Deep OpenEXR files allow to store a variable number of samples per pixel at different depth locations to aid advanced depth compositing workflows.
To render a Deep OpenEXR file with mental ray, open the Render Settings dialog and make sure that the image output format is set to “exr” in the Common tab:
In the Scene tab, enable the “Use Deep Image format” checkbox:
The Deep OpenEXR file is written in multi-part, which means that files can contain a number of separate but related images. Each render pass gets its own part (i. e. direct_diffuse, indirect_diffuse).
In order to save memory during rendering, mental ray creates tiled Deep OpenEXR files. These files need to be converted to scanline for use in compositing applications like Nuke. This conversion can be performed using imf_copy, a command line tool that is part of your mental ray for Maya installation. It can be found in the bin directory. Call
to perform the conversion. Click on the image below to see a screenshot of the tool executed on a Windows system:
Please note that currently only z front is supported. This means that rendering deep volumes is not possible yet. Deep and flat data cannot be mixed in the same OpenEXR file.
mental ray for Maya 2016 SP2 is now available for download here or it is automatically installed by the Autodesk Application Manager.
It ships with mental ray 3.13.1.9 which contains improvements for the BSP2 acceleration structure in certain cases, bug fixes for multi-host rendering and for some framebuffer handling issues. The release notes provide more details.
Several bugs were fixed in the mental ray for Maya translator, notably concerning undo when modifying simple mila_material parameters, satellite rendering issues, and a workflow improvement with regard to the new Create->Lights menu and Environment lights.
mental ray for Maya 2016 SP1 is now available for download here.
It ships with mental ray 3.13.1.8. Both the mental ray core and the integration provide important fixes that we will list in this post.
MDL rendering: latest MDL fixes are incorporated into SP1.
The new version of the MILA layering shaders fixes various issues:
alpha channel computation for specular and glossy transmission
possible texturing artifacts if mila_light light shader was used
halo effect on specular highlight when using mila in IPR
possible black pixel artifacts / NaN warnings in custom curve layer weights
unknown tag access fatal if mila_specular_transmission was used in combination with irradiance particles or with the GI Next prototype
possible issues with semi-transparent objects in segmented/sorted shadow modes
possible tile artifacts in particular with glossy reflection mix
VP2 display for mila is now also working for scenes created with Maya 2015
UV-tiling: There was a severe bug around uv-tiled textures and conversion to .map textures: the conversion to .map would sometimes be automatically triggered. This is fixed now. The conversion will only occur if ‘Use optimized textures (auto-conversion)’ is checked in the rendering preferences. (There is a known issue in this context: the button ‘Update optimized cache textures now’ only converts the first uv-tile of a uv-tile sequence. The others will be converted during the first rendering.)
Also, when you created two file texture nodes both referencing the same uv-tile sequence, this could lead to a crash with the previous version. This is now resolved.
There are also various performance improvements in the SP1 version:
Since Maya2016, the new shadow mode default is “shadow segments”. This mode supports all ray tracing effects including subsurface and volume scattering in contrast to the approximate, thus potentially faster “simple” shadows. With the latest mental ray, we have improved the performance of “shadow segments” on scenes with extremely high depth complexity.
Light Importance Sampling is now faster for scenes with a mixture of large and small are lights.
Mental ray render times with procedural shaders/textures (ocean, fractal, and so forth) are also improved.
In this second post in a series on mental ray for Maya 2016 Render Settings, we assume you are familiar with the concepts presented in the introductory post.
Adjusting Overall Quality
Overall quality is the primary control for adjusting quality vs. speed. When there is noise in the scene, typically increase this quality.
In our example scene below, we set Overall Quality to an extremely low 0.01. Please note the edge aliasing on the tops of the spiral cone object. The back wall also has a bump texture which has noise at this quality setting.
Overall Quality 0.01
In the following images we increase the overall quality from 0.2 to 1.0 by 0.4. Note the better anti-aliasing at the edges of these objects, in particular.
To visualize how eye ray samples were placed in the rendered image, from the Diagnostic tab check Diagnose Samples before rendering. With this checked, each render creates special informational passes for diagnostics including samples, error, and time per pixel. To view it, from the Render View File menu in Load Render Pass, choose the Diagnose samples pass.
This will bring up an imf_disp window with the samples pass already tone-mapped to see the sample density in gray scale clearly.
Note the green arrow above pointing out useful information in the bottom bar. Wherever you locate the cursor on the image, in this bar you will see the pixel location, [202 48], and the number of samples, 15 in this case.
Here are a set of samples diagnostics to match the increasing quality from our scene above from 0.2 to 1.0. Whiter areas have more samples.
Balancing Quality Adjustment
Although Overall Quality can be used to handle most quality vs. speed adjustment, we can provide understanding how to get to desired results more efficiently. Understanding is important to prevent artists from quick fixes that turn out to take longer than originally planned.
With that said, it is possible to balance the local vs. the global quality settings for faster renders. This balance will evolve as machine resources change and rendering technology adapts. For example, a brute force render running on GPU might rely solely on a global quality control, since pure path tracers do not split eye rays by design. However, current mental ray provides flexibility in how much you want to tip this balance one way or the other. It can evolve at your pace, and fit your CPU and GPU resources as they evolve.
Use the localquality controls when there is an unbalanced amount of noise from lighting or from materials. For example, if the direct lighting appears to create more noise than other aspects of the scene, increase the lighting quality for optimum speed vs. quality tradeoff. Once adjusted, the overall quality can be used as the main control again.
Consider lighting quality adjustment when the lighting has a large variation. For example, when using a large (> 40) number of lights, or several large area lights. Or when using a high resolution, highly varying HDR image for your light texture. For example, below we have one rectangular area light showing its HDR texture clearly as not uniform. Its range reaches up to values of 70 in a thin horizontal line in the middle of the thick one you see at this exposure. It required less light intensity as well as high lighting quality.
Consider indirect diffuse or material quality adjustment when noise appears on indirectly lit diffuse or glossy surfaces. Or on surfaces with a lot of geometric detail. If you ever had to work with an ambient occlusion (AO) pass that needed more samples, you have a rough idea of the kind of look difference due to geometric variation. The surface details can come out a bit more clearly, with less noise.
Adjusting Lighting Quality
The Lighting Quality controls the number of direct light samples used, when a ray hits an object. It takes into account the number of lights, both point and area, and other factors to determine how many light samples to use.
The scene used for our example has 14 area lights with sphere shapes. Note the quality of the direct lighting on the floor as we increase lighting quality. In this series, we keep Overall Quality at 0.25 and increase Lighting Quality from 0.2 to 1.0 by 0.4 steps.
When using Lighting Quality in the new UI, mental ray overrides the explicit area light samples set in each area light with a global samples-per-light setting. (Currently, it does not gray out the samples settings in the area light AE UI). The total number of light samples are re-allocated based on importance. For example, more samples may be taken from closer, or higher intensity, lights.
Tip: If you are having difficulty isolating the visual noise for adjusting direct lighting quality, use MILA light passes to help you see it. In the Scene tab, enable the direct diffuse pass and adjust to minimize noise in that pass, compared to other passes or the beauty itself.
For example, the following images show the direct diffuse pass from the above renders, as Lighting Quality increases from 0.2 to 1.0 by 0.4 steps.
We will show more detail about light passes in our upcoming post on light passes.
Environment Lighting Quality
Controls the number of environment light samples to use. Also using importance, it is separate from lighting quality and enabled when environment lighting is enabled. We will give examples of this in a later post in this series about environment lights.
Adjusting Indirect Diffuse (GI) Quality
We encourage the selection of On (GI Prototype) mode, over Finalgathering and other legacy modes, for its reduced controls and higher quality. When On, mental ray uses a new technique to characterize arbitrary material shaders, while also providing non-interpolated brute force sampling paths for ease-of-use.
The Indirect Diffuse Quality controls the number of samples split out for a diffuse interaction at a material. For the basic default Global Illumination (GI) mode of On, this controls the number of GI rays. In Finalgather (FG) mode, it controls the number of FG rays, as well as the FG point density and other FG controls.
Below as Indirect Diffuse Quality is increased, note the noise on the floor where the light has to reach from reflections off the walls, ceiling and objects.
To see it isolated as we did above with the direct diffuse pass, enable the indirect diffuse pass.
Diffuse Trace Depth
The Trace Depth controls affect how deep an individual eye sample path can go. The Indirect Diffuse trace depth has moved into the general Trace Depth section. When an eye sample originates from the eye, each interaction along a given path increases the ray traced depth count. The interaction type can identify different types of counts. For example, a Diffuse reflection or transmission counts toward the Diffuse depth, while glossy or specular reflection counts toward Reflection, and glossy or specular transmission counts toward Refraction.
Note: Currently, a Diffuse value of 0 means that the first indirect diffuse samples are taken, but then no others, when an indirect diffuse mode is enabled. In other words, the act of using an indirect diffuse mode automatically creates the first level in trace depth. However, this diffuse count starts after the first diffuse interaction, not at the eye. Compared to the rest of the depths, this means this number is one less in relative depth to the other interactions for a given eye sample. This matches legacy FG diffuse depth control. But this will be changed in the future to better match the other trace depth controls.
Material Quality is discussed in more detail in the next post on recommended modern materials and lights.
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.
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”.
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:
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:
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:
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
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:
When 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.
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.
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_3dsMaxinto 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:
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:
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:
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.
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.
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.
When 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.
We 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.
Traditionally, 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.
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.
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.
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.
mr Ambient Occlusion Render Element
mr 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.
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”:
Render Element “iray: Irradiance”
Irradiance 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:
Inside mental ray 