Add perspective projection support

src/obj.c

@@ -12,6 +12,7 @@
 #include <string.h>
 
 #define TRIANGLE_VERTICES 3
+#define CAMERA_DISTANCE 5.0f
 
 #define V2(T, ELEM_T, X0, Y0, X1, Y1)                                          \
   ((T){(ELEM_T)X1 - (ELEM_T)X0, (ELEM_T)Y1 - (ELEM_T)Y0})
@@ -62,6 +63,14 @@ struct f32x3 {
   f32 z;
 };
 
+typedef struct f32x4 V4f;
+struct f32x4 {
+  f32 x;
+  f32 y;
+  f32 z;
+  f32 w;
+};
+
 typedef struct u64x3 V3u;
 struct u64x3 {
   u64 x;
@@ -76,8 +85,17 @@ struct f32_3x3 {
   V3f row2;
 };
 
+typedef struct f32_4x4 M4x4f;
+struct f32_4x4 {
+  V4f row0;
+  V4f row1;
+  V4f row2;
+  V4f row3;
+};
+
 internal void render_triangle(const Triangle *triangle, const Model *model,
-                              Render *render, Colour colour, RenderType type);
+                              Render *render, Colour colour, RenderType type,
+                              ProjectionType projection);
 internal void fill_triangle(Render *render, Vertex vertices[TRIANGLE_VERTICES],
                             TexCoord coordinates[TRIANGLE_VERTICES],
                             Colour colour, f32 intensity, Image *texture);
@@ -94,6 +112,15 @@ internal u64 ndc_to_image_coordinate(f32 value, u64 max);
 
 V3f g_light_dir = {0.0f, 0.0f, -1.0f};
 
+// clang-format off
+M4x4f g_cam_matrix = {
+  .row0 = {1.0f, 0.0f,                    0.0f, 0.0f},
+  .row1 = {0.0f, 1.0f,                    0.0f, 0.0f},
+  .row2 = {0.0f, 0.0f,                    1.0f, 0.0f},
+  .row3 = {0.0f, 0.0f, -1.0f / CAMERA_DISTANCE, 1.0f},
+};
+// clang-format on
+
 Model load_obj_file(Arena *arena, const char *filename, const char *texture) {
   if (!arena) {
     return NULL_MODEL;
@@ -177,7 +204,8 @@ bool init_render(Arena *arena, Render *render, u64 width, u64 height) {
 }
 
 void render_model(const Model *model, Render *render, Colour colour,
-                  RenderType type, ColourType colour_type) {
+                  RenderType type, ColourType colour_type,
+                  ProjectionType projection) {
   Triangle triangle;
 
   for (u64 i = 0; i < model->triangles->count; ++i) {
@@ -188,12 +216,13 @@ void render_model(const Model *model, Render *render, Colour colour,
                         .b = rand() % UINT8_MAX,
                         .a = 255};
     }
-    render_triangle(&triangle, model, render, colour, type);
+    render_triangle(&triangle, model, render, colour, type, projection);
   }
 }
 
 internal void render_triangle(const Triangle *triangle, const Model *model,
-                              Render *render, Colour colour, RenderType type) {
+                              Render *render, Colour colour, RenderType type,
+                              ProjectionType projection) {
   Image *img = &(render->img);
   Vertex vertices[TRIANGLE_VERTICES] = {
       list_get(model->vertices, triangle->p0),

src/obj.h

@@ -47,6 +47,13 @@ typedef enum {
   COUNT_COLOUR_TYPE,
 } ColourType;
 
+typedef enum {
+  PROJECTION_TYPE_ORTHOGRAPHIC,
+  PROJECTION_TYPE_PERSPECTIVE,
+
+  COUNT_PROJECTION_TYPE,
+} ProjectionType;
+
 MAKE_LIST_TYPE(Vertex);
 MAKE_LIST_TYPE(TexCoord);
 MAKE_LIST_TYPE(Triangle);
@@ -68,6 +75,7 @@ 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, Colour colour,
-                  RenderType type, ColourType colour_type);
+                  RenderType type, ColourType colour_type,
+                  ProjectionType projection);
 
 #endif // OBJ_H