How to light a scene that also has a projection mapped gobo?

[kalibahlu]

I have a comp of a scene built in AE 2023 that has an image projected to line up with the final frame of an animation. The effect is working well, except that I cannot add an other lights to the scene without the new lights also projecting the image from a different directions.  Is there a way to assign the projected image to just one light and then be able to add other lights withouth them projecting the image also?  I tried precomping the scene comp with continuous rasterization/collalse transformations, but then it still projects from added light.  Does anyone know the solution?  Thank you!

[Mylenium · Accepted solution]

No. AE doesn't have light inclusion/ exclusion. You have to solve your conundrum by restructuring your comps or using other tricks.

Mylenium 

[kalibahlu]

Thank you, Mylenium!  I'll see what I can come up with. I'm trying precomping the other way, with the gobo in the top level comp and the other lighting in the precomp. Maybe that will work.  Hard to believe that if you use a gobo, that's the only light you can have, but it might be that way. Any suggestions welcome!

[kalibahlu]

Well, that didn't work either, because "Accepts lights" has to be on for the regular lights and off for gobos, so there's no way.  So I'll use two comps, one comp with the room lighting and one with the gobo, and composite them together.  Thank you for your quick answer, Mylenium, I appreciate your expertise, as always!

[Rick Gerard · Accepted solution]

You have to duplicate the camera and the light used for the projection, pre-compose the shadow catcher, the Gobo image (the image you are projecting), the duplicate light, and the duplicate camera then put it on top of the original background layer and do not collapse transformations. Now you have your projection, and you can light the other 3D layers in the scene. 

[kalibahlu]

Thank you, Rick!  In this case I'd have to use a few different precomps layered up since I have objects in front of and behind the shadow catcher objects, and I'd have to composite in the lighting on the shadow catcher objects to get it to match the rest of the scene.  In the end, I ended up precomposing each shadow catcher object separately and using the projection map as a guide for placing an instance of the image in the right place in each comp, then turning off the projection map.  But your suggestion is a logical way to work around the problem, and I might go that way for the other parts of this project.