This is a standalone script for computing a convex hull mesh from a scene element.
Run the script normally, e.g. by drag-and-drop into a 3ds Max session.
This will open a little UI to control the creation of the convex hull mesh. Pick a scene object, adjust parameters as needed (details in the tooltips) and click the calculate button to start the process. Afterwards, your convex hull mesh will be selected.
Note: This could be slow for high-resolution geometry.