how to create matte .

I rendered a clip in maya tga sequence with alpha channel but how can i render separate matte ?

What is the purpose of creating a matt when you already can render a clip with an alpha channel?

fine but i am watching here many up loader providing black & white mask channel .

It takes less work to create an alpha channel to be used as overlay than a clip with a matte.

P5 accepts and even encourages to submit clips with animation compression. I practically can't submit animation clips because of the size limitation (I think it is <500MB). So, I create and submit the rgb and then attach the alpha. Sure there is much more work for me and the buyer.

Zygis

hi zygis , how u create alpha to attach ? that's my question . i m newbie here.

I use Adobe AE and create rgb and alpha in one pass - just add another format when rendering.
I upload rgb and when clip appears in a keywording queue, at the right of the row there is an icon to attach some file. Click on that icon and then upload clip with alpha. After uploading the (1) appears on the right side of the row for that clip. Move mouse over that (1) and edit it.
Zygis

oops it means when i render any clip rgb+alpha channel ,no need to upload separate matte here. well thanks a lot , if i m making any mistake please inform me .great response ,
thank again.

Sure, if you'll render with rgb+alpha then no need to upload a separate matte. Bigger sizes of files with animation compression could limit such uploads. For my time-lapse growing plants clips with Photo Jpeg 99% quality the size of rgb clip could be ~500MB and alpha about ~100MB. But the size of animation clip is ~2GB.

Zygis