Shadow catcher not working when camera aiming upwards

[it_refplus]

I've posted this problem before, and I still have this issue. The shadow catcher is not working when the camera is aiming upwards. As soon as I aim it downwards, it works fine. Any idea how to work around this problem ?

[deyan.hadzhiev]

Hi it_refplus, can you send an example scene with the simplified setup you are trying to achieve? The matte surfaces have no limitation regarding the relative rotation of the camera and the matte surface, so I suppose this is either a bug or there is something missing in your setup.

[it_refplus]

Here's a simple file that shows the problem. You can render with both cameras and see the difference. With the ceiling camera, the shadow is not rendered.

[deyan.hadzhiev]

After inspecting the scene - it seems that the problem is the orientation of the actual shadow catching plane. The matte shadow surface is considered only for objects oriented towards the camera (with normals facing the camera). The plane used as a shadow catcher ("Ceiling") in your scene, is facing away from the camera (it has its normal vector not facing the camera).

Since this is the intended behavior of matte surfaces, here are several options to achieve your desired effect:
1. You can use objects which have volume and are not single surfaces, for example a very thin Cube object.
2. You can rotate the Plane around its X or Z axis by 180°.
3. You can change the orientation of the Plane object to -Y (maybe the simplest solution):

[it_refplus]

Thanks so much! Should have thought of that.