3D: Y-sorting

src/GPU3D.h

@@ -60,12 +60,12 @@ typedef struct
     bool IsShadowMask;
     bool IsShadow;
 
-    // data below rather specific to the software renderer
-
     u32 VTop, VBottom; // vertex indices
     s32 YTop, YBottom; // Y coords
     s32 XTop, XBottom; // associated X coords
 
+    u32 SortKey;
+
 } Polygon;
 
 extern u32 RenderDispCnt;