Surface materials mental ray attributes

 
 
 

The following section provides mental ray attributes that are shared between most materials.

mental ray

Irradiance

This is the ability to bounce indirect photons. Use this to map an incoming illumination map, such as one generated using Lighting/shading > Batch Bake (mental ray). For information about baking in general, see Baking illumination and color.

Irradiance Color

This is the color of bounced photons.

Scatter Radius

Determines how far light scatters under a surface. If the incoming light and the scatter radius are at an equal distance, mental ray assumes that all the light is absorbed by the material. The Scatter Radius attribute is in world space units, and has a default value of 0.

A value of 0 means that scattering is turned off. To set the other scatter attributes, the Scatter Radius must be set to a value greater than 0.

Scatter Attributes Rendered Image
Scattering is turned off, because the Scatter Radius value is 0.The material on the model appears solid, hard and flat.
 
Scatter Radius value is greater than 0, so scattering is turned on and you can adjust the other scattering attributes.The material on the model appears to have a glow beneath the surface, but still appears relatively solid.
 

With the Scatter Radius value set to 5, the effect spreads across the material.

The scattering in this image produces too much glow, indicating that the Scatter Radius value is too high.

 

With the Scatter Radius value set to 2.308, the material resembles a translucent milky plastic.

The scattering fades with the falloff of the light and glows along the shadowed edge.

Scattering is high in the mandible region because this part of the model is thin, allowing more light to be diffused.

 
Scatter Color

Determines the color of the scatter component of the shader. The default color is grey (0.5, 0.5, 0.5), which produces scatter that is the diffuse color of the surface. You can change the scatter color by using the slider, or map the attribute.

Scatter Accuracy

Determines how many samples from within the Scatter Radius are taken to blur the diffuse component of the shader. The default value is 97.

The higher the Scatter Accuracy, the more memory and time used for calculation.

Scatter Falloff

Determines how quickly light diminishes along the scatter path. You can set one of the following values:

Photon Attributes

Set attributes to Derive From Maya, or turn the option off and set remaining attributes, such as Specular Color and Diffuse, so that they are calculated using mental ray. Alternatively, you can change the settings in the Maya sections of the Attribute Editor (Common Material Attributes, and so on) and click Take Settings From Maya to compute the equivalent mental ray values for these attributes.