diff -r 6988973515d2 -r ca23936b455b src/ldrawalgorithm.h
--- a/src/ldrawalgorithm.h	Wed May 25 20:36:34 2022 +0300
+++ b/src/ldrawalgorithm.h	Mon Jun 06 22:01:22 2022 +0300
@@ -1,5 +1,6 @@
 #pragma once
-#include "modeleditor.h"
+#include "main.h"
+#include "model.h"
 
 namespace ldraw
 {
@@ -10,15 +11,13 @@
 		Diagonal_24
 	};
 
-	// Splits the specified quadrilateral into triangles.
-	// If it is not a quadrilateral then no action is performed
-	auto splitQuadrilateral(ModelEditor& editor,
-		quadrilateralid_t quadrilateral_id,
-		Diagonal splitType = Diagonal::Diagonal_13
-	) -> std::optional<std::pair<triangleid_t, triangleid_t>>;
+	std::pair<Triangle, Triangle> splitTriangles(
+		const Quadrilateral& q,
+		ldraw::Diagonal diagonal);
 
-	void invert(ModelEditor& editor, ldraw::id_t id, GetPolygonsContext *context);
+	/*
 	void makeUnofficial(ModelEditor &editor);
+	*/
 
 	template<typename Fn>
 	void circle(int segments, int divisions, Fn&& fn)
@@ -34,3 +33,5 @@
 		}
 	}
 }
+
+ModelElement inverted(const ModelElement &element);