Vray+ MAX - how to do post work on objects located behind glass/reflections?

[nickdk]

Hello everyone

 

I'm making an interior shot where I look out through a window onto a concrete wall. I would like to do post work on the exterior concrete, but i'm not sure since I don't want to ruin the rendered glass that is in the "way".

Should I use render passes for this work flow? I'm a bit confused

 

I'm using Vray and Max

[trino]

In your glass material you can activate the "affect alpha" option in the refraction parameters, that will give you an alpha image with transparency in the glass area. Hope that helps.

[BrianKitts]

yes, a reflection render element would allow you to fix the wall then replace the glass on top of your "fix"

[Craig Ramsay]

This is how I would do it -

 

Step 1 - Render the scene out with a reflection pass, refraction pass and a multimatte for the concrete wall and glass.

Step 2 - Open the original render then layer the refraction pass on top using the multimatte to mask out everything but the glass on the refraction layer. This should look like you have removed all the reflections from your glass.

Step 3 - Now use the multimatte again to select the concrete wall and make the adjustments that you wanted to it.

Step 4 - Once all that is done, you need to layer your reflection pass on top, again using multumatte to mask out everything but the glass.

Step 5 - The last thing you need to do is set your reflection layer to screen mode (I think, I'm not at my workstation so it could be multiply). That should do the trick.

 

There could be other ways to do it but it's late and that's the first method that came to my mind. Hope it helps Oh, and this method is for Photoshop/After Effects, the workflow would be a bit different if you are using a node based compositer like Nuke or Composite.

[nickdk]

Thank you so much for helping me! I'll try the different methods later today - And Craig, thank you for taking the time to write such a detailed recipe, that's very nice of you