I have set up a camera projection of a street with buildings. Problem is the photo is way too grainy and my CG car looks too clean. So I need to match the grain on the car to the photo I'm using for the camera projection. I have added film grain using a downloaded overlay before to CG scenes. But now I need to add only to the CG car and possibly its shadow and not the whole scene. How would I do that in Blender? In the compositor? I could easily do that in Fusion, but that would mean rendering different passes from Blender and adding to the render time too. If I can output it directly and finished from Blender, it would be better.

I have tried following some tutorials where they use the Compositing tab, but they are all focused on adding grain to the whole render/scene. I see that my only input option for the Render Layer node in the compositor is Scene. I can’t choose the car there, which I had thought would be the way. But I only need to add grain to the car and possibly its shadow, which is done via a shadow catcher.

I'm totally new to the compositing tab. Have some basic experience with the shading tab.

Thanks for the help.


1 Answer 1


This could be done using ID masks inside Compositor Related video on youtube Id Masks (tho it's old I'll add a couple of screenshots where specific settings are located)

Compositor setup: Use color socket in the mix node to plug in your grain

Enable object index and material index before Rendering inside Propertied Tab > View Layer > Passes > Data

Configure the pass index for each object

Or for material if you want
enter image description here

Now, inside the compositor, under your id mask, configure the index you specified for material or object

Index MA - material pass index, OB - object

And another note: you will need to rerender in order to use new configurations


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