worked on 3d models within map

adjusted grid factory
adjusted nav mesh factory
minoor changes/fixes
new helper classes
refactoring

grid/factory/v2/Helper.h

@@ -44,6 +44,19 @@ struct HelperPoly {
 		bbox_cm.add(p.xy());
 	}
 
+
+	void shrink(float cm) {
+		Point2 center;
+		for (const Point2 pt : points_cm) {center += pt;}
+		center /= points_cm.size();
+		for (Point2& pt : points_cm) {
+			Point2 dir = pt - center;
+			float len = dir.length();
+			dir = dir.normalized();
+			pt = center + dir * (len-cm);
+		}
+	}
+
 	/** does the polygon contain the given point (in cm)? */
 	bool contains(const Point2 p_cm) const {