Valentine Kozin

Hopefully a quick and easy one for anyone that's used the FEM solvers more than I have.

Trying to add an FEM sim on top of an animation to capture deformation and soft-body collisions. However an issue I'm occasionally running into is a few of the tets getting caught inside the colliding geometry and stretching out to absurdity until they snap back. Image attached.

The collision geometry is a relatively complicated, but smooth, watertight mesh. I've tried increasing the FEM solver substeps all the way to 20, which hasn't had an effect on the issue and increasing the number of collision passes seems to have only made it worse.

Both objects have no friction, so there really should be minimal catching and pulling like this. What's the best way of going about avoiding this kind of thing?

That's brilliant, just the sort of solution I was after! Python nodes make it work just the way I want it to

So, these are a few fairly specific workflow questions that I'm hoping someone who has used Houdini in a game production longer than I have might be able to answer. The UE4 forum seems to be specific to uses of the Houdini Engine in UE4, whereas I am presently using it rather more straightforwardly for content authoring.

I would generally be quite happy export .obj files out of Houdini, except that they don't appear to store vertex colour data, or more than one UV set, so for more complex mesh set-ups I'm having to rely on FBX export.

One difficulty I'm finding is that while with .obj files it's possible to stick a File sop into your geo network and cache out multiple assets automatically, you can't do this with FBXes. It's possible to get File sops to output FBX files by writing in a .fbx extension, but this exports them with default FBX settings that are unreadable by UE4. I've been recommended to use a FilmboxFBX rop instead, which does work but I can't see a way to automate exporting multiple files.

E.g. If I set up a For Loop to run through a sequence of OBJs and process them, exporting a separate file on every iteration of the loop, or simply load, process and save a different file on every frame, this is something I can do by caching the OBJs with a File sop but it's not something I can find a way of doing with an FBX rop (best case scenario is it will output everything into a single .fbx with a geometry cache).

Is there a way to trigger an FBX render from within a geo network?

Secondly and even more crucially, I'd like to know if there is any way of exporting FBX files with multiple LOD meshes that UE4 would be able to interpret. It seems like it should be possible to achieve, given that there exist Simplygon plugins for Houdini that must somehow be capable of exporting LOD files. Yet I've not been able to find any workflow discussions that discuss setting up LODs in Houdini besides setting up subdivision detail levels for rendering, which is not quite the same thing.

I've tried loading FBXes exported from Maya with LODs set up, but Houdini does not seem to understand this structure and is therefore incapable of replicating it. It imports the LODs as separate geometries with no understanding of the LOD relationship between them, and does not seem to be able to export them back out as an FBX with LODs.