Mental ray rendering

From TOI-Pedia

MIA Material

Mental Ray has a material shader that is optimized for architectural applications. It's recommended to use MIA materials when rendering with Mental Ray.

Detailed information: MIA Material

Physical Sun and Sky

Mental Ray has a Sun and Sky system for accurate indirect environment lighting. It can be set up with a single click.

Quick tutorial: Basic rendering with physical sky Detailed tutorial: MR Using the Physical Sun and Sky environment

Tone Mapping: MIA Exposure

When using any kind of physical lighting, you need to be able to make color corrections to the camera. Mental Ray offers the MIA Exposure control to do this. This is called exposure control. You could compare it to the settings on your photo camera that change how the camera handles the lighting conditions.

Detailed information: Tone Mapping

Render methods

Mental Ray offers various methods that can be used for rendering. Each method offers it's own unique features to the rendering palette available in Mental Ray. Some of these methods can be used 'standalone' or in combination with other methods.

In architectural applications, Final Gather is mostly used for exterior scenes or scenes that have a lot of light coming inside from outside (sun and sky).

Global Illumination is mostly used for interior scenes that are lit by artificial light sources.

Caustics are used when you need advanced refractive effects.

Mental Ray Nodes

Mental Ray Nodes shows an overview of a few interesting Mental Ray meterial, lighting and camera lens nodes.

Common problems

The option mental ray isn't listed in my Render Settings

Mental Ray requires a plugin to be loaded. Go to Windows » Settings/Preferences » Plug-in Manager.

Check Loaded for Mayatomr.mll. When you also check Auto load, the plug-in will be loaded automatically when you start Maya.

If you cannot find Mayatomr.mll probably you have not installed the mental ray plugin for Maya. Since Maya 2016 mental ray is not part of the Maya package. Download and install the appropriate mental ray plugin with your Maya version. E.g. Maya 2016 SP 3 needs mental ray for Maya 2016 SP3.

My mental ray tabs are different

Since Maya 2016 Autodesk made a major overhaul of the user interface. Fortunately, you can change it to legacy settings. Go to Windows » Settings/Preferences » Preferences and in the Categories panel select Rendering. Check the following two boxes: Show Maya Legacy Passes and Use Legacy Render Settings. You may need to reload Mayatomr.mll or restart Maya to make the changes effective.

My file textures look all washed out

MR gamma correction off.jpg
MR gamma correction on.jpg

This is probably due to incorrect gamma. When you're using exposure control in Mental Ray, your file textures are prone to get 'over-gamma-corrected'.

You can resolve this issue in several ways:

Enabling Color Management in Maya is the preferred method in recent versions of Maya. Wheter you're using Mental Ray with Tone mapping or not, enabling color management is always a good idea.

Alternatively, you can counter the gamma corrections for file textures with some tweaks to the Mental Ray Frame buffer and exposure control nodes. See Using mia_exposure_simple.

My render crashes with memory errors

  1. Optimize your scene (reduce polycount where possible)
  2. Optimize the Tessellation settings for scenes with NURBS surfaces or displacement
  3. Convert file textures to the .map format
  4. Optimize your BSP settings
  5. Use Batch Rendering to render your image.

If the memory errors persist, the scene may require a 64-bit version of Maya and a machine with lots of memory to render. Consider lowering the image resolution and render settings.

My NURBS geometry isn't rendered smoothly

When rendering, NURBS geometry is converted into polygons to allow it to be rendered. This proces is called tessellation. You can adjust the tessellation quality (smoothness). See the MR Rendering NURBS tutorial.

Mental Ray doesn't render sections using the camera clipping plane

  1. Make sure you didn't scale the camera (Modify > Reset Transformations or manually in the Channel box)
  2. In the Render Settings, mental ray tab: make sure Primary Renderer is set to Scanline (Using Raytracing as a primary renderer won't work)

Back to Maya

Back to Lighting and rendering

Personal tools