Finalise implementing triangle clipping

include/rasteriser/rasteriser.h

@@ -8,10 +8,12 @@
 #include "vector/vec.h"
 #include "window/window.h"
 
+#define INVALID_VERTEX -1
+
 typedef struct {
-  u64 idx0;
-  u64 idx1;
-  u64 idx2;
+  i64 idx0;
+  i64 idx1;
+  i64 idx2;
   colour_t colour;
 } scene_triangle_t;
 
@@ -41,8 +43,6 @@ typedef struct {
   list_scene_triangle_t *triangles;
 } model_t;
 #define NULL_MODEL ((model_t){0})
-#define IS_NULL_MODEL(MODEL_PTR)                                               \
-  (MODEL_PTR->vertices == NULL && MODEL_PTR->triangles == NULL)
 
 typedef struct {
   f32 scale;
@@ -79,5 +79,6 @@ void draw_wireframe_triangle(window_t *wnd, Arena *arena, triangle_t triangle);
 void draw_filled_triangle(window_t *wnd, Arena *arena, triangle_t triangle);
 void draw_shaded_triangle(window_t *wnd, Arena *arena, triangle_t triangle);
 void draw_line(window_t *wnd, Arena *arena, line_t line, colour_t colour);
+bool is_null_model(const model_t *model);
 
 #endif // !RASTERISER_H