some refactoring

hopefully improved rendering speed
added support to add .obj obstacles

mapview/2D/MV2DElementStair.h

@@ -95,6 +95,18 @@ public:
 		std::vector<Floorplan::StairPart> parts = stair->getParts();
 		std::vector<Floorplan::Quad3> quads = Floorplan::getQuads(parts, floor);
 
+		// skip drawing?
+		BBox2 bbox;
+		for (const Floorplan::Quad3& q : quads) {
+			bbox.add(q.p1.xy());
+			bbox.add(q.p2.xy());
+			bbox.add(q.p3.xy());
+			bbox.add(q.p4.xy());
+		}
+		if (!p.isVisible(bbox)) {
+			return;
+		}
+
 		for (int i = 0; i < (int) parts.size(); ++i) {
 
 			const Floorplan::StairPart& part = parts[i];