Mental Ray Q&A

Hi mental ray users and lovers,

Even though the Mental Ray Forum has disappeared recently from the web, we are here to help you with issues you might have with the Mental Ray plugins or the Standalone. Just ask your questions in the comments and we will try to come up with an answer in a new blog post.

For example, I wonder if and how you are using the GPU capabilities in Mental Ray, like the “GI Next” Global Illumination acceleration, or the fast GPU mode of Ambient Occlusion?

We are also interested in art work and renderings done with Mental Ray that we would love to highlight on this blog.

Happy to hear from you,

Steffen

New Unlimited Mental Ray Satellite / Standalone

Hi all,

we have very pleasant news for those of you who are frequently rendering on remote machines using Mental Ray Satellite that are connected and controlled from a Maya or 3ds Max plugin:

The Mental Ray Standalone does not require a license anymore.
It is completely free to use on any number of machines.

This is a great extension for users of the Mental Ray plugins who depend on network-distributed rendering for more rendering throughput. It is also lifting any restrictions for usage in a render farm when running from the command-line or managed by a render job manager like Backburner.

What is Mental Ray Satellite rendering?

Unlike starting separate render jobs in a render farm, the Satellite rendering mode allows to connect remote machines in the internal network to your main Mental Ray rendering engine, so that they take over the heavy part of rendering the image or animation without stressing your main machine, which is already busy running your DCC tool. You can continue working with Maya or 3ds Max in the usual way, since Mental Ray is handling the data distribution and network communication under-the-hood. Naturally, the network speed and machine configurations have great impact on the overall experience and a fluent workflow.

In Maya, the satellite mode can be enabled selectively for preview rendering in Render View, and also for batch rendering in the background. However, progressive rendering is not supported in this distributed mode. That makes it less useful in the interactive viewport rendering with Mental Ray, although it’s generally possible to enable it there too. You have the option to let Satellites do ALL the rendering remotely, freeing your main machine from any rendering load (perfect for a background batch render), or set them to contribute to the main rendering as needed (like for a quick preview render).

Otherwise, there are no limitations on the number of machines or CPU cores that can be utilized, different to the original Satellite mode in Autodesk products. However, technically, the overall benefit for rendering may decrease at some point when too many remote machines need to be synchronized over a potentially occupied network.

This latest Mental Ray Standalone can also be used from the command-line, of course, now without any restrictions and no licensing setup.

Please download the new installers below for your platform. We provide versions that are compatible with Maya 2018 and 3ds Max 2018 Mental Ray. We have no plans to upgrade to later versions of Maya or 3ds Max.

Happy rendering! ūüėÄ


Downloads

Mental Ray Free Standalone / Satellite

Mental Ray Free Downloads – Links

Hi all,

after decades of supporting the rendering community worldwide, the NVIDIA ARC Forum will go out of service, unfortunately, including all of its mental ray sections. That does not mean its vast valuable content is lost, but we will stop hosting it on the original website location.

For those of you who are searching for the download links of the free Mental Ray software, which we did publish in the forum as well, here you are. We include a copy of the text of the original announcement followed by all the links to the pieces of software.

Happy rendering!


The version 1.2 update of the NVIDIA Mental Ray for Maya and NVIDIA Mental Ray for 3ds Max plugins, and the corresponding Mental Ray Standalone distributions are based on the latest major mental ray version 3.14.5.

This software update introduces support for NVIDIA’s Volta GPU generation, and is based on CUDA 9. It will continue to work with the older GPU generations Pascal, Maxwell, and Kepler. The update also fixes a lot of known issues, and improves rendering performance especially for GI Next. Note, the plugin works in Maya 2018.5 dot release too.

Please note, the plugins are free to use for interactive rendering and rendering of still frames from within Maya or 3ds Max. The rendering of animations with Maya Batch, Backburner or Mental Ray Standalone will ask for a license though.

NVIDIA Mental Ray for Maya Plugin

Windows
Linux
macOS

NVIDIA Mental Ray for Maya Standalone

Windows
Linux
macOS

NVIDIA Mental Ray for 3ds Max

Mental Ray Licensing Update

Hi Mental Ray users and lovers,

over the course of the past 12 months, we have converted most of you, the existing and eligible Mental Ray customers, to a perpetual licensing model. That is giving you plenty of time for finishing current Mental Ray projects and for transitioning to alternative renderers in the coming years.

As some of you have noticed, the NVIDIA Licensing Portal was shut down earlier this month. That means, the option to manage your license tokens and generate license files yourself is not available any longer. We are working on a different solution that will allow you to move Mental Ray to another machine easily. We are going to announce any news here, on this blog.

Please do not hesitate to contact arc-licensing(at)nvidia.com in case of licensing issues or requests.

Happy (and uninterrupted) rendering!

NVIDIA Mental Ray for Maya 1.2.1 Update

Hi,

we have created a new build of the NVIDIA Mental Ray for Maya plugin, version 1.2.1. The primary purpose of this update is to fix a problem with the original installer, which stopped working with latest NVIDIA driver installers on Windows. At the same time, we also addressed few minor issues in the plugin itself, and in the Mental Ray core engine.

You can download the new version from our Mental Ray for Maya Forum for Linux, Windows, and Mac. This update is not auto-distributed through the NVIDIA Professional Application Center this time.

We would appreciate if you let us know that it works for you.

Happy rendering!

When the Mental Ray Installer fails…

Hi all,

we got several reports that the installation of the Mental Ray products on Windows systems may fail, or may not start at all. It turns out, that this happens when the latest NVIDIA drivers (version >390) have just been installed before the plugin.

The reason is: the NVIDIA installer framework keeps some files on the system, in order to speed up subsequent installations, and to retain a history. The latest installer version coming with the most recent drivers is not compatible with the older Mental Ray installer version, unfortunately. We are working on a fix.

UPDATE:

The latest Mental Ray for Maya installers have been fixed.
For the Mental Ray for 3ds Max installer, please try this workaround:

Rename, or remove the cache files in the directory

C:/Program Files/NVIDIA Corporation/Installer2

Then run the MR installer again. This operation will invalidate the NVIDIA installer file cache, so followup installations may need longer because starting from scratch since the installation history is lost.

Sorry for the inconvenience, and Thank You for your patience.

Steffen

Mental Ray Free Downloads

For all users and lovers of mentalray and Mental Ray (as we used to call it lately),

in case you did not notice, I have sad news: we stopped selling NVIDIA Mental Ray and the related Autodesk Maya and 3ds Max plugins end of last year. For details see Mental Ray and Iray product updates.

Fortunately, those of you who purchased licenses from us, don’t worry, you can continue to use your Mental Ray product for as long as you wish. You are eligible to convert your licenses to perpetual, just contact us by email as mentioned in the FAQ above. The same is true for schools and institutions who have registered in our Mental Ray EDU program. It’s worth to note, that the perpetual licenses are free-of-charge, and therefore do not include any support.

Even if you happen to have no license, you can still freely use the Mental Ray plugins for interactive rendering in Maya and 3ds Max, like with Maya IPR and 3ds Max ActiveShade, as well as for rendering final quality still frames in Maya’s Render View and in the Rendered Frame Window of 3ds Max.

The plugins are essential if you want to load legacy mentalray scenes in recent Maya 2017/2018 or 3ds Max 2018, to render them, or to convert them to an alternative engine, at least. But more generally, you may use Mental Ray to learn all the fundamental rendering and lighting techniques like ray tracing, global illumination, image-based lighting and much more, from the software that was/is the defining standard for a lot of these features. The plugins offer the full functionality of Mental Ray no matter if you have a license or not.

To unlock rendering of animations with Maya Batch or Backburner or Mental Ray Standalone, you need a license. We are open to giving out licenses to cover your critical and ongoing Mental Ray projects. Just let us know.

You can find the download links of the latest versions in our forum at
NVIDIA ARC Forum РMental Ray for Maya and
NVIDIA ARC Forum – Mental Ray for 3ds Max.

Happy rendering!

NVIDIA Mental Ray for Maya 2018 – now available

We just released a major update of the NVIDIA Mental Ray for Maya plugin, introducing support for the upcoming Volta GPU generation from NVIDIA using CUDA 9. If you are a user of this plugin then you should have received a notification from the NVIDIA taskbar tool. You may also download the latest version from our mental ray for Maya website.

We now introduce: Mental Ray for Maya 2018.

This is the first release of the NVIDIA mental ray plugin for Maya 2018, coupled with the matching NVIDIA mental ray Standalone. For release notes and download locations please visit our forum at Now Available: Mental Ray for Maya 2018.

Happy Rendering!

Let .mi export…

For those who¬†use mental ray Standalone to render on a remote computer or in a render farm, the creation¬†of a scene¬†file in the proprietary .mi format is a necessary step. Most content creation tools are able to¬†“echo” the full¬†scene into a .mi representation on disk using mental ray’s built-in capability. But mental ray for Maya implements a much more flexible¬†approach¬†with extra¬†functionality¬†to ease¬†render pipeline integration. In this post we would like to¬†take a closer look at some of these features.

Export Options

The mental ray export options can be opened in Maya’s¬†“Export All” or Export Selected” windows¬†by¬†sliding the separator handle to the¬†left.

options panel
Maya “Export…” Options Panel

Or, click the little options box next to “Export All” or “Export Selected” menu items.

options box
Maya “Export…” Options Box

Last but not least, the file export can be triggered and controlled via scripting, like in the Script Editor. We show an example towards the end of this post.

Export Binary vs. Ascii

Similar to¬†Maya’s ascii (.ma) vs. binary (.mb) scene formats, the .mi file can also come in¬†two flavors: ascii or binary. The binary variant is the preferred choice when the¬†precision of the scene data should be retained. The reason is, floating-point numbers are written in a binary form with no loss of bits and precision. Maya’s mental ray export enables¬†binary by default.

That’s perfectly¬†fine if you just like to feed¬†that .mi file¬†to¬†Standalone for final rendering, and not touch it. In a production studio environment this¬†is rarely the case, though. Typically, all the¬†assets (textures, materials, geometry, …)¬†are collected from¬†different sources or departments, and may¬†undergo¬†steps of post-processing and editing before passing to the renderer. The ascii version of the .mi export is often¬†better suited in such situations¬†since it allows¬†simple¬†text editing and easier scripting. On the other hand, it may result in¬†larger file sizes, and can lead to precision problems due to lossy ascii-binary conversions. There are ways¬†to solve that with mental ray for Maya. Let’s take a closer look¬†in the next sections.

Export Precision

The mental ray for Maya export engine can be tuned to use a more exact ascii conversion of extreme values that reside close to the edge of the floating-point precision range. Especially single-precision floating-point data are prone to this problem. Guess what, this is (still) most widely used to represent 3D scene geometry and transformation operations. The standard ascii conversion, which is using a maximum of 6 significant digits for single-precision values (15 digits for double-precision), can be increased up to 9 (or 18, respectively), by creating the following dynamic attributes in your scene prior to export.

addAttr -at short -ln "exportFloatPrecision" -min 6 -max 9 -dv 7 mentalrayGlobals;
addAttr -at short -ln "exportDoublePrecision" -min 15 -max 18 -dv 16 mentalrayGlobals;

Large scene dimensions and hierarchies, but also repetitive use of certain Maya modeling operations, can lead to such extreme values, see hints in the older Autodesk Knowledge Base Article.

Export File Path

A typical .mi scene contains various references to external files, like textures, finalgather maps, or output images. When rendering on a remote machine or in the render farm,¬†the directory path to these files may be¬†totally different than what was used on the exporting¬†machine. Therefore, it is often desirable to not¬†write an absolute file path into the .mi file, but just the relative one rooted at the project directory, or no path at all, and then¬†use¬†mental ray Standalone’s search path configuration on the remote computer¬†to point to the right folders,¬†or¬†shared network drives. For example, using the “-T <path>” command line option, or the _MI_REG_TEXTURE registry value.

The mental ray for Maya export options provide selective control for each type of file.

export path names
Maya Export Options – mental ray File Path

Export Filter

This section of the¬†export options allows to create¬†.mi files that only contain elements of a certain scene type, like all “textures”, or all “materials”. It translates the full scene as usual but actually writes¬†only the pieces selected in the “filter”. This way it is possible to split up a large¬†scene¬†into more manageable .mi parts that fit together perfectly. Here is an example. It will export three .mi files:

// Textures, Scene Data (zipped), Camera + Options + Render
Mayatomr -mi -file "textures.mi" -exportFilter 8388599 -xp "abs";
Mayatomr -mi -file "scene.mi" -exportFilter 1704591 -compression 1;
Mayatomr -mi -file "render.mi" -exportFilter 7699832;

The “textures.mi” file¬†contains just the textures references, all with absolute file path. The “scene.mi” file¬†carries¬†most of the¬†scene data, geometry, lights and materials, and gets¬†compressed to save disk space. Finally,¬†the last one “render.mi” stores¬†the render options, render cameras, and the final render command. Now, the first two .mi files can be included into the last one “render.mi” to¬†create a renderable “master” .mi file, see this¬†.mi¬†snippet:

    ...
$include "mayabase.mi"

$include "textures.mi"
$include "scene.mi.gz"

options "miDefaultOptions"
    ...

The resulting .mi file can be given¬†to mental ray Standalone for final rendering. Arrgh, I got a new version of one of the textures last minute!¬†Well, no problem! Just update¬†the “textures.mi” file, no need to touch any of the heavy data. And re-render. Voila!

While this works great in general, it does not¬†help the renderer to load certain scene parts on demand only, like when it is actually “seen”¬†during rendering. That’s where¬†mental ray “assemblies” come into play.

Export Assembly

This export option helps to create a valid mental ray “assembly” from a Maya scene. It writes¬†a normal .mi file¬†with a few¬†special properties. A¬†mental ray assembly is used to¬†store a larger part¬†of the scene that belongs together spatially, like a character or a whole building. Normally, it¬†comprises the geometry details of the sub-scene and related local properties like materials.

Maya Export Options - mental ray Export Render Proxy (Assembly)
Maya – mental ray Export Assembly

Model courtesy Lee Anderson.

Such a .mi file can be referenced from a “master” scene¬†“stand-in” bounding box object, which defines the ultimate¬†location and scale in the global space.

load assembly
Maya – mental ray Load Assembly

In contrast to Maya file references, such an assembly is not loaded or shown in Maya immediately, thus not filling up memory and impacting your modeling operations. Instead, mental ray will load these parts only on demand during rendering, and even unload the piece in case room for other assemblies is needed. This mechanism enables the renderer to handle massive amounts of scene elements more efficiently, and keep memory consumption under control. The resulting rendering is no different to a regular render.

maya render view
Maya Render View – mental ray

Model courtesy Lee Anderson.

If you like to build a scene that contains huge amounts of similar looking¬†objects that can share the actual assembly geometry, we suggest to use instances of the same assembly rather than copies (!) (which is the default “duplicate” operation¬†in Maya). The placement and scale of the stand-in “proxy” element referencing the assembly determines the final location and size in the final rendering.

maya model view - mental ray assembly instances
Maya Model View – mental ray Assembly Instances

mental ray assembly instances
Maya Render View – mental ray Assembly Instances

This technique of using mental ray assemblies is also available to shader writers and integrators through the programming API. In fact, it is utilized¬†in the mental ray implementation of crowd simulation engines like Massive for Maya, or Maya’s native procedural generator XGen, to handle incredible amount of elements.

We hope these tips will help you in your daily work.

BTW, there are more possibilities to tweak .mi file export even further (“text boxes”). But they are rarely used, and would justify another blog post¬†in case there is interest. Just let us know.

Happy rendering!

I am on a Mac, and use mental ray for Maya. But…

Hello Mac users,

you love to stay on your Mac and use mental ray for Maya?

No problem, since Maya offers the same Qt user interface and experience¬†like on Windows or Linux. Maya scene files and mental ray .mi files that have been generated on other platforms can simply be used on the Mac. Even the configuration files, “Maya.env” and “maya.rayrc”, work identically. All true, but…

Several¬†things are different. For example,¬†the unique¬†use of¬†Mac specific keyboard shortcuts is puzzling, like¬†in the “open scene” window. Switching to the “OS native” file dialog is possible in the¬†Maya preferences. Although it¬†might even be more confusing to use Qt and non-Qt side by side.

What about mental ray ? Well, it is only dependent¬†on the underlying Unix basis¬†“Darwin”¬†with its stable and standardized interfaces. That keeps it quite independent from frequent¬†Mac OS X updates, which¬†typically just touch the application levels of the operating system.

Normally. But the most recent “Mavericks” update of OS X, version 10.9, seem to have changed some¬†multi-threading behavior of the kernel. mental ray is obviously also affected, and shows unexpected interruptions, or even gets blocked completely during rendering. Our developers¬†are currently¬†diving¬†into it, to come up with a solution as soon as possible.

Here is another little annoyance:

The message log for¬†mental ray preview rendering has disappeared a few Mac OS X versions back, also due to a system change that¬†handles console output. The¬†batch rendering is not affected since it writes the messages to¬†a¬†file. There is a workaround for preview rendering, though, using mental ray for Maya’s¬†built-in log facility that works separately to the system log. It can be enabled on the Maya command line like this (also¬†useful for a Shelf button):

Mayatomr -preview -log

It will create a file with the fixed name “mentalray.log”, typically residing in the last opened scene file directory. Double-clicking on the file in the Mac Finder will open the Console App, giving a similar experience to the message display on other platforms. If you enable the Console preference “bring log window to front” it will pop up automatically with each mental ray rendering of that scene using the -log command.

mental ray messages
mental ray for Maya log messages

Happy rendering!