remove junky UncoloredSpaceTriangle union, hide vertex generation from generic triangle implementation

src/rendering/twn_draw_c.h

@@ -83,32 +83,19 @@ typedef struct Primitive2D {
 } Primitive2D;
 
 /* union for in-place recalculation of texture coordinates */
-union UncoloredSpaceTriangle {
-    /* pending for sending, uvs are not final as texture atlases could update */
-    struct UncoloredSpaceTrianglePrimitive {
-        Vec3 v0;
-        Vec2 uv0; /* in pixels */
-        Vec3 v1;
-        Vec2 uv1; /* in pixels */
-        Vec3 v2;
-        Vec2 uv2; /* in pixels */
-    } primitive;
-
-    /* TODO: have it packed? */
-    /* structure that is passed in opengl vertex array */
-    struct UncoloredSpaceTrianglePayload {
-        Vec3 v0;
-        Vec2 uv0;
-        Vec3 v1;
-        Vec2 uv1;
-        Vec3 v2;
-        Vec2 uv2;
-    } payload;
-};
+/* needs to be later resolved in texture atlas */
+typedef struct UncoloredSpaceTriangle {
+    Vec3 v0;
+    Vec2 uv0; /* in pixels */
+    Vec3 v1;
+    Vec2 uv1; /* in pixels */
+    Vec3 v2;
+    Vec2 uv2; /* in pixels */
+} UncoloredSpaceTriangle;
 
 /* batch of primitives with overlapping properties */
 typedef struct MeshBatch {
-    uint8_t *primitives;
+    uint8_t *primitives; /* note: interpretation of it is arbitrary */
 } MeshBatch;
 
 /* TODO: use atlas id instead */