creating animation from scratch with CHOPS

[jonp]

I've been trying to abuse and use CHOPs for the first time, as much as possible, for a production I'm working on, mostly because of the knowledge that we have to render the whole thing now at 30fps and then repurpose it all later to render at 24fps. So I'm trying to time everything in seconds rather than frames, which CHOPs is suited for. The animation needs for this job are fairly straightforward, no character animation but a lot of long complicated camera work.

Unfortunately it feels like there are some inherent limitations to it, for one that I can't seem to find a way to create bezier curves or other types of animation curves without resorting to hacks like resampling a polyspline or sampling keyframed dummy objects.

Am I missing anything that would aid in this? The spline CHOP is only suited to modifying existing curves, and I don't see a way of creating beziers or cubic splines with a VOP CHOP.

Really underrated context in Houdini though... I've been impressed by how powerful they are, limitations aside. Instead of typo-prone unreadable hscript expressions you get a clear network of nodes that can do most of the same tasks.

-Jon

[edward]

The easiest way to do that is probably to use the Channel CHOP, which will simply evaluate the keyframe channel on its parameter into a CHOP channel. So you can use the usual keyframe editor (aka "Channel View" pane instead of "Motion View" pane).

[mightcouldb1]

Bam! Also worth mentioning that you can use the waveform chop or noise to do great things!

Edited July 16, 2013 by mightcouldb1

[old school]

If you are in to raw point sampling and can stand to lock the CHOP (fair game if this is way up the CHOP chain), you can use the raw channel edit tools at the bottom of the Motion View pane.

Hit "d" to turn on sample dots, then select some dots, and press one or more of the options at the bottom to sculpt the raw curves.

For example:

• start with a Constant CHOP set to a frame range (turn off Single Frame).
  
• Hit the "D" key in the motion view to turn on dots per sample
  
• Box select some of the dot samples (hitting "D" enables this feature)
  
• Click-Drag the selected dots up and down
  
• Hover over all the CHOP tool icons at the bottom. The tool tips are quite informative and tell you how these work with whatever you have selected on your channel.
  
• Select a part of the channel that has a sharp transition caused by your edit above.
  
• Press the "cubic" fourth blue icon from the left and your selection now has an ease curve to it.
  
• With the "cubic" button pressed down (the blue tools are active edit tools), make a different dot selection and then, depending on which dot you pick near the left, middle or near the right, you can drag this selection up and down with the "Cubic" filter remaining active. Modify the curve as though it were clay.
  
• Continue making more selections and dragging with the other blue icon tools to see what they do.
  
• Experiment with the other raw filter tools as well. Lots of fun and surprisingly quick. You can sculpt the exact curve shape you want quickly and easily without resorting to tons of keyframes.
  

It is common to modulate an incoming curve with a linear curve manipulated via the raw edit tools and then use a Math CHOP to either add or subtract the channels together. Keep things procedural as raw editing locks CHOPs.

It's fun to take an audio file at 44.1kHz and then up-sample to 120kHz and then start shaping the raw audio samples.

[jonp]

Thanks for the tips, I didn't realize before you could edit curves directly.

Still seems like there should be some functional equivalents to the curve modes when keyframing, though. Time for a RFE...