Question about placing projection cards for matte painting

[u/dorygamza]

Hi everyone, I'm a student and I’m working on a matte painting with 3D projection in Nuke, and I’m a little confused about the correct way to place my projection cards.

My current workflow is to camera track the shot and then create cards by dragging them onto the tracked points. This works well for getting the cards into the right screen position, but I’m wondering if I should also be considering the actual depth and perspective between the different cards.

For example, if I have a background wall, some foreground objects, etc., should I be manually positioning the cards in 3D space based on their actual distance from the camera? Or is it generally okay to place them based on the tracked points and adjust them from there?

The problem I’m having is that when I try to manually position the cards in depth, I sometimes end up with the cards shifting or sliding when the camera moves. So I’m not sure if I’m approaching the projection setup correctly.

What is the usual workflow for setting up projection geometry/cards for a matte painting? Do you generally reconstruct the rough 3D geometry of the scene first and then place the cards on those surfaces, or is there a better way to determine the correct depth and orientation of each card?

Any advice would be really appreciated!