Start implementing drawing order

compile

@@ -12,6 +12,7 @@ RAYTRACER_SRC="src/window/*.c \
 	src/raytracer/*.c \
 	src/math/*.c \
 	src/camera/*.c \
+	$WAPP_SRC \
 "
 
 RASTERISER_SRC="src/window/*.c \

include/rasteriser/rasteriser.h

@@ -31,7 +31,8 @@ MAKE_LIST_TYPE(scene_triangle_t);
 
 typedef enum {
   RASTERISER_RENDER_WIREFRAME,
-  RASTERISER_RENDER_SOLID,
+  RASTERISER_RENDER_FILLED,
+  RASTERISER_RENDER_SHADED,
 } render_type_t;
 
 typedef struct {
@@ -46,6 +47,9 @@ typedef struct {
   f32 h0;
   f32 h1;
   f32 h2;
+  f32 z0;
+  f32 z1;
+  f32 z2;
   colour_t colour;
 } triangle_t;
 

include/window/window.h

@@ -2,6 +2,7 @@
 #define WINDOW_H
 
 #include "aliases.h"
+#include "mem_arena.h"
 #include "vector/vec.h"
 #include <SDL2/SDL_video.h>
 #include <stdbool.h>
@@ -29,13 +30,17 @@ typedef struct {
   SDL_Window *window;
   SDL_Surface *front_buffer;
   SDL_Surface *back_buffer;
+  f32 *z_buffer;
 } window_t;
 
-bool init_window(window_t *wnd, u32 width, u32 height, const char *title);
+bool init_window(Arena *arena, window_t *wnd, u32 width, u32 height,
+                 const char *title);
 void close_window(window_t *wnd);
 
 void clear_window(window_t *wnd, colour_t colour);
 void set_pixel(window_t *wnd, i32 x, i32 y, colour_t colour);
+void set_z_pixel(window_t *wnd, i32 x, i32 y, f32 value);
+f32 get_z_pixel(const window_t *wnd, i32 x, i32 y);
 void swap_buffers(window_t *wnd);
 
 vec3f_t window_to_viewport(const window_t *wnd, i32 x, i32 y, vec3f_t viewport);

src/rasteriser/main.c

@@ -20,12 +20,6 @@ int main(void) {
   };
   vec3f_t viewport = {.x = 1.0f, .y = 1.0f, .z = 1.0f};
 
-  window_t window = {0};
-
-  if (!init_window(&window, 800, 800, "CG From Scratch Rasteriser")) {
-    return EXIT_FAILURE;
-  }
-
   Arena *arena = NULL;
   u64 main_arena_capacity = 64ull * 1024ull * 1024ull * 1024ull;
   if (!wapp_mem_arena_init(&arena, main_arena_capacity, WAPP_MEM_ALLOC_RESERVE,
@@ -33,6 +27,12 @@ int main(void) {
     return EXIT_FAILURE;
   }
 
+  window_t window = {0};
+
+  if (!init_window(arena, &window, 800, 800, "CG From Scratch Rasteriser")) {
+    return EXIT_FAILURE;
+  }
+
   list_vertex_t *vertices = list_create(vertex_t, arena);
   if (!vertices) {
     return EXIT_FAILURE;
@@ -181,7 +181,7 @@ int main(void) {
 
     clear_window(&window, bg);
 
-    render_scene(&window, frame_arena, &scene, RASTERISER_RENDER_SOLID);
+    render_scene(&window, frame_arena, &scene, RASTERISER_RENDER_FILLED);
 
     swap_buffers(&window);
 

src/rasteriser/rasteriser.c

@@ -121,16 +121,23 @@ internal void render_instance(window_t *wnd, const rasteriser_scene_t *scene,
     list_append(vec2i_t, arena, projected, point);
   }
 
+  vertex_t v0, v1, v2;
   for (u64 i = 0; i < triangles->count; ++i) {
     scene_triangle_t triangle = list_get(triangles, i);
+    v0 = list_get(transformed, triangle.idx0);
+    v1 = list_get(transformed, triangle.idx1);
+    v2 = list_get(transformed, triangle.idx2);
 
     triangle_t tri = {
         .p0 = list_get(projected, triangle.idx0),
         .p1 = list_get(projected, triangle.idx1),
         .p2 = list_get(projected, triangle.idx2),
-        .h0 = list_get(transformed, triangle.idx0).h,
-        .h1 = list_get(transformed, triangle.idx1).h,
-        .h2 = list_get(transformed, triangle.idx2).h,
+        .h0 = v0.h,
+        .h1 = v1.h,
+        .h2 = v2.h,
+        .z0 = v0.position.z,
+        .z1 = v1.position.z,
+        .z2 = v2.position.z,
         .colour = triangle.colour,
     };
 
@@ -143,9 +150,12 @@ internal void render_instance(window_t *wnd, const rasteriser_scene_t *scene,
     case RASTERISER_RENDER_WIREFRAME:
       draw_wireframe_triangle(wnd, arena, tri);
       break;
-    case RASTERISER_RENDER_SOLID:
+    case RASTERISER_RENDER_FILLED:
       draw_filled_triangle(wnd, arena, tri);
       break;
+    case RASTERISER_RENDER_SHADED:
+      draw_shaded_triangle(wnd, arena, tri);
+      break;
     }
   }
 }
@@ -176,22 +186,57 @@ void draw_filled_triangle(window_t *wnd, Arena *arena, triangle_t triangle) {
   list_pop(x01); // Last element of x01 is a duplicate of first element in x12
   list_merge(f32, arena, x012, x01, x12);
 
+  f32 z0 = triangle.z0;
+  f32 z1 = triangle.z1;
+  f32 z2 = triangle.z2;
+  list_float *z01 = interpolate(arena, y0, z0, y1, z1);
+  list_float *z12 = interpolate(arena, y1, z1, y2, z2);
+  list_float *z02 = interpolate(arena, y0, z0, y2, z2);
+  list_float *z012 = NULL;
+
+  list_pop(z01); // Last element of z01 is a duplicate of first element in z12
+  list_merge(f32, arena, z012, z01, z12);
+
   list_float *x_left;
   list_float *x_right;
+  list_float *z_left;
+  list_float *z_right;
   u64 middle = (u64)(floorf((f32)(x02->count) / 2.0f));
   if (list_get(x02, middle) < list_get(x012, middle)) {
     x_left = x02;
+    z_left = z02;
     x_right = x012;
+    z_right = z012;
   } else {
     x_left = x012;
+    z_left = z012;
     x_right = x02;
+    z_right = z02;
   }
 
+  list_float *z_segment = NULL;
+  i32 index = -1;
+  i64 xl = -1;
+  i64 xr = -1;
+  f32 current_z = INFINITY;
+  f32 new_z = INFINITY;
+
   for (i64 y = y0; y <= y2; ++y) {
-    i32 index = y - y0;
-    for (i64 x = (i64)list_get(x_left, index); x < list_get(x_right, index);
-         ++x) {
-      set_pixel(wnd, x, y, triangle.colour);
+    index = y - y0;
+    xl = (i64)list_get(x_left, index);
+    xr = (i64)list_get(x_right, index);
+
+    for (i64 x = xl; x < xr; ++x) {
+      z_segment = interpolate(arena, xl, list_get(z_left, index), xr,
+                              list_get(z_right, index));
+
+      current_z = get_z_pixel(wnd, x, y);
+      new_z = list_get(z_segment, x - xl);
+
+      if (new_z <= current_z) {
+        set_z_pixel(wnd, x, y, new_z);
+        set_pixel(wnd, x, y, triangle.colour);
+      }
     }
   }
 }
@@ -225,27 +270,47 @@ void draw_shaded_triangle(window_t *wnd, Arena *arena, triangle_t triangle) {
   list_pop(h01); // Last element of h01 is a duplicate of first element in h12
   list_merge(f32, arena, h012, h01, h12);
 
+  f32 z0 = triangle.z0;
+  f32 z1 = triangle.z1;
+  f32 z2 = triangle.z2;
+  list_float *z01 = interpolate(arena, y0, z0, y1, z1);
+  list_float *z12 = interpolate(arena, y1, z1, y2, z2);
+  list_float *z02 = interpolate(arena, y0, z0, y2, z2);
+  list_float *z012 = NULL;
+
+  list_pop(z01); // Last element of z01 is a duplicate of first element in z12
+  list_merge(f32, arena, z012, z01, z12);
+
   list_float *x_left;
   list_float *x_right;
   list_float *h_left;
   list_float *h_right;
+  list_float *z_left;
+  list_float *z_right;
   u64 middle = (u64)(floorf((f32)(x02->count) / 2.0f));
   if (list_get(x02, middle) < list_get(x012, middle)) {
     x_left = x02;
     h_left = h02;
+    z_left = z02;
     x_right = x012;
     h_right = h012;
+    z_right = z012;
   } else {
     x_left = x012;
     h_left = h012;
+    z_left = z012;
     x_right = x02;
     h_right = h02;
+    z_right = z02;
   }
 
   list_float *h_segment = NULL;
+  list_float *z_segment = NULL;
   i32 index = -1;
   i64 xl = -1;
   i64 xr = -1;
+  f32 current_z = INFINITY;
+  f32 new_z = INFINITY;
   colour_t shaded_colour = (colour_t){0};
 
   for (i64 y = y0; y <= y2; ++y) {
@@ -255,8 +320,17 @@ void draw_shaded_triangle(window_t *wnd, Arena *arena, triangle_t triangle) {
     for (i64 x = xl; x < xr; ++x) {
       h_segment = interpolate(arena, xl, list_get(h_left, index), xr,
                               list_get(h_right, index));
+      z_segment = interpolate(arena, xl, list_get(z_left, index), xr,
+                              list_get(z_right, index));
       shaded_colour = colour_mul(triangle.colour, list_get(h_segment, x - xl));
-      set_pixel(wnd, x, y, shaded_colour);
+
+      current_z = get_z_pixel(wnd, x, y);
+      new_z = list_get(z_segment, x - xl);
+
+      if (new_z <= current_z) {
+        set_z_pixel(wnd, x, y, new_z);
+        set_pixel(wnd, x, y, shaded_colour);
+      }
     }
   }
 }

src/raytracer/main.c

@@ -22,7 +22,7 @@ i32 main(i32 argc, char *argv[]) {
 
   window_t window = {0};
 
-  if (!init_window(&window, 800, 800, "CG From Scratch Raytracer")) {
+  if (!init_window(NULL, &window, 800, 800, "CG From Scratch Raytracer")) {
     return EXIT_FAILURE;
   }
 

src/window/window.c

@@ -1,21 +1,25 @@
 #include "window/window.h"
 #include "aliases.h"
 #include "math/math_utils.h"
+#include "mem_arena.h"
 #include "vector/vec.h"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_error.h>
 #include <SDL2/SDL_pixels.h>
 #include <SDL2/SDL_surface.h>
+#include <math.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 
-u32 index_from_coordinates(window_t *wnd, u32 x, u32 y);
+u32 index_from_coordinates(const window_t *wnd, u32 x, u32 y);
 i32 denormalise(i32 value, u32 max, u32 abs_half);
 vec2i_t denormalised_coords(const window_t *wnd, i32 x, i32 y);
 void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour);
+void set_z_buffer_pixel(window_t *wnd, u32 x, u32 y, f32 value);
 
-bool init_window(window_t *wnd, u32 width, u32 height, const char *title) {
+bool init_window(Arena *arena, window_t *wnd, u32 width, u32 height,
+                 const char *title) {
   if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
     printf("Failed to initialise SDL: %s\n", SDL_GetError());
 
@@ -64,6 +68,9 @@ bool init_window(window_t *wnd, u32 width, u32 height, const char *title) {
   wnd->half_width = width / 2;
   wnd->half_height = height / 2;
   wnd->title = title;
+  if (arena) {
+    wnd->z_buffer = wapp_mem_arena_alloc(arena, width * height * sizeof(f32));
+  }
 
   return true;
 }
@@ -85,6 +92,8 @@ void close_window(window_t *wnd) {
 
       wnd->back_buffer = NULL;
     }
+
+    wnd->z_buffer = NULL;
   }
 
   SDL_Quit();
@@ -98,6 +107,7 @@ void clear_window(window_t *wnd, colour_t colour) {
 
   for (u32 i = 0; i < count; ++i) {
     pixels[i] = colour.colour;
+    wnd->z_buffer[i] = INFINITY;
   }
 
   SDL_UnlockSurface(wnd->back_buffer);
@@ -117,13 +127,34 @@ void set_pixel(window_t *wnd, i32 x, i32 y, colour_t colour) {
   SDL_UnlockSurface(wnd->back_buffer);
 }
 
+void set_z_pixel(window_t *wnd, i32 x, i32 y, f32 value) {
+  vec2i_t coords = denormalised_coords(wnd, x, y);
+
+  if (coords.x < 0 || coords.y < 0) {
+    return;
+  }
+
+  set_z_buffer_pixel(wnd, (u32)(coords.x), (u32)(coords.y), value);
+}
+
+f32 get_z_pixel(const window_t *wnd, i32 x, i32 y) {
+  vec2i_t coords = denormalised_coords(wnd, x, y);
+
+  if (coords.x < 0 || coords.y < 0) {
+    return INFINITY;
+  }
+
+  u32 index = index_from_coordinates(wnd, (u32)(coords.x), (u32)(coords.y));
+  return wnd->z_buffer[index];
+}
+
 void swap_buffers(window_t *wnd) {
   SDL_BlitSurface(wnd->back_buffer, NULL, wnd->front_buffer, NULL);
 
   SDL_UpdateWindowSurface(wnd->window);
 }
 
-u32 index_from_coordinates(window_t *wnd, u32 x, u32 y) {
+u32 index_from_coordinates(const window_t *wnd, u32 x, u32 y) {
   return y * wnd->width + x;
 }
 
@@ -159,6 +190,11 @@ void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour) {
   pixels[index] = colour.colour;
 }
 
+void set_z_buffer_pixel(window_t *wnd, u32 x, u32 y, f32 value) {
+  u32 index = index_from_coordinates(wnd, x, y);
+  wnd->z_buffer[index] = value;
+}
+
 vec3f_t window_to_viewport(const window_t *wnd, i32 x, i32 y,
                            vec3f_t viewport) {
   return (vec3f_t){