volume_scattering

Class

Shader

Output

RGB

Synopsis


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).

 


 

density
Increases/decreases the atmospheric volume density. The following images show the effect of altering the 'Density' setting.


samples
The samples are distributed according to the volume density. More samples will refine the quality of the solution.


eccentricity

Henyey-Greenstein Anisotropy coefficient between -1 (full back-scatter) and 1 (full forward-scatter). Default is 0 for an isotropic medium, which scatters the light evenly in all directions, giving a uniform effect. Positive values bias the scattering effect forwards, in the direction of the light, while negative values bias the scattering backwards, toward the light. Changing the eccentricity therefore means that you will get a different effect depending on whether the camera is looking toward the light or away from the light. 

Note that values very close to 1.0 (above 0.95) or -1.0 (below -0.95) will produce scattering that is so directional that it will not be very visible from most angles (and what scattering you do see may be noisy), so such values are not recommended.

attenuation

The attenuation parameter sets the rate at which the rays of light traveling through the scattering medium are extinguished and how much light coming from the background is blocked. A high value means that light will only travel a short distance through the volume, while a low value means that light will travel a long distance through the volume.

affect_camera
Controls the degree to which volume scattering affects camera rays.


affect_diffuse

Controls the degree to which volume scattering affects diffuse GI rays. 

affect_reflection
Controls the degree to which volume scattering affects reflection / glossy rays.


rgb_density

The density control is multiplied by this RGB value (so a blue value here means blue light is scattered). 

It is also possible to map textures to this parameter in order to get interesting volumetric effects. The example below uses a 3d fractal texture to simulate a cloudy fog effect.

Fractal texture mapped to Color

rgb_attenuation
The attenuation control is multiplied by this RGB value (so a red value here means red light is attenuated).


 

example_renders

 

Further examples

 

 

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