Hello. I am not too familiar with setting up Engine OTLs, but I am having a go at creating an interactive ripple solver for a character interacting with a water surface. Yesterday, I discovered the limitation of Engine that on Maya's side, the Trail SOP cannot calculate velocity, since Maya is pushing each frame individually.

I have since implemented the Cache SOP as a work around, but now I find that the Ripple Solver will not generate any output in Maya. If I bypass the ripple dopnet, the OTL returns the correct deformed geometry that I'm using as an animated rest for the solver.

Does the ripple solver fail for the same reason as the Trail SOP - due to Maya only seeing single frame snapshots of what the engine is doing? I would be quite surprised if HEngine cannot handle any integrated DOP networks.

good question. I have the same question

Yes, it's a limitation of the plugin architecture that houdini can only access the current frame data of an input geometry object. So you'd need to either provide the re-timed animation as multiple inputs on the Maya side, or cache the inputs (either on the maya side or in houdini). Is it possible to attach a copy of the RippleSolver asset too see what's happening with the cache?

Not the answer you are looking for, but maya has a pretty good ripple solver its the pond

I will let Duncan know that the pond ripple solver still has fans :-) I see you did not recommend Bifrost though. It's good to get feedback about where the engine plugin is providing the most value in Maya, and where we could do better.