Welcom in the forum Katew!
Hm... AutoCAD works with lines, surfaces, solids. Like in the real life only the solids have a mass. So you will need to draw solids in order to calculate the center of gravity. What is your "project"? How did you draw it? If you have a closed contour you can try to convert it to a REGION and find out that the MASSPROP works on regions.Originally Posted by katew
I wrote once a Lisp routine to calculate the centroid of a mesh see here