In the image below you can see a cube, a shadow catcher that is under the cube (Looks like a grey plain), and a red plain under the shadow catcher.
Right now the shadow catcher is catching the shadow, but everywhere that isn't a shadow, it shows the colour of the world background.
I want it to show the shadow, and then show the red plain underneath where it isn't catching the shadow.
Here is an example with an HDRI:
As you can see, the shadow catcher correctly catches the shadow, but it doesn't show the red plane underneath. I would like it to catch the shadow, and display whatever is underneath it.
I am using cycles with GPU, shadow catcher is ticked on the upper plane.