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Missing Alpha pass in MultiPass ProRender
Posted: 03 November 2018 02:12 AM   [ Ignore ]  
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I successfully created a sample project for a shadow catcher.  I only have Broadcast R20, so don’t have the special shadow catcher material.

In my scene of a plane and sphere on top the plane… the plane has a completely black material (non-PBR, color set to pure black). Added a compositing tag.  Set to ‘Shadow Catcher Alpha’ under ProRender section of the compositing tag’s attributes.

ProRender works a-ok; I have an Alpha pass.

But in a new scene, with what appears to be identical settings, I cannot see any Alpha pass in the multi-pass output.  I added all multi-pass options.

As a workaround, I copied the render settings from the working project and pasted into the non-working one.  Now it’s a-ok.

So how does one add an Alpha option to multi-pass?  I definitely did it somehow last week, but not remembering at all how I did it.  Thank you.

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Posted: 03 November 2018 02:18 AM   [ Ignore ]   [ # 1 ]  
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Hi Ricky Sharp,

Would you mind to (always) add a scene file? Here the one that worked and the one that doesn’t. Just the few elements that create the problem, no 3rd party material at all please. Thanks.
(If there is a problem with identifying the MIME type, etc, I’m happy to set up an upload link.)

Thanks

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Posted: 03 November 2018 02:35 AM   [ Ignore ]   [ # 2 ]  
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I will work on reducing a copy of both files to their bare minimum to reproduce the issue.  Thank you.

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Posted: 03 November 2018 03:09 AM   [ Ignore ]   [ # 3 ]  
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Ricky Sharp,

I guess the file below is the similar to the one that worked for you.

Scene file/screen shot
https://www.amazon.com/clouddrive/share/DlbMY2tZQ1bZ8o3JKxfgVcJe2fJN0XXXc1fs3LYvjAN

With reducing I had in mind, just to have the parts essential to the problem. In some cases the reduction helps already to locate the problem already. On the other hand, I get sometimes files with hundreds of objects, and then the search and sorting starts. As I have naturally not set up the file that I get, I have to learn every single part in it. It is a big help to get reduced files.

Please check the manual for limitations.
https://help.maxon.net/us/#MSHADOWCATCHER
https://help.maxon.net/us/#TCOMPOSITING-COMPOSITINGTAG_GROUPRPR

On the other hand, you can set Object Group IDs for the scene. This is like a combine Alpha. If you can have the colors R, G or B for the main interest objects, so each channel is a Alpha channel without a lot of work (i.e., keying.)
Scene file/screen capture
https://www.amazon.com/clouddrive/share/bNT9lU1StsGBIbiPjz4rmj0MScNweJ1RllVGsIysiAz
But yes, those ID channels do not have the same quality as a Straight Alpha for single objects would provide.

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 03 November 2018 06:35 AM   [ Ignore ]   [ # 4 ]  
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P.S.: here is a little screen-capture, to illustrate the process.

With more ID object colors, it might get more difficult to separate those. I would try to keep it first to R,G,B, and if more is needed to RG, GB, RB pairing. Besides RGB (white) anything esle is then keying and not combining channels anymore.

I have no idea what gamma your project is in. So I have left that as a variable.

https://www.amazon.com/clouddrive/share/2MV7CgkOLfuENs2OHvga8UhKaMiVmO4z7NhzuZnpchz

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
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Posted: 05 November 2018 08:18 AM   [ Ignore ]   [ # 5 ]  
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I saved out two render settings presets so I could help track down the issue.  The only differences I see between the two presets is on the Multi-Passes tab under ProRender.  I have Render Multi-Passes checked in both presets checked.  And every other checkbox is unchecked.  However, one preset shows the unchecked checkbox labels all in a bold font.  Whereas the other preset shows those same checkbox labels with a non-bold font.

I can also no longer reproduce the issue.  Both presets are allowing my ProRender renders to have a Alpha layer (as seen in the layers list of the Picture Viewer)

I suspect that perhaps something got corrupted somehow that has since worked itself out.

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Posted: 05 November 2018 10:30 AM   [ Ignore ]   [ # 6 ]  
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Hi Ricky Sharp,

Thanks for the update. If it is no produceable anymore, then I hope it stays that way.

If it comes back, please save the file and share it with the support. Fingers crossed it will stay away.

Let me know if there is anything else, I’m happy to look into it.

Fingers

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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