Realflow alembic motionblur

[pechart]

Works great, thanks a lot. Your really saved my day. Week.

(But nevertheless it would be great if vlado or anyone else could say something about the alembic meshes with motionblur.)

[Dan Andersen]

Good news, happy it works =)

[pechart]

Thanks again. One thing is, that I can't simply retime the meshes anymore with the RF bin loader, like it was possible with the maya ABC loader. When I override the time attr on the realflowMeshSource with something like 'time1.outTime*3' the motionblur doesn't render anymore. I though this would happen because of the wrong trailing parts of the frame number while rendering, maybe.
When vray evaluates the motionblur on, let's say frame 100 it goes to 99.75 and 100.25. When I multiply this with 3 I have 99.75*3=299.25, which is obviously not correct. So I took only the first part of the outTime float, multiplied this by 3 and attached to unmodified .part to the new framenumber. Didn't work. So I have to render the whole sequence and retime in post or render each 3rd frame.

A nice thing is, that the (slight) deforming works.

So, again. My favorite option would be to just read in the ABC file and render that with motionblur.

[Dan Andersen]

Yes, you can't do that. Also, you can't have a duration of 1 or more.

The reason, as far as I can tell, is that the RF loader switches the file it loads right in the middle between frames (frame.5). So, say you render frame 100. When you use intervalCenter=0, and duration=0.5 (2 geometrySamples), it samples frame 9.75, 10.0 and 10.25. This means it's actually the same frame of the realflow cache that gets loaded for every substep, so no changing topology - just reading simple velocity values off the mesh. However, when you start retiming the cache or changing the duration/offset, you might render a frame where the bin loader switches frame on one of the substeps, and you get changing topology. This will fail (and VRay will warn you so).

I'm not sure converting it to alembic would make any difference, if the problem is inherent to rendering motionblur on changing topology.

There are nasty, hacky ways of making this 'work', but the cleanest way would be to do the retime in RF itself.

[pechart]

There are nasty, hacky ways of making this 'work', but the cleanest way would be to do the retime in RF itself, I think.

Yeah, that is the cleanest way. But getting the FX guys back to work after an approval is possibly as tricky as hacking a way around

[Dan Andersen]

Yeah, can't help you there. But the retime tool in RF is very simple and basic and has a preview function, so it's quite easy to work with. You could make a clean realflow scene, import the cached sequence into a bin loader, open the retime tool and fix it properly yourself

[pechart]

Yeah, good idea. I'll check that. Thanks again!