HDRI Lightgroup/linking

Question

Let's say I have an object with a backdrop. That backdrop is covering up scene details that I want to be reflected in the model. How can I allow the model to receive the reflections of the HDRI background that the backdrop is covering up, yet still render the backdrop behind it?

Answer 1 · 2025-03-25T23:42:26Z

replied Tuesday at 11:42pm

My first thought is to use view layers and then. Combine them in the compositor

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Answer 2 · 2025-03-26T12:18:49Z

Omar Domenech replied Wednesday at 12:18pm

I agree with Dwayne, render them separately and combine them in compositing.

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Answer 3 · 2025-03-26T12:36:20Z

Martin Bergwerf replied Wednesday at 12:36pm

Hi Sid,

You could also use a Mix Shader for that Backdrop and Mix a Transparent Shader in Slot A with your normal Shader in Slot B and use a Light Path Node and connect the Is Camera Ray to the Fac of the Mix Shader.

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Answer 4 · 2025-03-27T03:27:06Z

s

replied Thursday at 3:27am

Okay, so I don't understand anything anyone is sayings so far, but I'm guessing this is a compositor thing? Do I create light groups first or what do I do?

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Answer 5 · 2025-03-27T06:27:36Z

Martin Bergwerf replied Thursday at 6:27am

Hi Sid, my computer wasn't working properly yesterday, but this is what I meant:

Light Path.png

In comparison, without the Light Path Node:

Light Path_00.png

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Answer 6 · 2025-03-27T12:18:44Z

Omar Domenech replied Thursday at 12:18pm

Marti's approach is great. But to your question, yes, in the compositor or even in Photoshop. You render the elements separately with alpha and combine them in compositing at the end.

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