I am currently running a simulation with the pyrofx and the first 25 frames or so of my sim run choppy like its simulating then the rest of it runs smooth like its already cooked. Even after letting it simulate multiple times it does this. Even if I write it to a file node it does this. Can anyone help me with this? Thanks in advance.

Hairston

Is realtime playback switched on?

Soothsayer
Is realtime playback switched on?

Yes I have toggled it both on and off. It does the same thing only faster or slower…its like the first 25 frames or so run like its solving (a stock fluid sim) then after that it runs very smooth. Another example is like the playback running the first 25 frames at 15 fps then the rest running at 60fps..its pretty strange.

The reason is most likely due to the amount of Cache Memory on the DOP Network Object. As the simulation cache increases and hits the limit, Houdini will start to write to disk thus causing the stuttering as it has to read from disk instead of memory.

You can try to increase the Cache Memory to 1000MB to see if it helps. Of course, this might slow your system down if you don't have enough RAM.

Hope that helps!

Cheers!
steven

Thank you for the reply Steve. I have 4gb so I could probably afford to do this. Now, when I render this out to a movie file will it run choppy like that or will it run smoothly? Thanks.

Hairston

I think I misunderstood your problem because if you're getting a choppy look when rendering it out, something else is wrong with your sim.

It's best to post the file or a render or a flipbook so we can look at it.

Cheers!
steven

Well basically whats happening is after it sims 125 frames, I then cap off the limit to 125 frames so it will run what is already simulated. Now, when I run that sim to see what it looks like completely solved, the first 25 frames or so run somewhat choppy and then the rest of the sim runs smoothly EVEN THOUGH the whole thing is completely calculated and sim'd. Does that help?

Thanks,

Hairston

In this case, it has to do with the Cache Memory parameter. Of course, you'll have to re-run your sim as soon as you change the parameter.

On the other hand, playing back in Houdini might be choppy but you can run out a flipbook which should confirm that the sim is not choppy.

Cheers!
steven

Thank you Steven, I will try this. Now I do see that this cache node is for particles. Will it work for fluids as well as this is a pyro simulation? Thank you.

I think he means adjusting the settings for your cache in the cache manager instead of the cache sop.
Windows -> Cache Manager

The parameter I'm referring to is found under the Simulation tab of the DOP Network Object itself.

Please see attached image.

Cheers!
steven

Thanks again Steven. I have tried changing that setting and it doesnt seem to help it any. I checked the amount of frames that it takes to get out of its “choppy” state and its around 67…the sim being a total of 198 frames. Im not sure what that could possibly be and im not sure on how to run the flipbook as I am still learning houdini.

Thanks

Flipbook is at the bottom right of the viewport pane. It captures screengrabs of the viewport, single or multiple frames.

If you right click the button you get the options. If you leave the variables $RFSTART and $RFEND, they will always use the start to the end frame of your timeslider, so if that changes you dont have to physically change the start and end frames for flipbooking. I always set the same variables in a mantra ROP when running animations.

Its like playblast in Maya.



Cheers