Vray To Mental ray

Cortesy OF:
http://jamiecardoso-mentalray.blogspot.com/2010/01/mental-rayconverting-vray-max-scene-to.html

In production/Architecture/3D visualisation companies, it is very common for users to inherit/acquire 3D scenes with incompatible rendering engines and shaders/bitmaps.
The majority of these 3D scenes come in VRay (i.e. Archmodels; Turbosquid; etc). Due to the amount of geometry/3D scenes that one may require converting, it is often commendable to use script/s to speed up this otherwise tedious and time consuming process. 
The following steps will help you fast track the above process:


1-One needs to have a version of vray (i.e. even a Demo version would be ok) compatible with your version of Max, already installed. It is highly advisable to work in a separate Max scene to the main one, to prevent merging any possible bugs; missing bitmaps; etc.
Once the conversion/s is/are completed and "stress tested” for errors, then it is safe to merge it/them into one's main scene.


2 –Open your Vray Max scene and run the script as described in The Book.





3-Now that the scene had been converted to mental ray; you need to load the mental ray renderer. Some of the original Vray material slots may become empty during the conversion. Open the "material/map browser" dialog to view all materials in the scene. Select a slot in the material editor. Back on the "material/map browser" dialog, double click on any of the newly converted mr materials to load it in the material editor. Repeat the action with all relevant materials from the "material/map browser" dialog. 






4-When converting the scene from Vray to mental ray, the script tries to maintain the integrity of each material (i.e. glossy levels, bitmaps, values, etc) however, certain materials may still require some attention:

Prior to moving bitmaps and/or changing mental ray presets, one should make a copy of the relevant slot/s for reference purposes(i.e. drag and drop it onto another slot).
This is mainly in case one requires copying and pasting settings/bitmaps from the reference copy onto the new preset. 




Vray reads opacity as white and mental ray reads it as black. As result one may require inverting colours in order for mental ray to read them accurately.
To do this, simply check/enable the "invert" function, on the bitmap "output" parameters". 
The opacity bitmaps require moving to the "cutout" toggle, under the "special purpose map" parameters. 



Since there are mental ray preset shaders for most real world materials, you may wish to apply these physically accurate template shaders to some of these newly converted materials. 
Some of the most popular templates used are: Metal materials (i.e. chrome, brushed metal etc); Glass (i.e. glass thin geometry; glass solid geometry for thick glass and glass physical for goblets, champagne flutes etc); glossy plastic; water; masonry and promaterial shaders. 

Some of these new templates may have the diffuse colour values very low; simply increase it to 1.0. 
Also the colour "diffuse" toggle may be disabled by default; simply scroll down to the general maps parameters and check the "diffuse" color toggle to enable it.






Also, increase the "fast glossy interpolation" value preset as explained in our book. 
To clear all unused Vray materials in the scene, simply click the "utilities" menu from the material editor.
On the dropdown list, choose the condense material editor slots function. 
To be on the safe side,some users also choose the "reset material editor slots" utility thereafter. 
Finally, in the material editor, one can reload the shaders being used in the scene as described earlier; test render the scene for any possible errors and merge it/them into your main scene.