“mappend” associates additional command line operations with a particular movie frame. These “generalized movie commands” will be executed every time the numbered frame is played.
mappend frame: command
frame = integer: the frame to modify
command = literal command-line text
mappend 1: hide everything; show sticks mappend 60: hide sticks; show spheres mappend 120: hide spheres; show surface
The “mset” command must first be used to define the movie before “mdo” statements will have any effect. Redefinition of the movie clears any existing movie commands specified with mdo or mappend.