Overview
Before rendering the main image (or layers of images), the render engine may need to do a pre-pass to generate the needed shadow maps. The Shadows group of attributes controls the automation of that process (if needed). It also provide controls over what objects are casting shadows, wether these shadows are created using shadow maps or ray tracing.
The Shadows group
Shadow Linking
Specifies what objects are casting shadows from lights. It affects all types of shadows - depth map, deep maps and ray traced. included in a light's shadow map. It is possible to override its value on a per-light basis by using the Shadow Objects attribute of an assigned light attributes node (although sets must then be used to specify which objects are shadowed by the light; see Shadow Objects). The available options are:
| Option | Description |
|---|---|
| Use Light Links | Objects will cast shadows from the lights that are considered illuminating the objects by the light linker. This is the default. |
| Use Shadow Links _______________________ | Objects will cast shadows from the lights that are considered shadowing the objects by the light linker, allowing object-light relations for illumiation distinct from those for shadowing. |
| Ignore Light & Shadow Links | All visible objects will cast shadows from all lights. |
Auto-Generate Shadow Maps
Controls wether shadow maps should be automatically generated or not. Its default value is on.
Opacity Threshold
Only objects with opacities greater than or equal to the Opacity Threshold will appear in shadow maps. The default value is [0.0, 0.0, 0.0], which means that all objects will be included in the shadow map, even completely transparent ones. If this value is set to [1.0, 1.0, 1.0], only completely opaque objects will be rendered into shadow maps. Note that this parameter is only useful for depth shadow maps as deep shadow maps correctly handle semi-opaque surfaces. For users familiar with the RenderMan standard, this is the equivalent of the following RiOption:
Option "limits" "zthreshold" [r g b]