Mental Ray Basics


Thanks Psychodad.
I asked the same question a few months ago and here’s the response I got.
“How Did you learn Mental Ray?”
Looks like aside from a few books everyone learned through trial and error and lots and lots of time.



how can i connect the mib_reflect to the sphere as is showed on page 1


Hi Zim_invader

In this thread you mentioned combining the bumpCombiner to the mix8layer… I still don’t get it. Is there any chance you could make a demo file so I/we can download it and look at the connections you’ve made??

Here’s what I’m talking about:

Please help. :slight_smile:


Take your Phong or transparency and connect it to the “Input” of the transparency. And connect your reflectivity map into the “reflect.” And then to connect the reflect node to the SG (shading group) you drag it and open the Connection editor and connect:
OutValue ----> Mi Material Shader

On another note I’ve had some issues with double sided polys and transparency in Mental Ray and i found the MI_Continue node works similarly to the Transparency so if anyone has problems try that one too. It’s found in the same “Sample Compositing” tab.

No need to put up a sample file it’s a simple connection. I was sucessful with MMB dragging the Mix8Layer to the BC and choosing “M-input” (The two M_inputs represent the two shaders allowed in the bump combiner and the other options are the many bump layers).
The connections made are:
I couldn’t find the m_inputA in the connection editor, not sure what that means.

Hope this answers your questions.


connect the out v result of the bump combiner to the base color of mix8


I bet you mean the outC result, because outV returns the bump vector, unlike outC which returns the color…?


i think Nuisance wants to connect the bump combiner for bump purpose only, check a few threads upwards, he wants to connect to mix8, so i assume that he needs only for bump…correct me if i’m wrong


Uhm… I’m a bit confused now, but that’s nothing special… However, I guess Zim already gave the right hint: mixLayer1.outValue—>BumpCombiner1.m_input


yes Zim told about connecting mix8 to bump combiner and i told about connecting bump com to mix8. anyway the solution is there both ways now…bye


Hi guys

Thanks for all your effort in helping me out. However the problem was my stacking-order in the hypershade and not my connections. I kept assigning the mix8lyer to my geometry. However it is the bumpCombiner that is top of the order list that should be assigned to geometry.

Here, this will explain it:



Hehe that’s a very common mistake. I see it at least once a week at work. When something like that doesnt’ work I always select the geometry and show input/output connections to make sure it’s connected correctly.


hey, thanks a lot for the great thread. i am learning MR, and maybe this is a silly question, but i need to ask it anyway. :sad:
say, i am trying to make a bottle filled with wine. i created nurbs curves both for the bottle as well as the wine inside it and revolved them. then, applied dielectric to both the nurbs surfaces. but, i am still confused about how to set col_out and ior_out for both of them. the bottle is made with a curve that gives it its proper thickness. wine on the inside of the bottle is a cylindrical surface.
so, do i need to set the ior_out for the wine, to match its ior value? or, i should i be leaving it at 1? and what about the col_out of the wine? should i change it to match its own col? or should that be the same as the col of the bottle? also, what should be the values for the glass bottle? the bottle is only half full…
i tried a few things here and there, but can’t seem to get the output i want.

or, should i be doing this in some completely different way?? :argh:


it depends on way the normals of your surface are pointing… *_out refers to the material on the side that normals are visible and the reverse for _in.
To display the normals in the viewport use the Display>Nurbs Display>Normals :slight_smile:

say this is your glass (with the arrows as normals), then:
black.out = air and = glass
gray.out = glass and = water
red.out = air and = water



:eek: from looking at your drawing it seems to me that i might have been doing this all wrong. so, i should be making 3 separate surfaces, right? the surface of my glass should end where the edge of the water starts. then, i make another surface that will make the top of the water. and then, i should make another surface that would form the common surface for glass as well as water, right?
so, according to your diagram, for the black surface, i should keep the col and ior to match that of glass and col_out and ior_out should be left at default. then for the grey surface, col = 1, ior=1.333. col_out and ior_out = that of the glass. for the red surface, col = white, ior = 1.333 and col and ior_out = default.
all right, got to give it a try

thanks a lot for your time, yashu… :thumbsup: :thumbsup:


How to render good looking wireframe?


Not sure you need to use Mental Ray for wireframes. But here’s a threadon contour rendering. Or use the Maya 7 toon shader. Or my personnal favorite apply your UV output to the transparency and then turn the color and ambient up to white.


Hey everyone. I’ve been searching all around this thread and many others on mental ray for this and that and I’ve got a rather troublesome problem with The ctrl_bumpCombiner. It works…but only sometimes. I followed a detailed setup that was posted that showed how to set it all up correctly. Well It works but for some reason more times then not when i hit render mental ray wont render tells me it aborted? but if i keep hitting the render buttom ramdomly it will render the scene and the bumpcombiner works adding bump…but then say i hit render again it gives me the same info and if i keep hitting it, it will randomly render the scene. sometimes it seems to work for several renders sometimes never. I know it has to do with the bumpcombiner cause if i diconnect it and apply the material that runs threw it to the surface it renders fine.

I’m using maya 7.0 on a windows XP SP2 machine. so im wondering if theres something to fix this or that i’m doing wrong. I wouldnt’ have asked but i’ve been plungering threw posts for the past threw days and can’t find anything. It also does the same thing with the JS_glare which i wish i could get to work.


Did anyone try using a projection map with the bumpCombiner node

my intital tests didn’t work

the only way I made a projection work with mr custom shader is using the [size=2]mib_texture_vector [/size]
[size=2]and change the projection to cylinderical[/size]
[size=2]but that dosnt give much control over the projection


yencaray: Double check you’ve got the shader installed correctly. Including the mel scripts in your MyDocs.
Also turn the Mental Ray Errors to see what part is having the error. In the render globals/mental ray/translation/ Export Verbosity; change it to progress messages. And check in the Output window (Mental Ray errors dont display in the script editor) for any errors that have a “Error” near the begining of the line.

ashaiad: The projection uses a 3d placement as well as a 2D. I got it to work if i changed the bump2d that connects the projection to the bumpCombiner to a bump3d.


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