Using MDL with mental ray for Maya 2016

In Maya 2016 we are introducing basic support for loading and rendering MDL materials with mental ray. In this post we want to take a closer look at how these materials can be used in Maya. For a general introduction to MDL in mental ray, check out this post.

The MDL Node

In Maya, MDL materials are represented by a new surface shader node called mdl_material, which is located in the mental ray surface material section of the “Create Material” window or “Hypershade”.

Create MDL material node

When you assign an mdl_material to an object, you will see that it contains two drop down lists: One for choosing an MDL module and another one for choosing an MDL material:

mdl-material-property-view

An MDL module is a file which can contain one or more MDL materials and has a “.mdl” extension. By default, mental ray for Maya 2016 ships only one module, that contains the default_material, a light grey diffuse. Because of that, both drop down lists contain just one entry.

To populate the lists you will need more materials. In the next section, we will see how to get some.

Adding MDL materials

As already announced in the MDL introduction post, example materials can be downloaded here.

1) Unzip the archive to a temporary directory.

By default, mental ray for Maya uses one root directory for placing MDL modules, the directory shaders/mdl within your mentalrayForMaya2016 installation.

2) Copy the folder mdl_examples_for_maya_3dsmax into the MDL root directory as shown below:

mdl-directory

If you do not have write permissions in the Program Files directory or would generally prefer another location, you can define additional MDL root directories by specifying the MI_MDL_PATH. To do so, open the Maya.env file, which can be found in the Maya 2016 user directory:

maya-env

Add the line

MI_MDL_PATH=<Path to MDL files>

If you, for example, make an MDL root directory called “mdl” in your Maya/2016 user directory, as shown in the screenshot above, your MI_MDL_PATH path needs to look like

MI_MDL_PATH=C:\users\<USERNAME>\Documents\Maya\2016\mdl

More than one path can be specified, separated by a “;”.

A note on packages

In most cases, MDL modules are organized into packages, just like our example package. On disk, a package corresponds to a directory. The name of the package is the name of the directory. Packages can be nested to organize complex libraries. Within a package, modules can reference each other and contained resources (like textures) relative to each other or the package root directory. Because of this, it is important to always retain the package structure. Never just copy single mdl files or subdirectories out of a package into your MDL root directory, always use the full package, including the root folder.

Rendering MDL materials with mental ray for Maya

Now that our example package has been put into place, start Maya. Create an object and assign a mdl_material to it. The MDL Module drop down list should look like this:

Example PackageWhen you choose a module, the material drop down list will be populated with the materials contained in the selected module, and the first material will automatically be selected. The “MDL Material Parameters” section shows the parameters of that material, which you can modify to your liking.

mdl-with-render

Other MDL materials, focused on requirements from the automotive industry are available for download in the Advanced Rendering Forum.

Limitations

MDL materials are closed entities. They cannot be used in a shading network. Even though Maya allows connections to traditional shader and utility nodes, mental ray will ignore these  connections. However, MDL materials can be used alongside with traditional materials and shaders.

In its initial state, the mdl_material node does not come with a swatch render, has no viewport representation and is also not supposed to work with IPR. These limitations will be removed in future releases.

16 thoughts on “Using MDL with mental ray for Maya 2016

  1. bgawboy says:

    The latest version 3.13 of mental ray just came out with Maya 2016. It has many new features, two major ones in a new GI algorithm and support for MDL. Of course, the MDL is completely new, and we will be adding more and more. In particular, I am planning a mila to MDL conversion utility, so you could take advantage of the mila UI for layering.

  2. rachyd says:

    Yes I know that, but I am asking for Mentalray STANDALONE “GUI”.
    Why mrStandalone has no Graphical user Interface like Maxwell?
    I think a lot of artist prefer to use GUI rather than typing a lot of commands to render a simple scene or a big scene!
    If you attempt to build GUI for mrStandalone that’s awsome, and all will be happy…and a lot of studio & artist return back to use mrStandalone!
    That’s what I think

    1. Standalone is designed for scalability and rendering on a server farm where a GUI doesn’t mean anything and actions are scripted across 100s (or 1000s) of nodes. Artists don’t log into nodes on a renderfarm to run Standalone. The GUI for mental ray is Maya itself — the mayatomr plug in.

  3. rachyd says:

    From that point of view, it’s ok., runing from the servet like you sad.But the coders can make “GUI mean all things for us”.
    Leave one for the server and build one for the artist with Gui! independant of Maya or other 3D package.
    And all that dozens nodes converted to a simple buttons like we have in maya!

  4. Nice post. I used to be checking continuously this weblog and I’m impressed!
    Extremely helpful information specially the closing section 🙂 I maintain such information much.
    I was seeking this particular info for a very lengthy time.
    Thanks annd good luck.

  5. Glenn says:

    This seemed promising for porting materials from other applications … but you can’t even connect texture nodes to it, so this is mostly a toy right now. Doesn’t seem to have changed in the new Maya 2016.5 release, either.

    1. Steffen says:

      You can apply existing MDL material designs, but not really edit their internals at the moment. On the other hand, you could create your favorite variation of an MDL material in another Iray capable application and use that with mental ray.

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