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Compositing Hardware Rendered Sprite Smoke...Not!

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Tim Kinnaird
Compositing Hardware Rendered Sprite Smoke...Not!
on Jun 1, 2009 at 3:51:38 pm

I'm not really a noob to Maya but I'm a noob to hardware rendering and it is giving me fits.

Maya 6.5
After Effects 5.0

I have created some black smoke (like from a steamboat stack) using maya particle sprites. With much tweaking I get something fairly close to what I'd like. Not great but acceptible.

The problem is that the hardware renders are coming out nothing like what I'm seeing in either the maya workspace or hardware test renders.

I'm a bit frustrated that maya uses my graphics card to render what I'm seeing in the workspace but for some reason takes a totally different approach when it batch renders. Counter intuitive?

Here is a link to some images that illustrates what I'm facing.

I'm using luminance to create the alpha because, apparently, my graphics card does not support hardware alpha.

Because there is a camera shake in the shot, I must use at least a 3 pass multipass so that I can also use motion blur.

In an effort to capture the subtleties of the opacity I tweaked my shader settings and bumped up the smoke much brighter while maintaining middle greys. I figured I could tweak later in After Effects and bring it to where I'd like it. No good.

No matter how I tweak the sprites, they turn into separate cotton balls at the tail of the smoke and blink out when their lifespan is up. Also the nice illusion of disappation created by the opacity ramp is lost in the renders.

Can anybody point me at some info on the net that might help?

Thanks for all your time and sorry so long!

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Michiel Duvekot
Re: Compositing Hardware Rendered Sprite Smoke...Not!
on Jun 2, 2009 at 4:03:04 am

If you want something that resembles what you see in the workspace, use the Hardware render buffer, not the Hardware renderer. They're different renderers and give vastly different results.


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Tim Kinnaird
Re: Compositing Hardware Rendered Sprite Smoke...Not!
on Jun 3, 2009 at 2:56:46 pm

Hi, Michiel. Thanks for helping. I wasn't very clear in describing my problem. All of these issues were coming up in the hardware render buffer.

I think I found out sort of what the problem is. The culprit appears to be the multipass. Even though a test render with multipass turned on takes longer to render and flashes while rendering as if creating the 3 or 2 "in between" renders, it still displays as a single frame render (which almost matches the workspace image). Maybe it needs the preceeding frame to exist before the multipass frame can be rendered as it will actually look? Not sure. This is a moot point for alot of reasons. To sum up: The lack in intuitive feedback makes trying to adjust my sprites un-workable. A useable frame of my sprites is deep in the scene and I can't afford to allow the particle sprites to grind to that spot repeatedly to adjust my variables and do actual renders. So I'll have to find another solution.

I rendered the smoke layer with multipass turned off and the results were much closer to what I saw in the workspace.

So...for now I have rendered out my smoke without multipass. I think I stumbled across something about being able to export my camera move to After Effects and have it motion blur a layer on that info. I'll try to track that info down and see if I can take care of my problem in AE. If you or anybody reading this knows where I can find any of that on the net, please let me know.

Thanks again for your help. :)

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