Bryan Ray

NMVHS
Is it possible to have a looped animation built in an asset with component builder, e.g. a waving flag or burning tree?
I'm experimenting this with putting value clip in component builder, doesn't seem to work.

I'm sure you've either solved this by now or given up, but I needed to do this very thing this week, so I've worked it out, and I present this solution for the benefit of those who come behind.

The Geometry Clip Sequence LOP creates "value clips," which are the typical way you'd make an animation loop. Consult the docs for that LOP for full details. I'll just give the procedure and brief explanations here.

To use Geometry Clip Sequence inside a Component Builder requires a couple of tweaks. First, since you're not getting the geometry directly from the Component Geometry node any more, go to the Component Output and change the Source to "Input Primitives." Otherwise, the composition arc created by Geometry Clip Sequence will prevent Component Output from being able to use it.

Place a Geometry Clip Sequence LOP and connect the output of Component Material to input2. Append a Cache LOP after Geometry Clip Sequence, and the output of Cache goes to Component Output.



In Geometry Clip Sequence:
Set Primitive Path to /ASSET
Tick "Get Geometry From Second Input"
Change the Manifest File Save Path and Topology File Save Paths to match the Component Output's Location.
You could, of course, use an expression to drive this. For example:

• $HIP/usd/assets/`chs("../componentoutput1/name")`/manifest.usd
  
• $HIP/usd/assets/`chs("../componentoutput1/name")`/topology.usd
  

This is a little fragile since you have to manage the name of Component Output to ensure these files don't go to the wrong place. It'll typically update as desired if you change the node name, but it's not terribly difficult to break the link.

Change Clip Primitive Path to /ASSET
If you want your asset animation to loop, tick End Frame and enter the end frame of the animation.

In the Cache LOP:
Set Cache Behavior to "Always Cache All Frames."
Delete the channels on Start/End/Inc, and in the End field, enter a value larger than the longest clip you will ever need for this asset. It's a good idea to set the Update Mode to Manual before doing this, as it will cook every frame specified, which could take some time.

The presence of the Geometry Clip Sequence will break whatever internal mechanism sets the path for the materials, so between the Component Material and Geometry Clip Sequence nodes, add a Configure Layer LOP. Tick "Save Path" and enter an appropriate path for the material.usd file. Again, you can use the same kind of expression as above:
$HIP/usd/assets/`chs("../componentoutput1/name")`/materials.usd

dragonyhr66

shen25748
Hi, thank you for your reply!

I used the launcher to install everything, Houdini 19.5.493 itself and also the plugin. I noticed that it first checks the $HFS variable in the code so I manually added the path to environment variable and it is able to load the plugin now. So somehow the paths I put in the houdini engine preference are not recogonized.

Hello could you be more specific how to modify this??

It's been a while, but since I just ran into the same issue, I thought I'd answer for the benefit of those who come later. You need to edit the file maya.env, which is described here: https://help.autodesk.com/view/MAYAUL/2024/ENU/?guid=GUID-8EFB1AC1-ED7D-4099-9EEE-624097872C04 [help.autodesk.com]

Mine was completely empty, so I just added the line, as described by Bobcat:
HFS = D:\Production\SideFX\Houdini 20.0.625

That's obviously the path to my Houdini install—you'd change it to wherever yours is. Once I'd made that change, Maya loaded the plug-in without complaint.

Ah, I see. I should probably defer to the folks who understand USD at a lower level than I do. Although responses may be slow this week due to an event in London.