Using MDL with mental ray for Maya 2016

In Maya 2016 we are introducing basic support for loading and rendering MDL materials with mental ray. In this post we want to take a closer look at how these materials can be used in Maya. For a general introduction to MDL in mental ray, check out this post.

Prerequisites

Before starting to use MDL materials in Maya, we recommend to update the library that is used by mental ray to process MDL. Please download this archive, extract it to a temporary directory, choose the file suitable for your platform and replace the libmdl.dll (libmdl.so on Linux, libmdl.dylib on Mac) in the bin directory of your mentalrayForMaya2016 installation with the new version. On a Windows system, this is typically in C:\Program Files\Autodesk\mentalrayForMaya2016\bin (see image below), on a Unix system it is /usr/autodesk/mentalrayForMaya2016/bin and on MacOS /Applications/Autodesk/mentalrayForMaya2016/bin.

mental ray bin location on Windows

The MDL Node

In Maya, MDL materials are represented by a new surface shader node called mdl_material, which is located in the mental ray surface material section of the “Create Material” window or “Hypershade”.

Create MDL material node

When you assign an mdl_material to an object, you will see that it contains two drop down lists: One for choosing an MDL module and another one for choosing an MDL material:

mdl-material-property-view

An MDL module is a file which can contain one or more MDL materials and has a “.mdl” extension. By default, mental ray for Maya 2016 ships only one module, that contains the default_material, a light grey diffuse. Because of that, both drop down lists contain just one entry.

To populate the lists you will need more materials. In the next section, we will see how to get some.

Adding MDL materials

As already announced in the MDL introduction post, example materials can be downloaded here.

1) Unzip the archive to a temporary directory.

By default, mental ray for Maya uses one root directory for placing MDL modules, the directory shaders/mdl within your mentalrayForMaya2016 installation.

2) Copy the folder mdl_examples_for_maya_3dsmax into the MDL root directory as shown below:

mdl-directory

If you do not have write permissions in the Program Files directory or would generally prefer another location, you can define additional MDL root directories by specifying the MI_MDL_PATH. To do so, open the Maya.env file, which can be found in the Maya 2016 user directory:

maya-env

Add the line

MI_MDL_PATH=<Path to MDL files>

If you, for example, make an MDL root directory called “mdl” in your Maya/2016 user directory, as shown in the screenshot above, your MI_MDL_PATH path needs to look like

MI_MDL_PATH=C:\users\<USERNAME>\Documents\Maya\2016\mdl

More than one path can be specified, separated by a “;”.

A note on packages

In most cases, MDL modules are organized into packages, just like our example package. On disk, a package corresponds to a directory. The name of the package is the name of the directory. Packages can be nested to organize complex libraries. Within a package, modules can reference each other and contained resources (like textures) relative to each other or the package root directory. Because of this, it is important to always retain the package structure. Never just copy single mdl files or subdirectories out of a package into your MDL root directory, always use the full package, including the root folder.

Rendering MDL materials with mental ray for Maya

Now that our example package has been put into place, start Maya. Create an object and assign a mdl_material to it. The MDL Module drop down list should look like this:

Example PackageWhen you choose a module, the material drop down list will be populated with the materials contained in the selected module, and the first material will automatically be selected. The “MDL Material Parameters” section shows the parameters of that material, which you can modify to your liking.

mdl-with-render

Other MDL materials, focused on requirements from the automotive industry are available for download in the Advanced Rendering Forum.

Limitations

MDL materials are closed entities. They cannot be used in a shading network. Even though Maya allows connections to traditional shader and utility nodes, mental ray will ignore these  connections. However, MDL materials can be used alongside with traditional materials and shaders.

In its initial state, the mdl_material node does not come with a swatch render, has no viewport representation and is also not supposed to work with IPR. These limitations will be removed in future releases.

Using MDL with mental ray in 3ds Max 2016

Following the introduction, we will now go through the steps to render MDL materials in 3ds Max 2016. In the instructions below, [3dsMax2016] referes to the folder where 3ds Max 2016 is installed (typically C:\Program Files\Autodesk\3ds Max 2016).

Installation

1. Unzip the attached package NVIDIA_MDL_3dsMax into a temporary folder.

The package NVIDIA_MDL_3dsMax.zip contains the following files:

  • mdl_examples_for_maya_3dsmax.zip – Archive with mdl examples
  • libmdl.dll  –  Latest version (3.13.1.8) of the MDL mental ray dll
  • mdl_max.mi  –  GUI file to display pretty MDL names
  • MDLScene.max  –  Sample 3ds Max scene with MDL materials

2. Unzip mdl_examples_for_maya_3dsmax.zip into a newly created folder  [3dsMax2016]\NVIDIA\shaders_3rdparty\mdl\

You should end up with the following files:ExplorerViewOnMaxMdlExamples

3. Install the file mdl_max.mi in the folder [3dsMax2016]\NVIDIA\shaders_autoload\mentalray\include\

4. Copy the new version of libmdl.dll into the folder: [3dsMax2016]\

 

Rendering in 3ds Max 2016

Start 3ds Max 2016, chose mr production renderer and open material editor. You should see a new set of materials:

mtls

You might want to load the scene MDLScene.max, it has some MDL materials already set.
Here is mental ray rendering with few MDL materials assigned:

mr

And iray rendering:

iray

NVIDIA Material Definition Language (MDL) with mental ray

NVIDIA Material Definition Language, in short MDL, is an NVIDIA initiative to standardize physically based material designs in a common format, see www.nvidia.com/MDL. MDL materials can be shared across renderers which are able to handle physical material properties like BSDFs in their core. mental ray 3.13 offers support for rendering pre-packaged MDL materials. In this post, we provide links to resources for MDL and give some background. In the following posts, we give instructions on how to use the materials in 3ds Max and Maya and provide example MDL materials.

The Material Definition Language Handbook gives an in-depth introduction to MDL and is aimed at the technically interested reader to learn more about the concepts of MDL and the ideas behind it. It’s work in progress and you will see it evolving over time. In the MDL developer section, you will find the MDL Technical Introduction and the MDL 1.1 Specification among other information.MDL materials rendered with mental ray

In this first version of MDL in mental ray, the user should expect some restrictions that we will remove going forward. Editing MDL materials is currently only possible on a parameter level after loading external MDL code through the mechanism that we describe below. Both MDL materials and traditional shaders can be utilized side by side within the same scene and will render smoothly. However, MDL materials are closed entities for mental ray upon loading. Parameter connections to other shaders or other MDL materials are currently not supported. Measured materials and the emissive properties of MDL are not yet handled by mental ray 3.13.

We are providing some MDL material examples in the subsequent posts that showcase the power of MDL for rendering complex shading and lighting effects. Please follow closely the instructions on how to install the examples for rendering within your application.

Introducing mental ray for Maya 2016 Render Settings

This is the first in a series of posts on mental ray for Maya 2016 Render Settings

Introduction

We significantly changed the mental ray for Maya 2016 Render Settings User Interface (UI) in order to reduce time spent adjusting renders. The defaults aim for no-fuss rendering of the most frequently used and up-to-date features. Of specific note, our newest Global Illumination (GI) mode significantly increases ease-of-use and productivity.

We provide almost everything a user needs here within this UI. For example, a user should not have to type in string options anymore.

Goals

Members of both NVIDIA ARC and Autodesk, including UI designers and developers, collaborated to make this change significant. As stated in the Maya 2016 documentation for mental ray Render Settings, we aim to:

  • Enable complete rendering without requirement to adjust or enable most settings. The defaults should enable the most frequently used features.
  • Increase ease-of-use when adjusting settings to control for optimization and quality.
  • Provide single global controls to reduce repetitive and potentially error-inducing settings across scene elements.

We also want to retain the flexibility of mental ray for production users. So we provide an Advanced Settings option on each of the new tabs. We hide less frequently used features in favor of a cleaner, more productive and simpler control for basic workflow. This leads users of all levels to what is fundamentally important to control.

Render Settings Tabs

We re-organized the mental ray Render Settings into four main tabs:

The Quality tab contains quality settings for controlling sampling. By using quality settings, instead of sample counts, we take advantage of better optimization schemes internally. We also believe it will be conceptually easier, once the community gets familiar with this style of control.

The Scene tab contains shared settings across scene elements, such as camera settings that should be applied to all renderable cameras. This is where we provide the new simplified mental ray Passes.

The Configuration tab contains settings that are more likely to be used across Maya sessions, and how a user likes to work with the scene. For example, the interactive rendering control for progressive rendering depends on a machine’s resources.

The Diagnostics tab contains settings that help a user with problem solving, or identification of areas for optimization.

Quality Settings

Here, we provide an overview of how to adjust your scenes with the new UI, suggesting our recommended practice.

For new scenes, use the Overall Quality setting in the Sampling section as the primary control for speed vs. quality. It is located at the top of the Quality tab.This controls samples across a scene. Samples are not fixed per pixel. Rather, they vary in density per pixel region. More samples are taken in each region until the quality is matched.

In the next section, we provide detail to better understand how to adjust quality beyond the Overall Quality setting. With better understanding, we hope you can more quickly achieve your desired results. 

Understanding more about quality adjustment

Here, we introduce the concept of global vs. local sampling. This concept is key to adjusting quality now and in the future, as rendering technology evolves.

The Overall Quality setting is a global setting that controls samples across a scene. Each sample starts a ray traced from the camera out into the scene. In essence, we sample the scene from the eye (E). Below, we show an eye ray (in green) over a work by Albrecht Dürer.

durerWhen an eye ray intersects an object, the eye ray may split into several samples. We will call those the local samples, in contrast to the global samples, because they are local to each eye ray. Below, we show a diffuse distribution of local samples split out for diffuse reflection.

eye_rayWe separate the local samples into two categories at an intersection point: the samples used for lights and the samples used for materials.

For materials, the sample directions depend on the type of surface at the intersection point. For example, above a diffuse surface creates samples in the hemisphere above the intersection point. Because these samples tend to hit objects, it represents indirect light.

For lighting, the samples are taken from all visible lights in the scene. Below, we see a single light sample for the same intersection point. There could be more light samples depending on number and size of lights. Light samples represent direct light.

light_rayTraditionally, lights were only those elements specified explicitly as lights in the scene, and they had no size. However, as rendering implementations evolved, so did lights, from point to area lights, and now, emissive objects. Also, consider the light from an environment. Environments convert automatically into light sources by enabling environment light emission. When enabled, we provide a separate quality control for the environment lighting.Note that it is grayed out when not enabled. Furthermore, now one can create such a light more directly. See for example Create > Lights > Environment Image (IBL).

Similarly, we provide a separate control for indirect diffuse (GI) quality in materials, even though it is conceptually a part of material quality.As global illumination techniques have evolved considerably, so have the ways to control these techniques. Yet, the Indirect Diffuse Quality applies to any Indirect Diffuse (GI) Mode selected, and to any material used.

In our next mental ray for Maya 2016 Render Settings post, we provide more details and examples for Adjusting Quality.

Light Path Expressions Improvements in 3ds Max 2016

Starting with iray in 3ds Max 2015 you can render different bits of information into different buffers using Light Path Expressions (LPEs). LPEs are exposed through iray Render Elements.

LPEs are regular expressions that match some light transport paths that iray generates. Each result buffer can be associated with an LPE so that only paths which match the expression end up contributing to that buffer. The iray renderer also allows you to render several buffers with different LPEs at the same time at almost no additional runtime cost. LPEs can distinguish between different surface properties such as diffuse or glossy, reflection or refraction, types of light sources, and names.

In 3ds Max 2016, LPEs have been extended to allow light-specific and object-specific paths.

Light-specific LPEs allow to render your scene per light source. You can then adjust light intensities in a post process, weighing them together.

Object-specific allow to render your scene per object. You can then perform artistic compositing of an image, for example by subtracting an object’s reflection from the beauty image or by adding glow to the image.

For examples of LPE usage, check out these iray blog posts:
Compositing with Light Path Expressions
Instant Relighting & Nonphysical Effects
Get a grip (2): instant color change

Lights and objects need to be grouped into layers before they can be referenced in LPEs.

Below is an example how to achieve this. You can download the example scene from https://s3.amazonaws.com/arcdownload/irayLPESceneUsingLightsAndObjectsHandles.zip.

Open “Tools/Layer Explorer…” to group objects (e.g. the cosmetic box below is under a layer named “container”):


Grouping geometry in the Layer Explorer

The “container” can then be referenced in an LPE "L.*'container'RE" (reflections of the cosmetic box):


Creating an LPE with object-specific path

containerreflectionsRendering "L.*'container'RE"

In the same way lights can be grouped into layer and referenced in an LPE:


Creating an LPE with light-specific path

right_lightRendering "<L'light_right'>.*E"

Hope you will find this post useful.

mental ray for 3ds Max 2016

Here is an overview of the mental ray and iray features which were integrated in 3ds Max 2016.

NVIDIA Material Definition Language (MDL)

The Material Definition Language (MDL) is an NVIDIA initiative to standardize physically based material designs in a common format, see http://www.nvidia.com/MDL. mental ray for 3ds Max 2016 is capable of rendering pre-packaged MDL materials. We will create a dedicated blog post to explain how to enable MDL in 3ds Max 2016.

mdl_examples_3dsmax Rendering MDL with mental ray

Light Importance Sampling (LIS)

The new Light Importance Sampling mechanism in mental ray allows to sample the whole set of lights as if it were one single light, placing more samples on the lights that contribute more to the part of the scene being rendered. It is an importance-driven mechanism that is controlled by a simple set of parameters. Both area and point lights are importance-sampled, and there is no fundamental change required in material and light shaders. This mechanism is typically useful in scenes with many lights, but can be beneficial also in other simpler cases.


Light Importance Sampling parameters

Ambient Occlusion, GPU accelerated

mental ray offers a new, efficient, GPU accelerated “mr Ambient Occlusion” render element.

aomr Ambient Occlusion Render Element

aoparmsmr Ambient Occlusion parameters

The “Max Distance” controls the maximum distance of occlusion probe rays (Note: Value 0 for “Max Distance” means infinite distance). “Falloff” controls how much the occlusion fades out with distance.

Displacement Settings

The mental ray and the iray renderers now offer the “Parametric” approximation method which can help to troubleshoot scenes where the “Length” method exhibits artifacts, for example scenes with very regular and flat geometry. This method is available from the “Render Setup/Renderer” tab and from the “Object Properties/mental ray” tab.


Object Properties/mental ray tab – Displacement Settings

The parametric approximation method regularly subdivides each triangle of the surface. The “Subdivision Level” specifies how many times each input triangle should be subdivided. A higher “Subdivision Level” results in a higher triangle count. Each input triangle is subdivided into 4(Subdivision Level) triangles. Note: there is an internal limit of 8 million triangles per object.

Section Plane

The iray renderer offers a new helper object “iray Section”. The “iray Section” behaves similarly to the “Grid” helper and is used to cut off the geometry in the rendered image. Section planes can either cut off the geometry completely (so let the light in), or let the viewer take a peek inside, see “Clip Light” parameter. You can define up to 8 section planes.

sectionplaneiray Section Plane Helper

Texture Compression

The iray “Texture Compression” can save around 75% of texture memory on both CPU and GPU. This is enabled by default. See http://blog.irayrender.com/post/54506874080/saving-on-texture-memory for details, the level of compression exposed in 3ds Max 2016 is the “medium”.

texturecompressionTexture Compression parameters

Light Path Expressions Improvements

Light Path Expressions (LPEs) for iray have been extended to allow light-specific and object-specific paths.

Lights and objects need to be grouped into layers before they can be referenced in LPEs.

We will create a dedicated blogpost to explain this mechanism.

Irradiance Render Element

The iray renderer offers a new Render Element “iray: Irradiance”:

irradianceRender Element “iray: Irradiance”

irradiance_parmsIrradiance parameters

It is recommended to turn off tone mapping when computing irradiance. By default the irradiance buffer is converted to a heatmap, displaying the lux (or footcandle) values with false colors:

irradiance_bufferRendering Irradiance with heatmap on

Auxiliary Buffers Render Elements: Alpha, Normal, Depth

The iray renderer also offers auxiliary buffers Render Elements (Alpha, Normal and Depth):

auxiliaryAuxiliary buffers Render Elements

auxiliary_buffersRendering Auxiliary buffers

Here is for the tour of the new mental ray and iray features integrated in 3ds Max 2016.

Hope you will find this useful.

Pascal

mental ray for Maya 2016

In this post, we introduce the newest features of the mental ray for Maya 2016 plugin that is delivered with Autodesk Maya 2016 and can be downloaded here. Stay tuned for more in-depth posts on the features.

Render Settings Redesign

This version comes with a complete new layout of the Render Settings. Our goal is to make the rendering experience with mental ray straight forward and easy. Settings are greatly simplified and grouped together. Five tabs allow to find settings sorted by topic. For advanced users, each tab provides the ‘Advanced Settings’ mode with more detailed controls to fine-tune the rendering.

newRenderSettings

The Scene tab contains a simplified render passes system for standard utility passes

newRenderStandardPasses

as well as MILA Light Path and Matte Pass passes.

newRenderMilaPasses

A more throrough introduction to the new Render Settings will follow shortly.

NVIDIA Material Definition Language

mental ray 3.13 renders materials defined by the NVIDIA Material Definition Language (MDL). MDL is an NVIDIA initiative to standardize physically based material designs in a common format, see http://www.nvidia.com/MDL. Prepackaged MDL materials can be applied in mental ray for Maya 2016. We will provide you with an introduction on how to use MDL in Maya 2016 and with examples for download in this blog soon.

mdl-spheres

Light Importance Sampling By Default

Light Importance Sampling is now enabled by default. It gives a significant speed / quality advantage out of the box especially with modern and complex lighting setups, emissive objects, and very many light sources. In addition, new heuristics have been incorporated that automatically determine which light sources in the scene are physically plausible and would benefit from importance sampling. This way, traditional idealized light sources and simple lighting setups can be detected and handled separately, like they may be excluded from importance sampling to retain an overall benefit even though this feature is generally enabled. Custom light shaders are fully supported and will be included in importance sampling if they adhere to physically plausible emission and distribution rules.

Deep OpenEXR

mental ray 3.13 adds support for generating ‘deep’ data and output to OpenEXR files. The resulting image is saved in the DeepTile form of the OpenEXR 2.0 file format, storing additional information of the pixel colors along the Z axis. It is possible to save deep and simple 2D data into different frame buffers during the same rendering.

UV Tiles Optimized

Rendering UV-tiled textures is faster and more memory efficient in this version because it is based on a native mental ray shader. It auto-creates and loads the tile textures into mental ray on demand, making sure that only those tiles that are actually accessed get loaded into memory. The shader is part of a new package called coreutil, which collects essential mental ray utilities and helper functions.

Create Lights menu 

There is a new section in the Create|Lights menu for mental ray lights showing modern mental ray lights in a prominent and easily accessible place.

createLightMenu

Object Lights

Using custom geometry to light your scene is now possible with mental ray for Maya 2016. You can assign the new ‘Object Light’ material to your geometry or, with the geometry selected, you can choose ‘Object Light’ from the new mental ray section in the Create|Lights menu. This will turn your geometry into a light.

 light_bulb_cropped

                           Light bulb model courtesy of David Hackett.

Rendering Bifrost with mental ray

Bifröst is a procedural framework that can create simulated effects ranging from liquid to foam, bubbles, spray and mist. These effects can be rendered using the bifrost geometry shader delivered with mental ray for Maya 2016.

Autodesk published videos on bifrost and showing mental ray rendering at the end of each:

Maya 2016: Adaptive Aero Solver in Bifrost
Maya 2016: Guided Simulations in Bifrost
Maya 2016: Adaptive Foam in Bifrost

XGen hair shading and displacement

Rendering XGen with mental ray has been improved and enhanced with new features.

The default XGen hair shader for mental ray is now xgen_hair_physical. It is based on the mental ray human hair shader mib_illum_hair_x which has been improved with mental ray 3.13. It now adds contributions from indirect lighting to the shading. New parameters have been added to tune the tube shading look and to control the internal color noise effect.

Displacing sphere and dart primitives is now possible allowing for a much wider use-case for these primitives.

xgen-spheres-with-displacement

Texture Filtering based on Ray-Differentials

For advanced ‘elliptical’ texture filtering in Maya’s file node, we are now using ray differentials provided by mental ray core. This introduces more accurate and artifact-free texture filtering even across ray traced reflections and refractions.
To enable it, select a file node, choose ‘Mipmap’ as filtertype, go to the mental ray section and enable ‘Elliptical filtering’. You can choose between ‘Bilinear’ or ‘Bicubic’ filter mode.