diff -r 7c4a63a02632 -r 028798a72591 src/modeleditcontext.cpp
--- a/src/modeleditcontext.cpp	Mon Mar 09 22:12:50 2020 +0200
+++ b/src/modeleditcontext.cpp	Mon Mar 09 23:42:26 2020 +0200
@@ -63,27 +63,16 @@
 	return this->storedModel;
 }
 
-namespace
+static std::array<geom::Triangle, 2> splitTriangles(ldraw::Diagonal diagonal, const glm::vec3(&points)[4])
 {
-	using PropertyTriplet = std::tuple<ldraw::Property, ldraw::Property, ldraw::Property>;
-}
-
-static std::array<PropertyTriplet, 2> diagonalToPointProperties(ldraw::Diagonal diagonal)
-{
-	std::array<PropertyTriplet, 2> result;
+	std::array<geom::Triangle, 2> result;
 	switch (diagonal)
 	{
 	case ldraw::Diagonal::Diagonal_13:
-		result = {
-			std::make_tuple(ldraw::Property::Point1, ldraw::Property::Point2, ldraw::Property::Point3),
-			std::make_tuple(ldraw::Property::Point1, ldraw::Property::Point3, ldraw::Property::Point4)
-		};
+		result = {geom::Triangle{points[0], points[1], points[2]}, {points[0], points[2], points[3]}};
 		break;
 	case ldraw::Diagonal::Diagonal_24:
-		result = {
-			std::make_tuple(ldraw::Property::Point1, ldraw::Property::Point2, ldraw::Property::Point4),
-			std::make_tuple(ldraw::Property::Point2, ldraw::Property::Point3, ldraw::Property::Point4)
-		};
+		result = {geom::Triangle{points[0], points[1], points[3]}, {points[1], points[2], points[3]}};
 		break;
 	}
 	return result;
@@ -100,24 +89,13 @@
 	const ldraw::Quadrilateral* quadrilateral = editor.model().get(quadrilateral_id, &index);
 	if (quadrilateral != nullptr)
 	{
-		Q_ASSERT(index.isValid());
-		int position = index.row();
+		const ldraw::Color color = quadrilateral->colorIndex;
+		const std::array<geom::Triangle, 2> split = splitTriangles(splitType, quadrilateral->points);
+		const int position = index.row();
 		editor.remove(position);
-		std::vector<ldraw::triangleid_t> triangles;
-		triangles.reserve(2);
-		const std::array<PropertyTriplet, 2> split = diagonalToPointProperties(splitType);
-		for (const PropertyTriplet& properties : split)
-		{
-			const ldraw::triangleid_t triangle = editor.insert<ldraw::Triangle>(
-				position,
-				quadrilateral->getProperty(std::get<0>(properties)).value<glm::vec3>(),
-				quadrilateral->getProperty(std::get<1>(properties)).value<glm::vec3>(),
-				quadrilateral->getProperty(std::get<2>(properties)).value<glm::vec3>(),
-				ldraw::Color{quadrilateral->getProperty(ldraw::Property::Color).toInt()});
-			triangles.push_back(triangle);
-			position += 1;
-		}
-		result = {triangles[0], triangles[1]};
+		result = std::make_pair(
+			editor.insert<ldraw::Triangle>(position, split[0].points, color),
+			editor.insert<ldraw::Triangle>(position, split[1].points, color));
 	}
 	return result;
 }