This shader simulates light scattered by a thin, uniform atmosphere. It produces shafts of light and volumetric shadows cast from geometric objects. It works with point, spot and area lights, but not with distant or sky lights. This is a scene-wide volume shader (or an atmosphere shader in Arnold terms).
The attributes are divided into two groups and are described in more detail in the pages below:
Remember that you must set Affect Volumetrics for each light that you want to use with volumetric scattering.
- Volume Scattering can be found in the 'Atmosphere' menu under Environment in the render settings window.
- Once 'Volume Scattering' has been enabled, it can be selected again by showing 'Dag Objects Only' in the Outliner window:
Volume scattering only works with 'local' lights that have a precise location and size, and inverse-square decay. It does not support lights at an infinite distance, such as the Ai Skydome light or the Directional light.
The example below demonstrates the effect of volume scattering through a medium. It consists of a polygon plane with a circular ramp texture connected to the opacity of an Ai Standard shader. The spotlight is pointing at the plane and 'Volume Scattering' is enabled.
Polygon plane with circular ramp texture connected to the opacity of an Ai Standard Shader
|An example scene can be downloaded here.|
Currently, 'Volume Scattering' does not compose well against volumes. This is because atmosphere's return a single flat result that is opacity mapped on top of whatever is in the background of the pixel.
Volume scattering effect cannot 'penetrate' through the cloud volume
Volumetric Scattering should be composited using an 'additive' mode such as 'screen' because volumetric scattering is light that cannot be represented in the alpha channel.
'Enable Matte' enabled for Standard shader assigned to wall geometry (left). Volume scatter render composited using 'screen' (right). Rollover images.