Mental Ray Preferences

Select Windows > Settings/Preferences > Preferences > Rendering to set the following preferences.

Mental Ray Preferences

Use Maya-style alpha detection on file textures

If a file texture is mapped to the transparency attribute of a shader, and there is no alpha channel in the texture, then, if you render with mental ray, your final rendered image will contain no transparency. This behavior is unlike that of the Maya Software Renderer, which, when there is no alpha present, calculates the luminance in lieu of transparency. If you are using the mental ray for Maya renderer, and you would like to use luminance as your alpha channel, enable this option.

Note:

Enable this attribute for backwards compatibility.
Disable this attribute if you are using render targets. See Previewing your composite in the Render View for more information.
This is a global setting and affects all file textures in the scene. In order to control the alpha for each texture, enable Alpha is Luminance under the Color Balance section of the file node in the Attribute Editor.

Delete history on render proxy updates

Select this option to delete the construction history when you update your render proxy file.

Note: When this option is enabled, all construction history for the node is deleted. This includes the transformGeometry nodes that are created when your render proxy is updated, as well as any construction history on your placeholder object, for example, a polySplit node or a polyExtrudeFace node.

Enable ray-tracing for shaderball swatches

Select this option to enable raytracing for mental ray materials shaderball swatches.

The reflection and refraction environment is a raytraced checkerboard so that you can identify different values for refraction and reflection, as well as predict the final rendered result.

While updating, the shaderball swatch displays a red outline to indicate it is currently rendering.

If you have more than one editor open in Maya, the rendering priority of queued swatches is as follows:

Attribute Editor
Hypershade
Node Editor

Note: This feature is only applicable to mental ray shaders.

Use optimized textures (auto-conversion)

Enable this option to convert textures in your scene to an optimized format (.map) to increase rendering efficiency. This feature converts all textures referenced in the Maya scene to an optimized file as a pre-render process. The original textures are substituted with the new tileable files during the render process. The file texture nodes in the scene remain untouched and still use the original textures such as bmp and tga. This feature is off by default.

Optimized textures location

By default, the textures are stored in the cache at sourceimages/cache in the current project directory. However, you can also choose to save textures to a custom location.

Note: The conversion process only occurs once for each scene file, unless the time and date of the source image has changed, in which case, the conversion process occurs again.

Custom Location

You can add the <scene> flag to append the scene name to your directory path or file name. This field also supports environment variables.

For example, if you have an environment variable $MYCACHE=C:\mycache, then $MYCACHE/<scene> causes Maya to expand both $MYCACHE and <scene> to create the custom location. If the expanded customer location does not exist, Maya automatically creates it.

Conversion Mode

Select between two modes: converting only assigned textures or all textures. Only assigned textures are texture nodes which are connected to a shading network that is assigned to at least one object in the scene.

Update optimized cache textures now

In most cases, conversion to optimized format occurs at render time. However, if there are a large number of files, or, if you are working with a render farm, then you can convert all textures at once by using the Update optimized cache textures now button.

Important: The set local flag for textures is ON when using optimized textures. Therefore, if you are using standalone or satellite rendering, converted images must be accessible from every machine. For best performance, it is recommended that you copy the images to every machine.