You can set the following preferences in the Rendering category of the Preferences window.
You can select your preferred renderer. This is the renderer that Maya resets to when you create a new scene (File > New Scene) or when you start Maya. This can be one of Maya Software, Maya Hardware, Maya Vector (if loaded), or mental ray (if loaded).
Select between 8-bit integer and 32-bit floating-point (HDR) image buffers in the Render View.
Select this option if you are using an output device that can display HDR color values, or if you want to apply color management inside the Render View window. For more information, see Displaying HDR images in the Render View.
This section only appears when the mental ray Mayatomr.mll plug-in is loaded (Window > Settings/Preferences > Plug-in Manager).
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.
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.
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.