Vray Alpha help

[nick2730]

Hey guys, I need some input. I cannot figure out why this is happening. I have a simple redline here that will animate in a 180 degree arc that i will overlay in premier ontop on the standstill image i have. I picked random screens from the arc to show whats going on.

 

I set everything in environment to alpha 0 and matte material using vray properties. Then the object to an alpha on 1. Everything renders fine, i select to save as png with alpha In the view port it shows both the image and alpha to be correct, yet when i view it the color of the bar which is suppose to be solid red is half red with a black line almost like a shadow in it. I cannot figure this out

Edited October 27, 2010 by nick2730

[nick2730]

After comparing i understand why i think. its because the alpha mask is bigger then the object, but why is that?

[Stephen Thomas]

I set everything in environment to alpha 0 and matte material using vray properties. Then the object to an alpha on 1.

What do you mean? There doesn't apppear to be anything in your environment. If you have a plane or something then the alpha could well be picking up the shadow cast by the red line as well as the line itself. Also, I'm not sure if PNGs use pre-multiplied alphas or not, but you should maybe put the image you are going to use as the background in your environment slot to avoid getting black fringing too.

 

Do you have after effects? You could probably do this in about 30 seconds without having to use max at all.

[nick2730]

What do you mean? There doesn't apppear to be anything in your environment. If you have a plane or something then the alpha could well be picking up the shadow cast by the red line as well as the line itself. Also, I'm not sure if PNGs use pre-multiplied alphas or not, but you should maybe put the image you are going to use as the background in your environment slot to avoid getting black fringing too.

 

Do you have after effects? You could probably do this in about 30 seconds without having to use max at all.

 

I do have after effects, but am incredibly stupid with it, I tried searching for how to. All i want in an arch animated in 180 degree angle lol. ive used after effects only a handful of time. Any help where to look?

Edited October 28, 2010 by nick2730

[Flint]

Set your background to green. Forget the alpha channel and edit it in premier.

 

http://www.digitalvideofuel.com/greenscreeninprem.htm

Edited November 9, 2010 by Flint