OctaneRender® improves realism by implementing the Shadow Catcher to create shadows cast by objects onto its surroundings (Figure 1). The shadows cast are not limited to simply a ground plane, but can be cast onto walls and other objects in the scene that represent objects in the 2D environment map.


Shadow Catcher with HDRI Background

Figure 1 : Shadows appear in the transparent parts of the image where the shadow catcher objects were placed 


To use the Shadow Catcher:

    1. Make sure there is a light source in the scene. This can be a direct light source, or an emission map connected to a scene object.
    2. Add the Shadow Catcher material to the shadow catching objects in the scene
    3. Alternatively, a Diffuse or Universal material can be placed on the shadow catching objects in the scene and enable the Shadow Catcher option at the bottom of the material parameters.
    4. In the Kernel Settings, activate Alpha Channel and make sure Keep Environment is disabled.

Shadow Catcher Parameters

Enabled - The material is transparent unless there is some direct shadow cast onto the material, which makes it less transparent depending on the shadow strength.

Opacity - Controls the transparency of the shadows via a greyscale information.

Custom AOV - Writes a mask to the specified custom AOV.

Custom AOV Channel - Determines whether the custom AOV is written to a specific color channel (R, G, or B) or to all the color channels.