This page provides information on the Corona Shadow Catcher Material, its settings and usage.
Overview
The Shadow Catcher Material allows you to composite 3D geometry onto a background image (a.k.a. plate) whilst preserving the shadows and reflections (if turned on). Also, you can create an infinite background for your product visualization images.
Settings
Matte/Shadow
Enviro/Backplate – The backplate for compositing - a real-world photo.
Projection mode – How to handle projection for secondary (reflected) rays that hit the material. This generally needs to be set to correspond with the backplate projection (simple backplate or 360° enviro map) to get correct reflections of the shadow catcher on the scene object.
Alpha mode – How the shadow catcher is displayed in the alpha channel.
Using the For compositing option also makes the shadow catcher black for direct rays, which is required for correct workflow.
When Alpha Mode is set to For compositing, directly visible color of Shadow catcher material is overridden to black. To compose the render correctly, make sure to override directly visible environment color to black as well.
Shadow amount – How much light is bounced off the shadow catcher onto other objects (a relative value). Increasing the value forces less light bouncing, therefore making shadows darker.
Reflection Properties
Level – Defines how strong the reflection is.
Color – Allows choosing the color of the reflection.
Use matte projection mode – When enabled, all maps use the camera projection specified by Projection mode above. When disabled, only the Enviro/Backplate slot uses it and others are not projected.
Fresnel IOR – Index of refraction (IOR) for Fresnel reflections - controls the amount of material reflection in a physically plausible way. Higher values create stronger reflection. Set this to 999 to disable the fresnel effect (i.e. to create a mirror-like material).
Glossiness – Controls how sharp or blurred the reflection is. A value of 1 gives completely sharp reflections, while a value of 0 gives completely blurred reflections.
Bump – Defines the bump level.
Project Backplate Option
Use enviro for off-screen rays – Use scene environment for off-view rays when using simple backplate.
Off-screen color – Use this map for off-view rays when using simple backplate.
