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  1. #1
    Join Date
    Aug 2002

    Exclamation Introduction and FAQ!

    Thread last updated on the 1st of March '05 - Updated the FAQ question on Mental Ray DVDs

    Welcome to the one, the only....... Mental Ray sticky thread!

    This thread was created to help get everyone up to speed on one of the industries leading renderers, and how we can use it now that it's a part of Maya. We can also use this thread to post images rendered with Mental Ray etc.

    For this thread I will create a FAQ, a glossary of rendering terms often heard when using Mental Ray, a hopefully up-to-date, maintained list of all the latest and greatest shaders, and a list of Mental Ray tutorials. Of course, anyone is free to post tutorials and shaders and whatever else they like!

    To help find things in this thread which will hopefully grow to an enormous size, don't forget you can use your browsers Find or Search function!!

    Why should you care about learning to use Mental Ray? Well, just take a look at this gallery on the Mental Ray website:

    The Matrix trilogy, the Starwars movies, The Hulk, Terminator 3, Panic Room and Fight Club are just a few of the big movie productions that Mental Ray has been used on! Now stop drooling and start rendering! (was that lame? I have a feeling that was lame...)


    2.Tutorial List
    3.Shader Information
    4.Potentially Something


    >What is Mental Ray?

    Mental Ray is a renderer that has been created by
    Mental Images.

    >Is it any good?

    Yes! It is reguarded as the industry standard renderer for doing photorealistic rendering. It can do all the fancy things that a renderer needs. Mental Ray has been used to render scenes from movies such as the Matrix trilogy, Panic Room, Fight Club, The Hulk, the Starwars movies etc.

    >How much does it cost?

    Well, for the average user, nothing! If you own Maya 4.5 or later, Mental Ray is free as part of the software (for Maya 4.5 you have to download it). Mental Ray can also be bought as a stand-alone rendering application, which is what you'd need to do for rendering on lots of computers (ie a render farm). For more information on the stand-alone application, click here!

    >Where can I get it?

    If you own Maya 5 or greater, you already have it. It's built in as one of the standard renderers. For Maya 4.5 it is available as a free downloadable plugin from the Alias website. To get the plugin you have to sign up for a free Alias community membership (also called Bronze Membership now) and then click here to download it!

    Update: Maya 6 PLE now includes Mental Ray!

    >Are there different versions of Mental Ray?

    Yes. As with just about any program, as improvements and new features are added, new versions of the software are released. With each release of Maya since version 4.5, a newer version of Mental Ray has been included. The latest release is Mental Ray 3.4 which is integrated into Maya 6.5.

    >Integrated into Maya? Where?! And/or Mental Ray is gone, help!

    This depends on which version of Maya you have. With each new version of Maya since 4.5, Mental Ray has become integrated more tightly with the rest of Maya. For details on how where to find Mental Ray in your version of Maya, just look in the help files! For Maya 4.5 there is documentation that came with the downloaded plugin.

    However! If you really can't find Mental Ray anywhere in Maya, there is one basic thing you can do. Even though Mental Ray is integrated with Maya after version 4.5, it is really just a plugin still. Plugins in Maya can be loaded or unloaded! By default in Maya 5 and 6, the Mental Ray plugin should load automatically, however if you can't find Mental Ray there's a chance that it's not loaded after all. To check, go to:

    Window > Settings/Preferences > Plug-in Manager

    Here you can see a list of all the plugins you have available. You can tell if they're loaded or not by looking at the 'loaded' checkbox to the right of the plugin's name. The next checkbox across ('autoload') tells Maya to load the plugin automatically each time Maya starts.

    Now, the plugin we're looking for is called 'Mayatomr.mll'. You should be able to find it in the list, and load it by ticking the 'loaded' checkbox if it isn't loaded already! Tick the 'autoload' checkbox too if you plan to use Mental Ray often.

    >Is Mental Ray hard to use?

    That depends on your previous rendering experience. Most high-end renderers can be quite technical, but if you follow some tutorials and read parts of the help files, you should start to understand it fairly quickly. Don't worry, you don't need to be a programmer or physics genius to render your average scene. As always, each new release of Maya has Mental Ray integrated even more, so it becomes easier to use.

    >I've heard that 3DS Max and XSI have Mental Ray too, is Maya's the same, better or worse?

    That's a tricky one. At the time I'm originally writing this, you could say that Maya has the same Mental Ray as XSI, and that they both have a better one than 3DS Max. That's because XSI and Maya both have Mental Ray 3.3 integrated into them, while 3DS Max only has Mental Ray 3.2. Mental Ray is Mental Ray no matter what it looks like integrated into a 3D package. However, the integration is what you can describe as better or worse.

    I don't think many people would argue with me when I say that XSI has the 'best' integration of Mental Ray. Why? Because XSI has used Mental Ray as it's sole renderer since version 1. Mental Ray is completely integrated into every aspect of XSI, it's fast and easy to use (if you like XSI).

    Maya's current integration (in Maya 6) is very good, but has room to improve. Most of Maya's features are supported for rendering in Mental Ray, and most of Mental Ray's main features are accessible through Maya. For a list of limitations, please, see your doctor. Err, I mean the help files! Like I keep on saying, with each release of Maya, we come closer to the perfect integration.

    Update: 3ds Max 7 and XSI 4.2 have Mental Ray 3.3. Maya 6.5 is in the lead again with version 3.4, hehe.

    >Are there official Mental Ray books?

    Yes. Mental Images has written two books on Mental Ray. They are called 'Rendering with Mental Ray' and 'Programming Mental Ray'. The latter book requires programming knowledge (ie C++), but the first book is just a good handbook. Something you really need to know is that there are first and second editions of each of those books! Make sure you get the second editions if you can because you don't really want to buy an outdated book. Unfortunately the second editions are named the same as the first ones, and look nearly identical too (I think!). You can buy the books by clicking here! (Yes it's the second edition).

    Update: A 3rd edition of 'Rendering with Mental Ray' will be out in October this year. Not only is it updated for Mental Ray 3.3, it also contains the entire second edition of 'Programming Mental Ray' on the CD that comes with it! You can already pre-order it by clicking here.

    >Are there official Mental Ray training DVDs?

    Not by Mental Images themselves, but Alias has created one:

    Maya Techniques | mental ray Custom Shaders

    It's an advanced DVD though, not for beginners.

    Digital Tutors has one DVD:

    Fundamentals of Mental


    And Digital Tutors also has a downloadable video pack (still costs money):

    Mental Ray e-download

    The Gnomon Workshop has 3 DVDs:

    Mental Ray: Fundamentals
    Mental Ray: Lighting and Shaders
    Mental Ray: Global Illumination

    >I don't need to render anything of super photorealistic quality, can I just use Mental Ray for 'normal stuff'?

    Yes you can. Mental Ray is an all-round good renderer, not just for photoreal film animation/effects. It's fast and reasonably simple to use for every-day renders of your models and scenes. However, if you're just starting out in Maya and like to experiment with all of Maya's great crazy features, you might be better off sticking to the Maya Software renderer. Just so that you don't have to worry about any compatibility issues.

    >I really like Mental Ray! Can I set it to be my default renderer in Maya?

    Yep! Go to:

    Window > Settings/Preferences > Preferences

    From the left hand side list of catagories, click on Rendering. Then in the main section on the right, select Mental Ray as your preferred renderer. Note, if you don't have the Mental Ray plugin set to 'autoload', next time you start Maya there could be problems because it won't be able to find it's preferred renderer!

    >What does Mental Ray have that the Maya Software renderer doesn't have?

    Well, a lot of things really. Some of the more significant features are Global Illumination through both radiosity and photon mapping, Caustics, motion blurred shadows and reflections, volume caustics, Final Gather, photometric lighting.......and lots more.

    If you went "wuh??" to any of those terms, don't worry. There is a glossary type of thing further on in this post/thread.

    >I keep on hearing about this or that Mental Ray shader, that does <insert potentially confusing term here>, what are these shaders?

    Mental Ray shaders are a big part of Mental Ray's power. Unlike the normal use of the word 'shader' that you probably know about, describing a material that looks like concrete, or grass or whatever, Mental Ray shaders can do many more things than these traditional shaders.

    A shader in Mental Ray could still make something look like grass, but it could also create a light! Or create geometry! It could change the lens on your Maya camera, or apply an effect like fog or depth blur to your scene. Mental Ray shaders basically make up most of your scene. Of course, you don't really need to know that because Maya takes care of most of these shaders in the translation of your Maya scene at render-time.

    However, if there's an effect or look that you need to achieve, and Maya doesn't already have a feature for it, say for example Sub-Surface Scattering, Ambient Occlusion or a a Telephoto Lens (sorry for the technical terms, more on them later), a Mental Ray shader can often come to the rescue.

    To sum all that up, Mental Ray shaders are cool and can do lots of useful things!

    >Ok, so where do I get some of these 'cool' shaders from?

    The internet. Or if you're really smart and know how to program, you could try writing them yourself. Now that Mental Ray is becoming a lot more mainstream, more and more shaders are being created by artists, and posted for free on the internet. Which is really great! They're a bit scattered around on message boards and personal websites though, so if I (or you) find any cool ones we should post them in this thread for easy access.

    >Wait a minute, I'm having a revelation! If 3DS Max, XSI and Maya all have Mental Ray integrated now, does that mean a Mental Ray shader created for Max or XSI will work in Maya?

    Basically yes! Not right away though. There are a few files that make up each shader (more on that later), and only the Mental Ray specific parts will be compatible straight away. The other files for the shader tell the specific 3D program how to use them, and what the interface for the shader should look like. Someone needs to create Maya specific versions of those files in order for them to work properly (or even load) into Maya. Luckily, if a great shader is created for Max or XSI, chances are that someone will soon port it over to Maya.

    Isn't that kinda nice? Shaders re-uniting the global community and breaking down the barriers between 3D apps? Ehem, just forget I said that part.

    >Does Maya come with any Mental Ray shaders?

    Yes. If you look in the Hypershade, or that popup window that appears when you click on a mapping slot next to an attribute of a shader, you should see a section called 'Mental Ray' (how surprising!) that has quite a lot of shaders in it.

    >Err, I don't see them!

    Yes I know, hehe. If you have Maya 4.5 or even 5, chances are you won't see these Mental Ray shaders. They need to be specifically loaded. I have a tutorial on loading these shaders here! Maya 6 should definitely have them loaded by default.

    >Cool, what do they do?

    Umm, stuff. There are too many to explain each one here, and depending on your version of Maya, some of them might not work properly anyway. The best way to learn about them is to just follow tutorials on Mental Ray that you think look cool. If a tutorial requires you to use one of the shaders, it should hopefully tell you all about it. (I know I do in my tutorials)

    >How do I use them?

    That's a similar question to the one above. Just follow tutorials and they'll tell you how to use each the different shaders.

    >Are new Mental Ray shaders easy to create?

    Well....generally no. Not for the average user. In order to create a brand new shader you need to know how to program in C, compile the code etc.

    >I want a shader that creates pink firey water! Can you make it for me?

    Sorry love, the pink firey water will have to wait. I'm afraid I don't know much programming at all, therefore I can't write you a new shader! Cheer up, someone who does will surely need pink firey water some day too.

    >What are the files that make up a Mental Ray shader?

    When you download a Mental Ray shader for Maya, there are typically 4 or 5 types of files included:

    *.dll - The dll files are the actual shader code. They are what give all the instructions on what the shader is supposed to do when it's rendered. These files go in your:

    "C:\Program Files\Alias\Maya6.5\mentalray\lib" folder.

    *.mi - The files that end in .mi are written in the Mental Images MI format. They are just text files. They give Mental Ray some general information about the shader, and tell Maya what attributes you would like to have present inside Maya for tuning the shader. They also tell Maya what section of the Hypershade the shader should be found in (ie Textures or Materials etc). These files go in your:

    "C:\Program Files\Alias\Maya6.5\mentalray\include" folder.

    *.mel - The .mel files are usually named something like AEshadernameTemplate.mel. AE stands for Attribute Editor. What these MEL files do is create the interface for the shader inside Maya's Attribute Editor. Without these files you would still be able to edit the shader in the Attribute Editor, but Maya just generates a very basic interface which is believes is appropriate. These files go in your:

    "C:\Documents and Settings\username\My Documents\maya\6.5\scripts" folder.

    *.xpm - These are Maya icon files. They simply provide an icon for the shader in the Hypershade's Create Bar. These files go in your:

    "C:\Documents and Settings\username\My Documents\maya\6.5\prefs\icons" folder.

    *.fti - Not that many people include these files, but more people are starting to. They are also Maya icon files, but they create the Hypershade node icon that is visible when you see your shader in the Hypershade's flow area. Without these icons you just get a default 'mental ray shader' icon. These files go in your:

    "C:\Program Files\Alias\Maya6.5\icons" folder.

    >What is Mental Ray for Maya Satellite?

    Mental Ray for Maya Satellite has been introduced with Maya 6.5. It is a free (for Maya 6.5 users) separate application that allows other computers to assist in all Mental Ray rendering tasks, such as rendering with Mental Ray inside Maya, batch rendering with MR, IPR rendering with MR, texture baking with MR etc etc.

    >Like a render farm? Isn't that what Mental Ray Standalone is for?

    Well, yes and no. Mental Ray Satellite is like a mini renderfarm that only listens to Maya. Mental Ray Standalone can accept custom written MI files, and scenes from most apps that have a connection to Mental Ray. Mental Ray Satellite doesn't really have any manual operation, it just assists Maya with whatever it can.

    Also, Mental Ray Standalone can be used in renderfarms of enormous size, whereas Mental Ray Satellite is limited in the number of computers it can be used on.

    >What's the limit on Mental Ray Satellite then?

    The limit is based on the number of CPUs, not the number of computers. For users of Maya Complete, Mental Ray Satellite will utilise up to 2 external (being not on the machine with Maya) CPUs for assisting rendering. So that means 1 dual processor computer, or 2 single processor computers can assist with rendering.

    For users of Maya Unlimited, Mental Ray Satellite accepts help from up to 8 external CPUs.8 extra CPUs helping with all your rendering tasks is a pretty nice boost!!

    >Is Mental Ray Satellite good? What do I need to use it?

    Yes, I think Mental Ray Satellite is very good. Rendering is the slowest part of CG and all the (free!) speed boosts we can get are great. In order to use Mental Ray Satellite, you need Maya 6.5 or greater, Mental Ray Satellite itself and at least 2 computers (the one with Maya and the one that will assist) that are networked together. Having a fast network (100mbit+) is fairly important because a lot of files and data are transfered around (especially at the start of a render).

    I myself have an 802.11g wireless network at home that I'm using MR Satellite on, which is only a maximum of 54mbit. While it still works well, there is quite a wait (3 minutes+ at times) at the start of renders while the scene file and texture files etc are transferred around. After that initial wait though it seems fine.

    >Can Satellite help the Maya Software/Hardware and Vector renderers?

    No! I've seen quite a few people ask this. It's called 'Mental Ray for Maya Satellite' because Mental Images and Alias have put this together for Mental Ray rendering only.

    >Has Mental Ray ever been used to render a full length CG film?

    Yes, there are possibly a few that have been rendered with Mental Ray, but the recent one is Shark Tale by Dreamworks.

    >Can Mental Ray do 'toon/cel/anime' style rendering?

    Yes, in Mental Ray this type of effect is called Contour rendering.

    End of FAQ for now!
    Last edited by Jozvex; 03-01-2005 at 01:58 AM.
    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  2. #2
    Join Date
    Aug 2002

    I should tell you that most/all of these definitions are coming straight off the top of my head, but most of them should be right I hope. I'll definitely look stuff up if I'm not 90% sure! And feel free to yell at me if you think I've said something crazy. The Glossary is roughly in alphabetical order.

    (I've thrown in some you'll probably never need to know, just for fun, hehe.)

    * Aliasing

    Often referred to as 'jaggies', aliasing is what occurs in renders when not enough samples are taken from the scene. The most common example is the stair-stepping effect seen along the edges of objects and highly contrasted areas of your image.

    * Anti-aliasing

    Techniques to combat aliasing like oversampling/supersampling and filtering.

    * Adaptive Sampling

    A technique used to anti-alias your image really well, while still keeping rendertimes low. Adaptive Sampling adjusts it's level of anti-aliasing over different parts of the image. Using less/more where less/more is needed etc. You need to tune these settings to work well for each scene.

    * AO (Ambient Occlusion)

    Ambient Occlusion is an effect that is often used in movie/TV animation as a replacement to GI or Final Gather. It is used as a replacement because it can be much faster to render and easier to control. It's called Ambient Occlusion because it does two things. It looks at the environment colour (which could be a flat colour, or could also be an image, eg HDRI) and applies some ambient lighting to the object based on that, then it also darkens the object in areas where there are creases, or anywhere else in which two or more surfaces are close together. The example render below shows two scenes in which only Ambient Occlusion was used, there are no lights. In Mental Ray, Ambient Occlusion is available to us via the Dirtmap shader (see the shaders section of this thread). A common technique is to render our your scene normally to get a Beauty pass, then render out a separate Ambient Occlusion pass for adding to your to final composite.

    (click here to see an example render)

    * BRDF (Bidirectional Reflectance Distribution Function)

    More or less the way to describe how light interacts with a surface at any given point.

    * BSSRDF (Bidirectional Sub Surface Reflectance Distribution Function)

    Hehe, more or less the way to describe how light interacts with a semi-translucent surface at any given point. (ie skin, wax, other organic surfaces)

    * BSP (Binary Space Partitioning)

    BSP is a method of accelerating the raytracing calculations performed during rendering. BSP settings in Mental Ray can greatly affect rendering time!

    * Caustics

    The light patterns created by focussed refracted or reflected light.

    (click here to see an example render)

    Download the scene for Maya 5 or Maya 6

    * Cornell Box

    Not really a rendering term, but it's a type of scene sometimes used to illustrate examples of Global Illumination etc. A Cornell Box scene usually looks like a small room with different coloured walls, containing some cubes. Cornell university created a miniature scene like this (in real life) to observe how light bounces around in a scene. These days, people often test their fancy renderers by comparing a digital version of this scene to the real thing. For more info, click here to go to the website of the real Cornell Box.

    * Diffraction

    The effect of light being seperated into it's spectrum of colours when it is refracted through hard edged surfaces, like a prism.

    (click here to see an example render)

    It's not the nicest example but hey.

    * DOF (Depth of Field)

    The effect that creates out of focus blurring, for parts of your scene that are too close or far from the camera.

    (click here to see an example render)

    Download the scene for Maya 5 or Maya 6

    * FG (Final Gather)

    A Mental Ray feature that can be used for creating that classic 'GI' look, often used for showing off models. It can also be used for HDRI, object lights and for smoothing out GI.

    (click here to see an example render)

    Download the scene for Maya 5 or Maya 6

    * GI (Global Illumination)

    The simulation of realistic environmemt lighting. With a normal scene containing one spotlight in Maya, things that fall within the cone of the spotlight are lit, those that don't are black. Using GI, Mental Ray will calculate the way in which light bounces around a scene, creating secondary bounce light and other effects such as colour bleeding. Using Global Illumination can lead to extremely realistic lighting.

    (click here to see an example render)

    Download the scene for Maya 5 or Maya 6

    * HDRI (High Dynamic Range Image)

    An image file that contains much more colour and intensity information than a regular BMP or JPG file. Because these special images contain so much more data, you can actually use them to light your scene! The ultimate use of HDRI is to take photographs of a real-world set, then use HDRI to accurately light your Maya scene exactly the same way the real location was lit! All without lights! Common file extensions of HDR images are .HDR, .MAP and .TIF.

    (click here to see an example render)

    * IBL (Image Based Lighting)

    A technique of lighting your scene with images rather than lights. HDRI being one such IBL technique.

    (click here to see an example render)

    * Micropolygon Displacement

    The ability to create enormous detail through displacement at rendertime, on low polygon geometry. You don't need a really dense mesh to create detailed displacement, because Mental Ray can create any additional geometry at the micropolygon level (smaller than the initial polygon).

    (click here to see an example render)

    Download the scene for Maya 5 or Maya 6

    * Ray

    (I'm going to do my best to explain this, if you see something wrong then let me know!!)

    A ray is basically an imaginary line that is 'cast' from one place in your scene to another in order to sample a property for rendering. There are quite a few different 'types' of rays depending on what needs to be sampled. Here are some of them and what they do:

    Eye Rays: These are cast into your scene from the camera, through the pixels of your image, in order to sample which objects need to be rendered, and how the pixels they were cast through should look (more or less). These rays are used in both Scanline and Raytracing renderers.

    Reflection/Refraction/Secondary Rays: These are cast from each point on a surface (that an Eye Ray has hit) that is reflective/refractive, out into your scene to determine what should appear in that reflection/refraction. These rays are only used by Raytracing renderers, or when the Raytracing feature of a primarily Scanline renderer (such as the Maya Software renderer) is turned on.

    Light Rays: These are cast from each point on a surface (that an Eye Ray has hit) towards the lights in your scene, to find out the properties of the light.

    Shadow Rays: When using Raytraced Shadows, an Eye Ray has been cast from the camera to your object, then a Light Ray goes from that point on the object to a light source, then finally a Shadow Ray is cast from the light, back along the same path as the Light Ray to see whether anything is blocking the light from your object. If something is blocking the Shadow Ray's path, then obviously that point on your object must be in shadow. This ray type is only used by Raytracing renderers or the Raytracing feature of a primarily Scanline renderer.

    * Raytracing

    Raytracing is a rendering process that can calculate things like reflections, refractions, GI and other complex rendering effects. Raytracing is often thought to be slow, though these days a lot of renderers such as Mental Ray and Brazil are built for speed when raytracing.

    * Scanline Rendering

    A fast rendering process that renders your scene one row of pixels (one scanline) at a time. Scanline rendering is often fast, because it doesn't calculate things like reflections, refractions, and other more complicated rendering effects.

    * SSS (Sub-Surface Scattering)

    The effect of light penetrating a surface and illuminating the inner layers. This is very important when creating realistic skin and most other organic materials. For example, if you (in real life, hehe) press a strong torch up against your hand, you should be able to see the light illuminating your hand from the other side.

    * Texel

    A pixel that is part of a texture map.

    * Uniform Sampling

    A method of anti-aliasing that applies the same amount of anti-aliasing to the whole image. It can give great results but can be pretty slow.

    * Voxel

    A volume of pixels. For example Maya Fluid Effects uses voxels, it isn't real geometry (unless you tell it to be), just a volume of pixels!


    More to be added later!

    Last edited by Jozvex; 08-27-2004 at 05:11 AM.
    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  3. #3
    Join Date
    Aug 2002

  4. #4
    Join Date
    Aug 2002
    Shaders Information!

    Mental Ray shaders can be extremely powerful, this post will contain information on the Mental Ray shaders that come installed with Maya, and how to install and use the many great shaders that people have created and posted online.

    Shaders that come with Maya 6

    Materials – Connect to Material Shader slot & most colour attributes.

    Material shaders in Mental Ray are what provide an object with it's main surface properties, just like regular Maya materials. Why use a Mental Ray one instead then? Well because people create many advanced material shaders for Mental Ray all the time, that offer things like Sub-Surface Scattering, Ambient Occlusion and many other powerful effects. These standard ones that come with Maya 6 are for the most part pretty unexciting, but some are quite cool.


    This is a simple shader with few attributes. DGS stands for Diffuse, Glossy, Specular because those are the three main properties this shader offers, along with Transparency. The Glossy and Specular attributes provide reflectivity. Glossy reflections are blurry. The blurriness is controlled via the Shiny attribute, the lower the blurrier. When Shiny is set to 0, the Shiny_u and Shiny_v attributes can be used to blur the reflections non-uniformly (eg blurred more horizontally than vertically). Maya 6 now provides blurry reflections and refractions on standard Maya shaders, so it is better to use those instead because they can be tuned for quality vs speed whereas the Dgs_material cannot. Also, the ability to create non-uniform blurring with the Shiny_u and Shiny_v attributes only seems to work reliably on NURBS surfaces.


    Mental Ray equivalent of the blinn shader. Use Maya's intstead.


    This shader is basically a blinn shader for use on Mental Ray hair geometry. Not much use for it, if any.


    Mental Ray equivalent of the phong shader. Use Maya's intstead.


    This is more or less like a DGS shader with Ambience attributes. Also, the ability to create non-uniform blurring with the Shiny_u and Shiny_v attributes only seems to work reliably on NURBS surfaces.


    Transmat material shaders make things invisible. This can be usefull if you want something to have a volume shader (for example) applied to it, but have no surface.


    The Dielectric material is very good for creating refractive materials such as glass and water. It's a little bit complex because it relies on you having the normals of your object facing the right way depending on the effect you want. 'Col' is a colour representing how much light can pass through the object. 'IOR' is the Index of Refraction. The IOR is most important for changing the type of material you're trying to achieve. For example glass has an IOR of roughly 1.55, while water has an IOR of roughly 1.33. Now, what this shader does is act like a conversion between two substances. The 'Col' and 'IOR' attributes control what the substance will be on the opposite side to the object's normals...for example on the inside of a default poly sphere. The 'Col_out' and 'IOR_out' control what the substance will be on the side the normals are facing...for example on the outside of a default poly sphere. On the default settings (at least in Maya 6) this shader is ready to use as glass because the 'IOR' is 1.5 (meaning glass on the inside) and the 'IOR_out' is 1 (meaning air on the outside). If you were creating a glass ball that is inside water, you would change the 'IOR_out' to 1.33. This shader uses the laws of Fresnel (reflections/refractions are strongest on surfaces facing away from the camera) and Beers law (light is absorbed as it goes further through). Beers law affects the shader in that if you've set the 'Col' attribute to 0.85, then 15% of the light entering the surface is absorbed every unit (in world space) as it travels through the object. The 'Ignore_normals' option ignores the way the normals of your object are facing. This can be usefull if your model is a little bit wacko and the normals aren't right. I think using this option may be slightly slower to render as it has to do more calculations instead of just reading the normal direction. 'Phong_coef' adds a fake specular highlight.


    This is similar to a blinn shader, only it has an IOR setting that allows you to control the way the specular highlight looks at different angles to the camera (basically Fresnel). The IOR colour has to have a value greater than 1 to work. I can't really see a use for it as a shader by itself.


    Mental Ray equivalent of the lambert shader. Use Maya's intstead.


    Same as the other ward shader only this one lets you map the U and V coordinates in order for Mental Ray to know which way the Shiny_u and Shiny_v attributes should blur the reflection. This seems to allow the blurring to work properly on both NURBS and polygon objects. I think that you need to use the Mib_texture_vector node to do the mapping. In Maya 6, just use standard shaders as they can do the blurring anyway without the hassle.


    The Path material seems like just a simple DGS material...only it's not! It not only is a DGS material but it calculates Global Illumination too! No photons or Final Gather are needed, the shader does it all by itself. The GI it calculates is very accurate too, more-so than normal photon mapped GI. Why isn't everyone using it then? Because it's VERY slow if you want good results. In order to not have any graininess, you need to use very high sampling settings in the Render Globals like Min 4 Max 4. It uses what's known as brute force Monte Carlo sampling to calculate the GI. You can control the number of lighting bounces this shader calculates by setting the raytracing Reflection/Refraction and Max Trace Depth attributes in the Render Globals. For example, setting the Reflections attribute to 5 in the Render Globals and the Max Trace Depth to at least 5, the Path shader will calculate 5 bounces of light. One strange thing is that the shader doesn't seem to work with transparency/refraction.

    Shadow Shaders – Connect to Shadow Shader slot.

    You apply a shadow shader to the object whose shadow you want to modify.


    This shader allows you to change the colour and transparency of shadows. Transparency values of less than 0.5 seem to create solid opaque shadows. As far as I know you must set the 'Mode' to 1 for it to work.

    That's all so far sorry!
    Last edited by Jozvex; 09-09-2004 at 05:01 AM.
    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  5. #5
    Join Date
    Aug 2002
    Potentially Something!

    Would you look at that? It's me again! To be honest I might not even need a fifth post, but I'm making a place-holder just in case, maybe this could be a user gallery of Mental Ray renders!
    Last edited by Jozvex; 08-08-2004 at 06:04 AM.
    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  6. #6
    Join Date
    Aug 2002
    1,685 the story goes that originally all my above posts were all crammed into one massive post, which was less than desirable because if I linked someone to the Glossary, they had to scroll way down past the FAQ etc etc. So then because you can't insert new posts (other people posted after my mega post), I basically decided to re-structure the whole thread by copying it and merging stuff over, however my control over my mod-ly powers isn't as good as I thought, and I lost everyone else's posts. Sorry about that, but I managed to rescue the links you posted, so they've been put into the tutorial list post.

    Anyway, now we can start again with a much better organised thread which should benefit everyone.

    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  7. #7
    Join Date
    Aug 2002
    A Contents! Why didn't I think of that hehe, nice suggestion Phrenzy I'll add that now.

    Don't be scared to post by the way guys, I won't be deleteing peoples' posts again hehe.
    Read the new (constantly expanding) Mental Ray sticky thread for info on Mental Ray in Maya! It includes a FAQ, Glossary, a list of tutorials and info on the latest MR shaders!

    Click here to see my showcase page.
    And here to see my Maya tutorials (7 so far).

  8. #8
    Join Date
    Jun 2002
    London, UK
    no problem, yeah people post, this is a big subject , but i will be doing my best to keep things clean so ill delete my old post, no point in being there.

    best MR faq anywhere.

    edit:// plus you have more post to add to

    insert witty comment here

  9. #9
    Join Date
    Sep 2003
    Hey Jozvex,

    Alias is revamping their community/learning areas (due to the new Silver/Platinum/etc pay-for-support packages), and the mental ray links that I submitted are dead.

    Here is the source page (scroll down):

    I wrote alias and hopefully they will bring them back online.

    Edit: just checked... Alias fixed them and they are back online.
    Last edited by scottschetrompf; 08-24-2004 at 05:45 PM.

  10. #10
    Join Date
    Jul 2004
    Melbourne, Australia
    I'm not sure if anyone else has had this problem but when I start Maya 6.0.1, the text thingy on the bottom right hand side of Maya reads:

    // Warning: The renderer, mentalRay, used by this scene, is not currently available. The Maya Software renderer will be used instead. //

    Does anyone know how to fix this or is having the same problem?

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