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emitting fluid from fast moving object - need help


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I've got some difficulties making a scene work, so I'm looking for some inspirational advice.


There is some animated geometry that's moving relatively fast, approx 400 - 500 km/h (~300 mph), the geo is originally coming from an Alembic and was animated in Maya. There is no chance the animation will be reworked.


I attached a piece of geometry onto it and turned that into an emitter (via Fluid Source SOP) for a Pyro Solver and I attached a TimeBlend SOP under the ABC in order to work against the frame-by-frame stepping.


However, all I got were some individual smoke puffs at the places where my emitter had been the frame before (besides, I tried the setup also in Maya, it was more or less the same results for this part). Increasing Substeps on the DOPNet didn't really help. This is what I got:




So I used the Scalar Volume > Motion Blur in my Fluid Source SOP, which helped at least a bit:





This, I channel referenced into the trail SOP you can see in the picture right before my Fluid Source, I referenced the Frames to Blur into the Trail's Trail Length/ Cache Size at it was suggested here:




...this smeard my emission. So far so good.


The problem is now that my emitter doesn't emit just individual smoke puffs, anymore the fluid itself doesn't work for me. If I emit from a static emitter into the very same container, the fluid behavior is turbulent and it spreads quickly with nice, rolling movement. But with the emitter moving, all I get is a boring stick with jagged edges, it takes a couple of frames until forces and turbulence seem to kick in. I tried increasing turbulence, even to slightly nuts values, but I couldnt' get anything but that boring stick sort of look.




So I was wondering if any of you guys has an idea what to do here, or give me some input how you'd handle that situation.


The camera is static, so is there a sensible way to slow down the animation coming from the Alembics and then somehow speed up the fluid caches, e.g. simulating at 100fps (target speed is 25 fps)? Is there maybe something I'm bitterly missing?


Thanks for any hints or suggestions!!







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If you want to slow down your animation throw down a time blend followed by a time warp and you can scale up the frame range of the animation.


A different way to do this is to use is to use a time blend after the animated geometry and to increase the substeps on the dopnet.  Personally when I am doing fast moving objects I like to emit particles first from the animated object then I emit smoke from from the particles.  By doing this I find I can get away with less substeps as the particles tend to fill in the gaps.


If you need more, I would increase the motion blur on the Fluid Source node (under scalar volumes).

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