Background transparency

[David]

Hello,

 

Can anyone tell me if its possible to render an object in VIZ against a transparent backgound (so that you could open it in Photoshop and it would appear as a layer, with the Photoshop checkered background layer showing up behind it?)

 

At the moment I'm rendering against a black background, and then using the magic wand tool to delete the black in PS - very tedious.

 

I'd be very grateful if anyone could help with this subject!

[Tim Nelson]

What you do is save your images with an Alpha Channel. Then when you open your image in photoshop, go to the Select menu, then "load selection." I think the channel is called Alpha 1. It will select everything but the background, so you can then cut and paste everything onto a new layer.

 

hope thats what you're after

[STRAT]

if you render against a black backround in viz then save as a tiff for example, the alpha channel is freely available automatically to you in photoshop. no need to magic wand it urself.

 

in photoshop look at the layer's channels, and you'll see it pre-masked in there already

[David]

Thanks for the replies guys!

 

What I'm looking to do is render out a building that has a lot of glazing, and in some places you can see right through the building and out the other side.

 

I don't yet have a background image (site photograph), but need to get on and knock out the renders anyway. I'm looking for a way to do this so that the reflections on the glazing will still be apparent, but without any background at all in VIZ ... I want to comp the background in behind the reflective glazing in PS later. (So I'm looking for something like a matte/shadow material but for reflections!)

 

Is this possible using alpha channels? (I'm ashamed to admit I don't know much about alpha channels in PS!)

[Tim Nelson]

David,

 

What you just described is entirely possible using your alpha channel. If your glass material is transparent, you can still place objects behind it in photoshop and keep the reflections in front. I would suggest setting up a background environment in viz though to get a close approximation of what you are going to need. It doesn't have to be a solid color background for it to work, like you are doing. The alpha channel will still save the same no matter what background is there.