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charleyc
03-31-2007, 08:11 PM
A discussion on this was forming in another thread of a totally different topic, so I am breaking it from there to here to get others input :)

The discussion is on the fact that, besides the Scanline renderer, using Object Motion Blur (OMB), spin gets ignored in the MB. Mental Ray does not take it into account, VRay, however, does. A work around is to use Mesher on the particle system and you can get Image Motion Blur (IMB) to work with the scanline or to generate a Velocity pass to run through a compositor.

Hi Charley,

Yeah, I reported it a few months back.

I'll take a look at using a post motion blur with the velocity channel from the mesher object.

VRay is a bit of strange one - I just did a test now with a superspray scene I used for some water tests

This is the scene rendered in scanline with OMB

http://www.stephendgreen.pwp.blueyonder.co.uk/water_spray.wmv (http://www.stephen.d.green@blueyonder.co.uk/water_spray.wmv)

(Edit - I put the wrong URL in originally, so the link doesn't work unless you copy and paste it into your browser for some reason)

Which uses quickly rotating cubes to give a nice blobby feel, (and IMB can't really handle that), but memory becomes a concern quite quickly (hence looking at other renderers)

When rendered through Vray, it complains about changing mesh topology and doesn't 3D motion blur at all - however Pflow does seem to handle it OK.

Last time I tried it I was on RC2, maybe RC3 has more compatibility across the particle systems. (The reason I wasn't using PFlow for this is that I got better performance generating spray from deforming meshes with simple legacy particles)


Cheers,

Steve


Steve

I am not sure why VRay gave you that error. I have been able to use it as long as it has supported PFlow velocities correctly (I beleive it was the first 1.5 build I got). I am familiar with that trick, but depending on how close you get to the water, you could probably come up with a much quicker solution. I have done a number of water jets like that, but they are usually seen from a distance of 8' or more. You are never right on top of them. I use the scanline to render them and get render times of a few seconds a frame.

www.charleycarlat.com/Tests/WaterFountains.mov (http://www.charleycarlat.com/Tests/WaterFountains.mov)

Anyway, I would be curious to see your results.

Steve Green
04-01-2007, 07:14 PM
No problem,

I think PFlow itself is OK with Vray, it's the legacy particles that throw up an error (PArray for example)

The main reason for not using PFlow on this is that I find it a lot slower with deforming meshes than PArray, so for water splashes like whitecaps PArray seems a lot more responsive.

I'm away from my PC at the moment, but I'll post any more tests I do.

Cheers,


Steve

charleyc
04-01-2007, 10:35 PM
Hmm. I never noticed that VRay doesn't support legacy particles and MBlur. I suppose I don't use them enough to notice. RC3 doesn't work either.

PsychoSilence
04-01-2007, 11:43 PM
thatīs very important to know!
thank you charley for sharing that info.

BTW thatīs a great fountain you made!!! post the flow/settings please ;)

kind regards

anselm

thev
04-02-2007, 08:04 AM
V-Ray is only able to extract accurate motion blur information from Particle Flow. Even if it did work with standard particles, it would only be able to derive the translational movement, and not particle rotation, because of the limited information that standard particle systems provide.

Best regards,
Vlado

charleyc
04-02-2007, 08:16 AM
V-Ray is only able to extract accurate motion blur information from Particle Flow. Even if it did work with standard particles, it would only be able to derive the translational movement, and not particle rotation, because of the limited information that standard particle systems provide.

Best regards,
Vlado

That too is good to know. Thanks Vlado.


Here is a scene of the skinnier water fountain that I had done. The larger one is very similar. BTW, if you have Box3 (purchased through Orbaz) and can access v1.06, the new Keep Apart update makes these very fast.

www.charleycarlat.com/Tests/WaterFountain.zip (http://www.charleycarlat.com/Tests/WaterFountain.zip)
R9 version

One of the Events was to simulate a bit of mist...it is not in the rendered version I posted, and it can slow things down.

Steve Green
04-03-2007, 09:32 AM
Hi,

(back at my machine now)

Nice fountain.

It's a shame that VRay can't get the rotational information for the motion blur on legacy particles (I'm not sure why the scanline OMB can though).

I don't use them that much - It really was just in certain cases that it seemed a lot faster in PArray than PFlow.

Box#3's on my list, though.

Cheers,

Steve

thev
04-03-2007, 11:01 AM
It's a shame that VRay can't get the rotational information for the motion blur on legacy particles (I'm not sure why the scanline OMB can though).Well, OMB (similar to camera multipass motion blur) just takes several snapshots of the mesh at different times without a smooth transition between them - it does not attempt to derive anything special from the particles. To achieve the same thing with V-Ray, you can override the motion blur geometric samples of the particle mesh (from the V-Ray object properties page) to a larger number (e.g. 5 or 10). This will cause V-Ray to essentially do the same as OMB - it will render several snapshots of the particles at different times, if it cannot make a smooth transition between them. Camera multipass motion blur will also work, although it will probably be slower, of course.

Best regards,
Vlado

Steve Green
04-03-2007, 11:16 AM
OK, cool - got it working (for translation anyway).

Thanks,

Steve

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