CGTalk - Maya Sprite Smoke

knight_2k

02-28-2003, 06:18 AM

Hi everyone.. I'm having a Hell of a time getting my maya Hardware rendered smoke to look good on a composited background.. I've looked at the footage and the problem seems to stem from mayas inability to mix the alpha channels of the sprites in an additive fassion, as they lay over top of eachother.. Which in turn gives me a verry flat smoke when composited over an image.

Does anyone have any Solutions in Hardware Renderring stage or sprte or compisiting stage...??

I'd appreciate anything.. Thank you.

jussing

02-28-2003, 11:39 AM

I know this is no optimal solution, but how about rendering the smoke again, with a perfect white material (100% self illuminated) on black background, and use that as a premultiplied alpha in your compositing package? :shrug:

Cheers,
- jonas

Norb

02-28-2003, 12:15 PM

have you turned on depth sorting for the sprites?

mattwood

02-28-2003, 01:30 PM

It's a well known and very old bug. You have to do what jussing says.

knight_2k

03-01-2003, 01:48 AM

KO Thanks guys, I'll Give it a try.. I think I have to recreate the smoke images with their alpha channels and a bright white image For their new colour.. Rendering the smoke with just a white shader gives me lots of squares.. Well in anycase.. I'll try it now and Send you anotehr post with an update.. Thanks again.

Ali.

jussing

03-01-2003, 09:16 AM

Hm... hadn't thought about that, but now that you mention it, we should have seen it coming...

Exactly what is your image source?

It seems to me like you shold be able to somehow automatically "just" transfer the alpha data to the color data, and then render the smoke with that, instead of manually recreating it. (?)

Ie, if you image source is a movie file, run it through After Effects once, where you composite a solid white color through the clip's alpha, and then export that to a video file of same resolution 'n' all, as your original clip.

Then import that to your smoke setup, and render. That should give you a perfect alpha channel for your smoke animation.

Good luck,
- jonas

mattwood

03-01-2003, 01:11 PM

Actually its a lot simpler than all that - you don't have to alter your source image sequence. In your original file texture node set the colour gain to black and the colour offset to white. Also adjust the diffuse value on the material if necessary - I usually have to turn it up to 3 to get a proper white.

knight_2k

03-01-2003, 05:44 PM

Hey Thanks Guys... Mattwood I can't believe I actually said I was going to redoo the sprites.. lol, It was kinda late.. I actually ended up doing exactly what you said. Using that technique and Animating MAsks in post... I got the look I wanted.

Thanks to everyone..

Ali.

On another note.. Where is a good refrence for Getting sprites. for smoke. Are blobby sprites better, Realworld I guess would be the best.

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