PDG for whitewater sims

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30 posts
Joined: Jan. 2015
SORRY I posted this in the wrong place before. Apologies if it's already been answered:

Couple of questions:
I'm trying to use PDG and ROPS(TOPS) to streamline a whitewater fluid sim into my renderer.
First ROP - saving out the fluid sim works.

Second ROP which is connected to the first - reading that back in for Whitewater generation works, however the second ROP MULTIPLIES the amount of frames. e.g. I'm testing on 5 frames, the 2nd ROP starts running 25 frames.

Third ROPFetch which is connected to Redshift shows 25 frames of activity!

If I unconnected them, they no longer recognize dependencies. Is there a setting I'm missing so that each ROP knows to only act on the same set of frames?

2) For ROPS saving out a simulation -in the TOP node it seems like it's jumping around - randomly cooking say, frame 22, followed by 1, followed by 45, which seems odd. Shouldn't it cook sequentially as the sim works itself out?

Edited by morganv123 - March 22, 2019 09:22:11

Screen Shot 2019-03-22 at 7.57.57 AM.jpg (50.2 KB)

533 posts
Joined: May 2014
The second ROP Geometry node probably needs to be set to “Single Frame” instead of “Frame Range”. If it's set to single frame, it'll generate 1 work item per input work item. If it's set up frame range, it'll generate a range of work items for each item. This pattern is followed by most nodes - the TOP node will apply the operation defind by the parameters for each input work item.

If you're doing a simulation, you'll need to go to the ROP Fetch tab and turn on “All frames in one batch”, so they get submitted as a single job.
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Joined: Jan. 2015
Thank you. This worked out great. I'm still unsure of the logic:
The second ROP (Whitewater) is still a simulation so if I run all the TOPs at once, it follows 1, 2, 3 as the first ROP cooks and those frames become ready. However, if I just cook the first ROP and then cook the 2nd ROP it will jump about in sequence.

Anyway, it's very satisfying to see them all working right down to the render. Also noticed a huge reduction in memory use. This setup used to crash houdini before using ROPS, even with Cache simulations turned off.
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