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

Tom Nixon ignivomous at gmail.com
Wed May 25 09:56:48 EDT 2011

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

My workflow for adding expressions is generally to left click on the
parameter to toggle the expression. Change the type to python, and then
right click Expression->Edit Expression. I'm sure the order of those steps
occasionally has been mixed up. I was just able to reproduce the error by
creating a second keyframe manually, and then editing the expression. I
really don't think I do this by accident, but I suppose it is possible that
I have absent mindedly.

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?


On Wed, May 25, 2011 at 2:25 PM, Edward Lam <edward at sidefx.com> wrote:

> On 25/05/2011 1:54 AM, Tom Nixon wrote:
>> I think that the keyframes have always been the first frame of a given
>> scene. So it would appear that I was doing dev work in a scene that
>> started
>> on frame 1 and then frame 17. Eventually I would find that my expression
>> has
>> been saved as two separate keyframes on each start frame. I am not able to
>> reproduce this simply by changing the start frame, though. Lately, almost
>> all of my expressions have been python, but I'm pretty sure that I've had
>> this happen with hscript expressions too.
> What type of parameters have you been experiencing the problems on?
> For hscript expressions, the workflow is typically:
>  - If it's a non-string parm, then just type your expression directly.
>    A key gets created for the expression at frame 1.
>  - If it's a string parm, then type the expression directly, using
>    backticks.
> If this is the workflow, I think it's pretty hard to accidentally create
> extraneous keys. For the Python expression workflow, it's required to
> manually create a key first on string parms so that might explain the
> accidental creation of extra keys.
> -Edward
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