The Shadow CatcherThe Shadow Catcher can be used to create shadows cast by objects onto the surrounding background imagery. The shadows cast are not limited to simply a ground plane but can be cast onto other surfaces of varying shapes. option can be used to create shadows cast by objects onto the surrounding geometry. The shadows cast are not limited to simply a ground plane but can be cast onto other surfaces of varying shapes.
This feature is enabled by activating the Shadow catcher option on the Diffuse materialUsed for dull, non-reflecting materials or mesh emitters. applied to the shadow catching surfaces.
Figure 1: A Model is integrated into an image using the Shadow Catching material (image on the right).
In the render kernel window activate Alpha ChannelA greyscale image used to determine which areas of a texture map are opaque and which areas are transparent. and disable Keep Environment. When the image is rendered the shadows will appear over the transparent parts of the surface. This image can be used in a compositing package to merge the object and the shadows into the composition.