Just came with this idea for a shadow matte o shadow catcher.
1.- First render your scene as usual (i use an hdri and a crane model i’m working on).
2.- Assign a default white material to all geometries that needs to catch shadows ( in my case… just a plane).
3.- In Corona render settings assign a material override with a black corona material to all scene assets except the geometries you want to catch shadows.
4.- Add a CShading_shadows render element. As i noticed, ou can compose the “inverted” shadow pass (Ctrl+i with the layer selected in photoshop) later in “multiply mode” over the beauty pass.
Just came with this idea for a shadow matte o shadow catcher.
1.- First render your scene as usual (i use an hdri and a crane model i’m working on).
2.- Assign a default white material to all geometries that needs to catch shadows ( in my case… just a plane).
3.- In Corona render settings assign a material override with a black corona material to all scene assets except the geometries you want to catch shadows.
4.- Add a CShading_shadows render element. As i noticed, you can compose the “inverted” shadow pass (Ctrl+i with the layer selected in photoshop) later in “multiply mode” over the beauty pass.
nice I will try it tomorrow 
but would be nice to have away without rendering 2 times, the state editor can be pain in the …
