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First of thanks for taking a look at my question.

The problem

Please take a look at the following gif:

issue_gif

Instead of using a grass texture I made the grass transparent since the background video already had grass in it. This way the whole thing would match nicely in the final composite.

In the cliff on the left you can see the shadow of the backfaces moving through the transparent grass. To counter this I made the backfaces transparent with the following node setup:

node_setup

However, now you can see the frontface of the object trough the transparent backface.

Question

How can I hide/not render the parts of the mesh that are behind the transparent material/grass?

EDIT (further explanation)

Gif:

image

2 is the top of the cliff you can see in the first gif. '2' is partially transparent so it matches nicely with the plate (vid).

1 is the backface of the rock that you can see moving in the first gif. I want this to not be visible trough '2'. Making '1' transparent doesn't work, neither does changeing the transparency passes. Since 1 transparency pass will just show the back face again..

Wijnand M
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  • It is hard to understand what you are doing with the current information. Please use the [edit] link at the bottom of your question (https://i.stack.imgur.com/lXFuK.png) and add more information and images that help us understand your project. Is suspect that the issue you are having is related to the transparent bounces, but I can't say for sure. –  Jan 15 '18 at 16:23
  • Maybe related: Black artifacts when looking through many transparent objects? or Transparent textured planes produce black artifacts –  Jan 15 '18 at 16:24
  • Hey @cegaton thanks for your interest. I added onto my question. I hope it's enough for you to understand what I'm dealing with. If not, please let me know. – Wijnand M Jan 15 '18 at 16:44
  • I would try to prevent the awkward transparency from occurring there to begin with, not try to patch it afterward. I have a feeling that means modeling some grass. If you use colors/textures from the grass in the source video it should match nicely. – Mentalist Jan 15 '18 at 16:55
  • I did try that, it looks a lot better with the grass from the video poking trough (this ofcourse is entirely dependent on my skills on modeling the grass). If I can't find a way of hiding the backface of the rock I'll resort to adding some extra rocks on top to hide the clipping. But i'd prefer a solution ofcourse. – Wijnand M Jan 15 '18 at 17:21
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    I still do not understand the issue completely or where the grass and rock play into this... but maybe what you are trying to do is not so much a backfacing issue but something that has to be done with masks in the compositor. –  Jan 15 '18 at 17:54

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