User Guide Reference

If the mesh light color texture is clearly visible in specular reflections you may need to increase the number of subdivision iterations for the mesh light. For example, this may be evident in a scene where a TV screen is reflected in a glass window.

It is generally recommended that you use Specular to control glossy specular reflections. The specular_roughness parameter of the Standard shader affects the blurryness of the specular reflections. In Arnold, this is called "glossy reflections", or also "specular reflections".

The Standard shader has a secondary layer of reflection, called simply "reflection", which is perfectly sharp and mirror-like.  It is only there for perfect mirrors or glass. Not for blurry effects. If you want blurry reflections only you should use Specular. The images below show specular reflections coming from a light source and mirror reflections coming from light reflecting off the surroundings.


The Sky Dome light will also not appear in reflections of the Standard shader. It is recommended to use Specular in combination with the Sky Dome light. If you want reflections to appear then you should use the Sky shader with 'Visible in Reflections' enabled.

Sub-Surface Scattering (SSS) simulates the effect of light entering an object and scattering beneath its surface. Not all light reflects from a surface. Some of it will penetrate below the surface of an illuminated object. There it will be absorbed by the material and scattered internally. Some of this scattered light will make its way back out of the surface and become visible to the camera. This is known as 'sub-surface scattering' or 'SSS'. SSS is necessary for the realistic rendering of materials such as marble, skin, leaves, wax and milk. The SSS component in this shader is calculated using a brute-force raytracing method.

You must ensure that the geometry normals are pointing in the correct direction, otherwise SSS will not render correctly.


SSS is important when replicating realistic materials such as plastics, for example:

This is a self-shadowing error that can result from low tessellation or when objects do not have thickness. It usually occurs in concave areas or when the light is behind the polygon mesh. In these situations it can introduce light leaking.

There are a number of workarounds:

  1. Increase the number of subdivided polygons (the artifacts will become smaller).
  2. Give the object some thickness so that it is not a single sheet of polygons.
Default AOV Group
"RGBA_default" is a beauty AOV that contains volumes if they are lit by lights not in any AOV light group, whereas "volume_default" should have volume illumination from lights not in an AOV group.

"Volume_default" + "volume_red" + "volume_blue" give the total volume pass, whereas "RGBA_default" + "RGBA_red" + "RGBA_blue" give the total RGBA beauty pass.

The green light is not in an AOV group



Only volumes are currently supported for per-light AOVs. Lighting from surfaces and the atmosphere will appear in the default light AOV.

A maximum of 8 different light AOVs are supported, although a given AOV can contain a bundle of any number of lights.




Velocity Scale

A scale factor for the velocity field. A value of 0 disables motion blur.


Velocity FPS

Sets the frames per second velocity value.



Velocity Shutter Start

Specifies the shutter open value at the current frame.


Velocity Shutter End

Specifies the shutter close value at the current frame.

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