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.