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 skylights. 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.
- The shader can be found in the Create menu in the Material Manager window:
- Once you have created the material, drag it onto the 'Atomsphere' attribute in the Environment section of the 'Main' Arnold Renderer settings.
Atmospheric scattering only works withthat have a precise location and size, and inverse-square decay. It does not support lights at an infinite distance, such as the Skydome light or the Distant light. Also emissive materials (e.g. standard with Emission enabled) are not supported.
The example below demonstrates the effect of atmospheric scattering through a medium. It consists of a polygon plane with a circular ramp texture connected to the opacity of a Standard shader. The spotlight is pointing at the plane and an 'Atmospheric Scattering' material has been created and connected to the 'Atmosphere' attribute.
Polygon plane with circular ramp texture connected to the opacity of a Standard Shader
Currently, 'Atmospheric 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.
Atmospheric 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). Atmospheric scatter render composited using 'screen' (right). Rollover images.
Further examples of Atmospheric Scattering