Speed up Revit FBX Renderings in Max Design

A simple change in the DesignVIZ options can vastly improve mental ray Pre-Processing when rendering scenes imported from Revit FBX files.
In Notepad, open the file "CurrentDefaults.ini in your local User's files (typically at C:\Users\YourUserName\AppData\Local\Autodesk\3dsMaxDesign\2010 - 32bit\enu\defaults\DesignVIZ.mentalray\CurrentDefaults.ini").
Search for the parameter 'DontRepeatRefMsg' and change it's value from 0 to 1.
Four lines down is the parameter 'InvalidateTMOptimization' and change it's parameter from 0 to 1. You should now have:
DontRepeatRefMsg=1
; comment comment comment...
; comment comment comment...
; comment comment comment...
InvalidateTMOptimization=1
Pre-Processing at the start of mental ray rendering should now happen in a few seconds instead of minutes.
You have to restart Max to accept the change. You should also edit the DesignVIZ.mentalray preset at your program installation folder, usually "C:\Program Files\Autodesk\3ds Max Design 2010\Defaults\DesignVIZ.mentalray\FactoryDefaults\CurrentDefaults.ini"
Be sure to do the editing for both x32 and x64 if you have both installed. Editing the INI file in the Max installation folder prevents a change if you choose an option from the "Customize>Custom UI and Defaults Switcher".

Source website:
http://newsletters.hagerman.com/newsletters/ebul81-ME.htm