Implement perspective projection

src/main.c

@@ -39,7 +39,8 @@ int main(void) {
   }
 
   clear_buffer(&(render.img), &bg);
-  render_model(&obj, &render, teal, RENDER_TYPE_SHADED, COLOUR_TYPE_FIXED);
+  render_model(&obj, &render, teal, RENDER_TYPE_SHADED, COLOUR_TYPE_FIXED,
+               PROJECTION_TYPE_PERSPECTIVE);
   save_image(&(render.img), "result.pam");
 
   wapp_mem_arena_destroy(&arena);

src/obj.c

@@ -35,6 +35,19 @@
       .y = V1.z * V2.x - V1.x * V2.z,                                          \
       .z = V1.x * V2.y - V1.y * V2.x,                                          \
   })
+#define mat4x4_mul_vec4(MAT, V)                                                \
+  ((V4f){                                                                      \
+      .x = MAT.row0.x * V.x + MAT.row0.y * V.y + MAT.row0.z * V.z +            \
+           MAT.row0.w * V.w,                                                   \
+      .y = MAT.row1.x * V.x + MAT.row1.y * V.y + MAT.row1.z * V.z +            \
+           MAT.row1.w * V.w,                                                   \
+      .z = MAT.row2.x * V.x + MAT.row2.y * V.y + MAT.row2.z * V.z +            \
+           MAT.row2.w * V.w,                                                   \
+      .w = MAT.row3.x * V.x + MAT.row3.y * V.y + MAT.row3.z * V.z +            \
+           MAT.row3.w * V.w,                                                   \
+  })
+#define project_vec4(V) ((V3f){.x = V.x / V.w, .y = V.y / V.w, .z = V.z / V.w})
+#define vec3_to_vertex(V) ((Vertex){.x = V.x, .y = V.y, .z = V.z})
 
 typedef struct triangle_bbox TriangleBBox;
 struct triangle_bbox {
@@ -235,6 +248,23 @@ internal void render_triangle(const Triangle *triangle, const Model *model,
       list_get(model->texture_coordinates, triangle->tx2),
   };
 
+  if (projection == PROJECTION_TYPE_PERSPECTIVE) {
+    // Basic perspective projection
+    V4f vertex;
+    V3f projected;
+    for (u64 i = 0; i < TRIANGLE_VERTICES; ++i) {
+      vertex = (V4f){
+          .x = vertices[i].x,
+          .y = vertices[i].y,
+          .z = vertices[i].z,
+          .w = 1.0f,
+      };
+      vertex = mat4x4_mul_vec4(g_cam_matrix, vertex);
+      projected = project_vec4(vertex);
+      vertices[i] = vec3_to_vertex(projected);
+    }
+  }
+
   if (type == RENDER_TYPE_WIREFRAME) {
     Vertex v0, v1;
     u64 x0, y0, x1, y1;