I remember there being a tutorial where insert was used to put something on the side of a camper, and I swear they used illumination modeling to have the insert match the changing lighting…I cant seem to find that feature? Is it gone?
Currently there isn’t illumination modelling for the Insert module, but you can render the cutout and then use blend modes in your compositor.
If you specifically want to capture the subtle lighting you can do an insert via the Remove module, which is what you may be referring to.
This is where you do a classic Remove procedure using a clean plate, and then instead of painting OUT something in the clean plate, you paint IN something to the clean plate.
In your camper example, if you wanted to insert a graphic, you would track the side of the camper as normal, duplicate the layer and then create a clean plate on the frame you want to insert the sign. Then in Photoshop, paint in the sign onto the clean plate and then use that as your remove.
You can then use the illumination modelling as normal.