WARP CHOP tutorial available?

[raytheon]

hi all..

I'm trying to us a warp chop to vary the speed of an animation. Is there a good example file and/or tutorial about? I've got an old sidefx tutorial called "CHOPS - Motion Capture Data", but haven't found the corresponding bill_flip.hip.

Meanwhile i've created my own crude example, using a constant chop to feed in the warp curve. I can edit the curve by RMB and "Edit Data Channels..." (as done in the old tutorial), but it automatically locks the node. If i unlock it the curve data is lost. Assuming i'm doing this correctly, should i unlock the node or somehow save the data before unlocking it?

thanks

[edward]

Instead of locking, I'd suggest using a Channel CHOP instead and then keyframe the Value parameter.

[raytheon]

Thanks Edward! Can you tell me what the Channel CHOP buys you? Is it more efficient (it doesn't seem to be explicitly locking the node) or easier to maintain? I've tried incorporating it into my example but, although there is no error, the output in the Motion View does not seem correct when the Channel CHOP is enabled. Doubtless a simple mistake on my part.

My confusion arises from an assumption that the node lock/unlock is similar to pessimistic version control: lock, make changes, then commit to unlock the asset. From the help i understand that the node lock toggles a cache flag to allow Houdini to avoid recalculations when the network is cooked. Maybe it's just a convenient optimization that's on by default. When i attempt to unlock it the warning "This operation will discard locked changes" appears, which seems more like a version control warning. Perhaps i am alone in my confusion .

A good tutorial would be helpful if anyone knows of one.

[raytheon]

BTW this is the example file i'm using.

my_warp_eg.hipnc

[edward]

Thanks Edward! Can you tell me what the Channel CHOP buys you? Is it more efficient (it doesn't seem to be explicitly locking the node) or easier to maintain? I've tried incorporating it into my example but, although there is no error, the output in the Motion View does not seem correct when the Channel CHOP is enabled. Doubtless a simple mistake on my part.

I thought you wanted to avoid locking while editing your curves?

"Locking" in the Houdini node-sense just means that a copy of the data is now made and that the node will no longer cook since you have made custom overrides. So when you unlock, the node will recook and thus losing any special (non-procedural) edits that you made.

[raytheon]

I thought you wanted to avoid locking while editing your curves?

I'm pragmatic.. it just seemed like I might be misunderstanding something about locking. I think, with your help, that i understand what's going on.