Refactor shader code and implement fragment shaders

src/img.c

@@ -7,7 +7,7 @@
 #include <stddef.h>
 #include <string.h>
 
-internal u64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y, u64 base_size);
+internal i64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y, u64 base_size);
 
 bool _init_buffer(Arena *arena, Buffer *buffer, u64 base_size) {
   if (!arena || !buffer || buffer->width == 0 || buffer->height == 0) {
@@ -21,12 +21,20 @@ bool _init_buffer(Arena *arena, Buffer *buffer, u64 base_size) {
 }
 
 u8 *_get_pixel(Buffer *buffer, u64 x, u64 y, u64 base_size) {
-  u64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  i64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  if (idx == -1) {
+    idx = 0;
+  }
+
   return ((u8 *)(buffer->buf)) + idx;
 }
 
 void _set_pixel(Buffer *buffer, u64 x, u64 y, void *value, u64 base_size) {
-  u64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  i64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  if (idx == -1) {
+    return;
+  }
+
   memcpy(((u8 *)(buffer->buf)) + idx, value, base_size);
   return;
 }
@@ -75,7 +83,11 @@ void save_image(const Image *img, const char *filename) {
   write_p7_image(img->width, img->height, (u8 *)(img->buf), filename);
 }
 
-internal u64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y,
+internal i64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y,
                                    u64 base_size) {
+  if (x < 0 || y < 0 || x >= buffer->width || y >= buffer->height) {
+    return -1;
+  }
+
   return (y * buffer->width + x) * base_size;
 }

src/obj.c

@@ -3,6 +3,7 @@
 #include "img.h"
 #include "mem_arena.h"
 #include "pam.h"
+#include "shader.h"
 #include "typed_list.h"
 #include "utils.h"
 #include "vec.h"
@@ -23,9 +24,10 @@ struct triangle_bbox {
 };
 
 internal void render_triangle(const Triangle *triangle, const Model *model,
-                              const Shader *shader, Render *render,
+                              ShaderID shader, Render *render,
                               RenderType render_type, Colour colour);
-internal void fill_triangle(Render *render, V3f vertices[TRIANGLE_VERTICES],
+internal void fill_triangle(Render *render, ShaderID shader,
+                            V3f vertices[TRIANGLE_VERTICES],
                             V3f normals[TRIANGLE_VERTICES],
                             V2f coordinates[TRIANGLE_VERTICES], Colour colour,
                             Image *texture, RenderType type);
@@ -36,8 +38,6 @@ internal V3f get_barycentric_coords(f32 d00, f32 d01, f32 d11, f32 denom,
                                     const V2i *ap);
 internal V3f get_viewport_vertex(const V3f *vertex, const Image *img);
 
-V3f g_light_dir = {0.0f, 0.0f, 1.0f};
-
 Model load_obj_file(Arena *arena, const char *filename, const char *texture) {
   if (!arena) {
     return INVALID_MODEL;
@@ -131,7 +131,7 @@ bool init_render(Arena *arena, Render *render, u64 width, u64 height) {
   return true;
 }
 
-void render_model(const Model *model, Render *render, const Shader *shader,
+void render_model(const Model *model, Render *render, ShaderID shader,
                   RenderType render_type, Colour colour) {
   Triangle triangle;
   for (u64 i = 0; i < model->triangles->count; ++i) {
@@ -141,7 +141,7 @@ void render_model(const Model *model, Render *render, const Shader *shader,
 }
 
 internal void render_triangle(const Triangle *triangle, const Model *model,
-                              const Shader *shader, Render *render,
+                              ShaderID shader, Render *render,
                               RenderType render_type, Colour colour) {
   Image *img = &(render->img);
   V3f vertices[TRIANGLE_VERTICES] = {
@@ -161,8 +161,8 @@ internal void render_triangle(const Triangle *triangle, const Model *model,
   };
 
   for (u64 i = 0; i < TRIANGLE_VERTICES; ++i) {
-    vertices[i] = shader->vertex(&vertices[i], shader->model_view,
-                                 shader->projection, &render->img);
+    vertices[i] =
+        run_vertex_shader(shader, &vertices[i], (Buffer *)&render->img);
   }
 
   if (render_type == RENDER_TYPE_WIREFRAME) {
@@ -176,12 +176,13 @@ internal void render_triangle(const Triangle *triangle, const Model *model,
     }
   } else if (render_type == RENDER_TYPE_FILLED ||
              render_type == RENDER_TYPE_SHADED) {
-    fill_triangle(render, vertices, normals, coordinates, colour,
+    fill_triangle(render, shader, vertices, normals, coordinates, colour,
                   model->texture, render_type);
   }
 }
 
-internal void fill_triangle(Render *render, V3f vertices[TRIANGLE_VERTICES],
+internal void fill_triangle(Render *render, ShaderID shader,
+                            V3f vertices[TRIANGLE_VERTICES],
                             V3f normals[TRIANGLE_VERTICES],
                             V2f coordinates[TRIANGLE_VERTICES], Colour colour,
                             Image *texture, RenderType type) {
@@ -207,6 +208,8 @@ internal void fill_triangle(Render *render, V3f vertices[TRIANGLE_VERTICES],
   V3f normal;
   f32 tx_u, tx_v;
   u64 tx_x, tx_y;
+  V2f tex_coords;
+  FragmentResult result;
 
   f32 intensity = 1.0f;
 
@@ -222,8 +225,10 @@ internal void fill_triangle(Render *render, V3f vertices[TRIANGLE_VERTICES],
       z += v0.z * coords.x + v1.z * coords.y + v2.z * coords.z;
       zbuf = get_pixel(f32, &(render->depth), x, y);
 
-      if (z > zbuf) {
-        if (type == RENDER_TYPE_SHADED) {
+      if (z <= zbuf) {
+        continue;
+      }
+
       nx = normals[0].x * coords.x + normals[1].x * coords.y +
            normals[2].x * coords.z;
       ny = normals[0].y * coords.x + normals[1].y * coords.y +
@@ -231,31 +236,21 @@ internal void fill_triangle(Render *render, V3f vertices[TRIANGLE_VERTICES],
       nz = normals[0].z * coords.x + normals[1].z * coords.y +
            normals[2].z * coords.z;
       normal = (V3f){nx, ny, nz};
-          intensity = dot_v3(normal, g_light_dir);
-        }
 
-        if (intensity < 0.0f) {
-          intensity = 0.01f;
-        }
-
-        if (texture) {
       tx_u = coordinates[0].u * coords.x + coordinates[1].u * coords.y +
              coordinates[2].u * coords.z;
       tx_v = coordinates[0].v * coords.x + coordinates[1].v * coords.y +
              coordinates[2].v * coords.z;
-          tx_x = tx_u * texture->width;
-          tx_y = (1.0f - tx_v) * texture->height;
+      tex_coords = (V2f){tx_u, tx_v};
 
-          colour = get_pixel(Colour, texture, tx_x, tx_y);
+      result =
+          run_fragment_shader(shader, normal, tex_coords, &colour, texture);
+      if (DISCARD_FRAGMENT(result)) {
+        continue;
       }
 
-        colour.r *= intensity;
-        colour.g *= intensity;
-        colour.b *= intensity;
-
       set_pixel(depth, x, y, &z);
-        set_pixel(img, x, y, &colour);
-      }
+      set_pixel(img, x, y, &result.colour);
     }
   }
 }

src/obj.h

@@ -57,7 +57,7 @@ struct render {
 
 Model load_obj_file(Arena *arena, const char *filename, const char *texture);
 bool init_render(Arena *arena, Render *render, u64 width, u64 height);
-void render_model(const Model *model, Render *render, const Shader *shader,
+void render_model(const Model *model, Render *render, ShaderID shader,
                   RenderType render_type, Colour colour);
 
 #endif // OBJ_H

src/shader.c

@@ -0,0 +1,62 @@
+#include "shader.h"
+#include "aliases.h"
+#include "vec.h"
+
+#define MAX_SHADER_COUNT 2048
+
+typedef struct shader_repo ShaderRepo;
+struct shader_repo {
+  void *shaders[MAX_SHADER_COUNT];
+  VertexShader *vertex_funcs[MAX_SHADER_COUNT];
+  FragmentShader *fragment_funcs[MAX_SHADER_COUNT];
+  u64 count;
+};
+
+internal ShaderRepo g_repository = {0};
+
+ShaderID create_shader(void *shader, VertexShader *vertex,
+                       FragmentShader *fragment) {
+  if (g_repository.count + 1 >= MAX_SHADER_COUNT) {
+    return INVALID_SHADER;
+  }
+
+  ++(g_repository.count);
+  g_repository.shaders[g_repository.count] = shader;
+  g_repository.vertex_funcs[g_repository.count] = vertex;
+  g_repository.fragment_funcs[g_repository.count] = fragment;
+
+  return (ShaderID){g_repository.count};
+}
+
+V3f run_vertex_shader(ShaderID shader, const V3f *vertex,
+                      const Buffer *out_buf) {
+  if (IS_INVALID_SHADER(shader) || shader.id > g_repository.count || !vertex ||
+      !out_buf) {
+    return (V3f){0};
+  }
+
+  void *shader_obj = g_repository.shaders[shader.id];
+  VertexShader *vertex_func = g_repository.vertex_funcs[shader.id];
+
+  if (!shader_obj || !vertex_func) {
+    return (V3f){0};
+  }
+
+  return vertex_func(shader_obj, vertex, out_buf);
+}
+
+FragmentResult run_fragment_shader(ShaderID shader, V3f normal, V2f tex_coords,
+                                   const Colour *colour, const Image *texture) {
+  if (IS_INVALID_SHADER(shader) || shader.id > g_repository.count || !colour) {
+    return DISCARDED_FRAGMENT;
+  }
+
+  void *shader_obj = g_repository.shaders[shader.id];
+  FragmentShader *fragment_func = g_repository.fragment_funcs[shader.id];
+
+  if (!shader_obj || !fragment_func) {
+    return DISCARDED_FRAGMENT;
+  }
+
+  return fragment_func(shader_obj, normal, tex_coords, colour, texture);
+}

src/shader.h

@@ -1,19 +1,37 @@
 #ifndef SHADER_H
 #define SHADER_H
 
+#include "aliases.h"
 #include "img.h"
 #include "vec.h"
 
-typedef V3f(VertexShader)(const V3f *vertex, M4x4f *model_view,
-                          M4x4f *projection, const Image *img);
-typedef bool(FragmentShader)(Colour colour);
-
-typedef struct shader Shader;
-struct shader {
-  VertexShader *vertex;
-  FragmentShader *fragment;
-  M4x4f *model_view;
-  M4x4f *projection;
+typedef struct shader_id ShaderID;
+struct shader_id {
+  u64 id;
 };
 
+typedef struct fragment_result FragmentResult;
+struct fragment_result {
+  Colour colour;
+  bool discard;
+};
+
+#define INVALID_SHADER ((ShaderID){0})
+#define IS_INVALID_SHADER(ID) (ID.id == 0)
+#define DISCARDED_FRAGMENT ((FragmentResult){.discard = true})
+#define DISCARD_FRAGMENT(RESULT) (RESULT.discard)
+
+typedef V3f(VertexShader)(void *shader, const V3f *vertex,
+                          const Buffer *out_buf);
+typedef FragmentResult(FragmentShader)(void *shader, V3f normal, V2f tex_coords,
+                                       const Colour *colour,
+                                       const Image *texture);
+
+ShaderID create_shader(void *shader, VertexShader *vertex,
+                       FragmentShader *fragment);
+V3f run_vertex_shader(ShaderID shader, const V3f *vertex,
+                      const Buffer *out_buf);
+FragmentResult run_fragment_shader(ShaderID shader, V3f normal, V2f tex_coords,
+                                   const Colour *colour, const Image *texture);
+
 #endif // SHADER_H