[Sidefx-houdini-list] two keyframed expressions on a single parameter

Edward Lam edward at sidefx.com
Wed May 25 11:58:42 EDT 2011

On 25/05/2011 9:56 AM, Tom Nixon wrote:
> I just found a node in my scene that this has happened on. This is a string
> parameter with a python expression on it. In this case it is a delete CHOP
> with the scope being set by an expression. I'm pretty sure I've had this
> happen in float parameters as well. I will send you the file separately

Actually, if your global animation frame range starts at 17, then I 
think then the expression key gets created at that frame. ie. it 
corresponds to $FSTART in the scene. So I thought we might be able to 
reproduce this in a new scene by editing the expression with different 
values of $FSTART via changing the global animation frame range. 
Unfortunately, this didn't reproduce the problem.

If you're editing the expression inside an HDA in a scene file with 
different global animation frame start times, then that might explain 
it. You perform some sort of expression editing action that thinks you 
need a key at $FSTART and creates it for you. However, I don't know what 
that action is.

> It only bites me every so often, but I now just have a script that searches
> for double keyframed expressions. Do you think it would be worthwhile to
> only allow one keyframe in a parameter when it is an expression?

Unfortunately , we don't have any distinction what is an "expression" vs 
a "keyframe". They are one and the same in Houdini. "bezier()" is just 
another expression. Ditto for "bezier() + 1", etc. Rather than trying to 
make the distinction, I would rather we found out what's causing the 
extra keyframes and fix that. Thus far, there doesn't anything wrong 
with your workflow that should create those extra keys.


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