From: Filip Persson (
Date: Wed Sep 07 2011 - 08:30:33 CDT

Is it possible to draw the intersection volume (i.e the "overlap volume")
between two spheres in VMD? Could one use Boolean expressions to do this,
something like "draw sphere {x1 y1 z1} AND sphere {x2 y2 z2}"?

I also want the spheres to be centered on specific atoms in my trajectory -
how do I update the center position of a sphere in every frame? I tried

*set atomX [atomselect top "index X"] *
*set pos [$atomX get {x y z}]*
*draw sphere $pos radius 3 resolution 10*

for every new frame, but I get the error "need three numbers for a vector".

I really appreciate your help!