I was wondering how one can cache to disk while checking the sim in the viewport.

With the "Vellum_io" SOP one can either use "save to disk" or "save to disk in background". But in neither situations I can actually see and check the simulation, I have to wait until it's done then load it from disk, which seems a bit weird to me.

Very often I'm trying different settings and play the sim in the viewport to check, so when a simulation is very slow, I first have to play it in the viewport, and then simulate it a second time to save it to disk.

I'd like save the playback to disk, and when it's ok, I'm done and replay it from disk.

How does one do that in Houdini ?

Thanks

You could use a File node instead. Place it in write mode and supply a filename. As you play the timeline, each frame will be written to disk. You'd need three in series to cache the three outputs from a vellum solver.

Generally, I hit the up arrow or flip book the viewport until I'm happy with the simulation, then cache it out.

normally sim is being cached to RAM so as long as you specify enough Cache Memory on your solver you can just play to cache and at any point play back the cached part and let it cache further
or tweak and play again etc, once happy just cache to disk afterwards, which will just write to disk from memory

this is pretty fast workflow as long as you have enough memory

you can always use File SOP in Write mode (or automatic) if you want to write to disk any input geo (sim or not) during playback or just when changing frames or any cook trigger
It's a bit dangerous though as you have to flip it to read or automatic once written to avoid overwriting by accident or if you keep it automatic you have to delete the files to be able to write again

overall, I always stick to memory cache as it's easy to tweak the settings and then just let it run in background or farm while still be able to check what's written out so far

Ah, thanks a lot.

The file SOP seems to do the trick. I was searching for a SOP named something with "Cache", silly me :-)