From: Raik Gruenberg (
Date: Mon Dec 11 2000 - 10:40:13 CST


I use VMD 1.5 to visualize AMBER MD trajectories. I wanted VMD to update
the secondary structure representation (cartoon) during an animation.
Unfortunately, neither of the two variants described in the manual seem to

OK, here are some more details:
I first tried the 4-line method
(proc structure_trace ...
trace variable vmd_frame w structure_trace).

Then I sourced in and used the sscache methods from the documentation - no
success. After calling start_sscache the method sscache is indeed called
whenever the frame changes but three things are strange:

1) it never enters the
>if [info exists sscache_data($index,$frame)] { ...
part, even if the frame was visited before
2) yet, it never seems to get to the last return statement
3) the variable sscache_data doesn't seem to exist anyway.
info exists sscache
always yields 0

Any suggestions?
Thanks a lot!

Raik Gruenberg | EMBL
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Tel: +49/62 21/38 72 96 | Germany