3 Replies Latest reply on Mar 12, 2018 4:46 PM by Chris Cunningham

Renderpasses + Glass material and transparency

A. B. Feb 13, 2018 4:49 PM

I am currently having some trouble with various renderpasses in my rendering process. I have a model that has a large glass sphere in it with other objects behind it. These objects however do not fill the entire sphere, and I want the rest of the sphere to be transparant in the output (Alpha + PNG). Now, for the Beauty pass, this works perfectly fine. But as soon as I add other passes such as Ambient Occlusion or any of the other render passes, the output files do not have transparency for the glass sphere.

I could of course disable the glass sphere for rendering all the other passes, but the sphere has a high IOR. This results in the passes not being refracted properly and not aligning up with the original render for compositing in Photoshop.

Does anyone have an idea how I could fix this while still keeping my render output file transparant? Or am I forced to render with a background?

Re: Renderpasses + Glass material and transparency

Nete Jakobsen Mar 12, 2018 5:45 AM (in response to A. B.)

I do unfortunately not know how you can fix this in Visualize, but I have another suggestion to make the sphere background transperent.

Maybe it could work if you add a non-used coloured item right behind your glass sphere as a "background" for the sphere. For example a very saturated magenta. When you then import the rendering intro Photoshop, you can go "Select" -> "Colour Range..." and then select the magenta colour, decide the fuzziness to fit the picture and either delete the colour or create a mask to cover it.

Let me know if you figured out how to fix it in Visualize.
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- Re: Renderpasses + Glass material and transparency
  
  Rob Rodríguez Mar 12, 2018 4:37 PM (in response to Nete Jakobsen)
  
  You should be able to take all your passes images into Photoshop and use the alpha channel to remove the transparent areas in the passes you want them removed in. If you are using the blend modes in Photoshop you may not need to remove the transparent areas in the passes because Photoshop will treat them as such with the blend mode.
  
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Re: Renderpasses + Glass material and transparency

Chris Cunningham Mar 12, 2018 4:46 PM (in response to A. B.)

Make sure to uncheck solid on the glass appearance and render with no background set to pure black and composite it all together in Photoshop.
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