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In this tutorial we are going to explore “how to” render the low poly mesh that was exported out of Mudbox with mental ray for Maya , and match the same number of polys of the high rez. model in Mudbox.
This approach is considered the most forward and easy to understand.Open your Mudbox file and note the number of polys that your mesh has.

This number is located either in one of these 3 places.
1.  The “HUD” highest level Display info
2.  The Status line at the bottom right corner of the UI.
3.  The Object info tab

Step down to the lowest Level

Export the low poly mesh as an OBJ
In Maya, open the option box for the OBJ import and disable “create multiple objects”, thus importing the mesh as “one” unit.

A good practice would be double checking the UV integrity to insure NO broken UV edges or flipped UV shells.
This can be done by opening the UV texture editor and toggle “Border edges ON” and “Shaded UV “

Image Description: Good UV screen

1. Example of broken UV edges
2. Example of flipped UV shell

Image Description:

Bad UV screen Select the mesh, and click on ‘ctrl’ + a to open the attribute editor.
Under the shape node for the mesh, disable the “feature displacement”.

This gives us a “manual control” over the displacement assignment for mental ray.
To add the node that will allow us to subdivide the mesh in render time will do the following.
While the mesh still selected:
Window > Rendering editor > mental ray > Approximation editor

Image Description: Sub-D Choose Subdivision (Polygon and Subd. Surfaces) and click “Create”. A new node will be created “under the mesh shape node.

At this point, you will be greeted with different types of subdivision methods. For the sake of simplest we will choose “parametric “ Now we need match the number of Subdivisions to match the Mudbox highest level.
Note: The low poly mesh in Mudbox is called Level 1. To get to level 4 (as in my Mudbox highest level example), we divided the mesh 3 times, therefore in the N Subdivisions, enter the value 3.

Change to mental ray as your render engine In the script editor type:
select mentalrayGlobals;
Open the Attribute Editor of this node and change the verbosity level of Translation to “progress Message”

Render again and notice the Output window message “GAPM 0.3 info : triangle count (including retessellation) : 981504” This is the number of Tris that get tessellated in render time divide that by 2 = the number of Quads = 490752 = the same number in Mudbox Assign the displacement map from mudbox (preferably Open EX 32 bit) Change the mental ray render settings quality to “Production”

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