,200,200
 pl  0,-1,0   0,1,0   220,220,230

scenes/pbr_showcase.rt

@@ -0,0 +1,23 @@
+R   1920  1080
+A   0.12   255,255,255
+E
+c   0,16,38   0.07,0,0   65
+l   -15,30,25   0.85   255,250,240
+l   20,25,35   0.55   220,235,255
+l   0,15,50   0.3   255,255,255
+
+pl  0,-0.5,0   0,1,0   230,230,235
+
+sp  -12,2.5,14   5.0   230,30,30   spec:0.8
+sp  -4,2.5,14   5.0   30,200,60   spec:0.5
+sp  4,2.5,14   5.0   40,80,230   spec:0.3
+sp  12,2.5,14   5.0   255,255,255   trans:0.9 ior:1.5
+
+sp  -12,2.5,0   5.0   240,240,245   metal:1.0 rough:0.05 spec:1.0
+sp  -4,2.5,0   5.0   210,210,220   metal:1.0 rough:0.3 spec:0.8
+sp  4,2.5,0   5.0   180,160,150   metal:1.0 rough:0.6 spec:0.5
+sp  12,2.5,0   5.0   230,150,90   metal:1.0 rough:0.9 spec:0.3
+
+bx  -10,3,-14   6,6,6   255,210,60   metal:1.0 rough:0.2 spec:0.9
+cy  0,0,-14   0,1,0   3.0   7.0   180,220,255   metal:0.7 rough:0.15 spec:0.9
+co  10,0,-14   0,1,0   4.0   7.0   100,255,140   metal:0.5 rough:0.3 spec:0.7

scenes/quadrics.rt

@@ -1,11 +1,13 @@
 R   1920  1080
 A   0.25   255,255,255
-c   0,5,14   0,-0.2,-1   70
+E
+c   0,14,24   0.15,0,0   70
 l   -3,20,8   0.60   255,255,255
+l   5,15,15   0.35   220,230,255
 
-hy  -5,2,-4   0,1,0   1.5,2.0,0   6.0   255,80,30
-pa  0,0,-4   0,1,0   0.8   5.0   30,200,255
-co  5,0,-4   0,1,0   2.5   5.0   80,255,80
-sp  -5,6,-4   1.0   255,255,100
-bx  5,5.5,-4   1.5,1.5,1.5   255,100,255
+hy  -8,2,0   0,1,0   1.5,2.0,0   6.0   255,80,30
+pa  0,0,0   0,1,0   0.8   5.0   30,200,255
+co  8,0,0   0,1,0   2.5   5.0   80,255,80
+sp  -4,6,0   1.0   255,255,100
+bx  4,5.5,0   1.5,1.5,1.5   255,100,255
 pl  0,-1,0   0,1,0   220,220,230

scenes/taurus.rt

@@ -1,5 +1,6 @@
 R   1920  1080
 A   0.08   255,255,255
+E
 c   0,14,20   0.2,0,0   60
 l   -10,20,20   0.5   255,245,235
 l   10,18,15   0.4   235,240,255

skills/camera-and-rendering.md

@@ -139,6 +139,45 @@ DISPLAY=:42 ./miniRT scene.rt -save
 - Neutral wall/plane colors of 150–200 work better than 220–240 for scenes with white/reflective objects
 - At least 2 lights from different angles improves depth perception
 
+## Post-42 Scene Generation Rules
+
+All scenes created after the initial 42 project **MUST** follow these rules. Original 42 scenes (cylinder, exemple, inside_cy, inside_cy_l, inside_sp, inside_sp_l, lights, objects, square, tiny, triangle, error) are left as-is.
+
+### Drone-view camera placement
+
+Every showcase scene uses an elevated "drone view" where **all objects are fully visible at first glance**:
+
+| Parameter | Rule | Typical range |
+|-----------|------|---------------|
+| Camera Y | max_object_height + 8–12 | 12–16 |
+| Camera Z | furthest_object_z + scene_x_span × 0.8 | 20–40 |
+| rot_x (pitch) | 0.12–0.18 (22°–32° downward tilt) | 0.15 |
+| rot_y (yaw) | 0 always | 0 |
+| rot_z (roll) | 0 always (**never** ±1) | 0 |
+| FOV | 65–70° | 70 |
+
+**Checklist for row-based layouts** (e.g. materials, pbr_showcase):
+- All objects in every row must be fully visible — no clipping at frame edges
+- Clear ground visible between rows (at least 4–6 units of Z separation)
+- Camera high enough that rear rows are not occluded by front rows
+
+### Sky background
+
+Add the `E` directive (on its own line, after `A`) to enable the gradient sky. This replaces the black void with a blue-to-white horizon gradient.
+
+```
+R   1920  1080
+A   0.15   255,255,255
+E
+c   0,14,28   0.15,0,0   70
+```
+
+### Object layout
+
+- Spread objects along X with at least 1 diameter of spacing between them
+- Use 2+ lights from different angles for depth/shadow separation
+- Ground plane color: light gray (220–235) to contrast with objects and sky
+
 ### Material properties (parsed in `ft_material.c`)
 
 Appended to shape lines as `key:value` pairs:
@@ -149,6 +188,9 @@ Appended to shape lines as `key:value` pairs:
 | `refl:` | 0–1 | Reflectivity (recursive ray tracing, max depth 4) |
 | `trans:` | 0–1 | Transparency |
 | `ior:` | >0 | Index of refraction (used with trans) |
+| `metal:` | 0–1 | Metallic factor (PBR metallic-roughness workflow) |
+| `rough:` | 0–1 | Surface roughness (0 = mirror, 1 = matte) |
+| `emit:` | R,G,B | Emissive light (HDR values allowed, e.g. `emit:500,400,300`) |
 
 ### Supported shape IDs