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View Full Version : sprite alpha anti-aliasing

j00ey
09-20-2003, 02:25 AM
hi all

i'm rendering some sprites which are using a sequence of files [with alpha] and i can't seem to get them to generate an clean + accurately anti-aliased alpha in the final render. to be honest i haven't checked the alpha channel itself, but when i comp it in after effects i get aliasing artifacts which i then have to choke off. [i'm not at work now so can't check it].

i did a workaround by rendering against a colour similar to most of the image they'll be comped onto, but in the docs it says if you're going to comp the sprites, render against black.

i'm sure though that there is a way to get a decent alpha output in the first place though, otherwise it would be pretty useless.

also i noticed that on an nvidia card [not sure which but generally very good and specifically maya-compliant] i was using earlier i didn't get alpha at all, but with a matrox g400 [which is generally pretty sh!+e with maya] i get the half assed alpha.

any ideas anyone?

thanks
j00ey
gmask
09-24-2003, 08:57 PM
Specifically which card are you using?

This is the output from the hardware renderer that you are talking about correct?

What settings did you using in the hardware options?

You probably need to turn on the oversampling feature to smooth things out.
j00ey
09-25-2003, 02:11 PM
thanks for the reply gmask

i sorted it out eventually. i think [if i remember correctly] that the nvidia card didn't give me alpha when renedring as TGA, but then i rendered the sequence on the matroz as TIFFs and got the alpha, though i still had to choke it in post.

not sure which the nvidia card is, not there at the moment.

i tried rendering against an image plane of the pre-rendered scene which it was to be comped onto, and the geometry that the sprites had to go behing in there with 'use background' shader and geometry mask on, but i couldn't get the image plane to be transparent to alpha. i just wanted the unwanted edge to at least have the same colour values as the background... but in the end i just choked it off.

you can see the final render here...

http://www.cgtalk.com/showthread.php?s=&threadid=89988

comments welcome

j00ey
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