Rendering glass windows

[justa3Dman]

This ought to be simple, right? And yet....

I have found that V-Ray does not render glass with a clear alpha. If I knock down opacity, the entire thing disappears.

Hoes does one render a glass window for someone compositing in Nuke? I'll give an example.

I had to make a CG window pane in front of some blinds. When I hid the image plane, the glass' alpha was white.

It seems the only ways to get glass to composite over a background plate are

a) Render it with the image plane on, and perhaps provide a glass-isolating matte for the 2D guys, and

b) Render it alone, even sans-alpha, and use a Screen transfer mode in 2D.

Is this making sense? What am I doing wrong?

Thanks folks.

[SonyBoy]

This question isn't very clear. Can you post some images of what you're trying to do? However, there is often confusion surrounding alpha and refractions that's associated with the "Affect Channels" setting under the advanced refraction rollout. By default this is set to only color, so does not produce transparency in the alpha. Perhaps it's something to do with that....

Personally I think this feature has needed reworking for years as it's confusing as hell and is missing the ability to prevent transparency in passes where you normally don't want it.

[justa3Dman]

Actually, you might have answered my question. I'm going to look into that.

Thanks for taking the time!

[justa3Dman]

Okay... got a colored alpha. I guess it's because I tinted the glass green that its alpha is magenta-ish.

Obviously no refractive info is in this render... unless the AOV can provide that for the compositor?

[hermit.crab]

I guess it's because I tinted the glass green that its alpha is magenta-ish.

Yes.

unless the AOV can provide that for the compositor?

Yes, add a Refraction AOV.

[justa3Dman]

Okay, thank you both! I didn't think creating glass could be difficult, but I think I have enough now to get what I want.

Thanks folks!

[justa3Dman]

Yes.

I've never scene a colored alpha before. That threw me off. But, it makes sense since I gave the glass a slightly greenish hue.

Thanks again people.