NVIDIA Iray Making headlines - again!

Dec 23, 2015 at 11:36 pm by nickcharles

NVIDIA Iray® is now available as a plugin renderer sold directly to consumers for Autodesk 3DS Max and Autodesk Maya. Iray for other products, including Autodesk Revit and Rhinoceros will be out soon! I had the chance to play with the latest version of NVIDIA Iray for Autodesk Maya through the NVIDIA Iray beta testers program.

Iray comes with a 90-day free trial. Anybody can test drive it! Stop reading and go play with it!

What is NVIDIA Iray?
NVIDIA Iray is a physically based 3D renderer in the same vein as something like Mentalray, but with significant differences. Iray is physically based in that it relies on Bidirectional scattering distribution functions (BSDF), Emissive Distribution Functions (EDF), and Volume Distribution Functions (VDF) for computing light paths. Quite simply, most of the pretty settings are automatic: E.g., Indirect illumination, color bleeding, reflections, refractions, soft shadows, blurry reflections, reflective and refractive caustics, volume scattering, etc. You just assign materials and click render. All the rest pretty much takes care of itself.

iray loft
Image courtesy Nvidia.

Iray offers two modes: Iray Interactive, designed to be faster and 'good enough' and Iray Photoreal for those demanding shots that require the highest physical accuracy.

Image courtesy Nvidia.

What sets Iray apart is it's implemented in Nvidia CUDA. Therefore, Iray takes full advantage of NVIDIA Quadro cards including those based on Fermi, Kepler and Maxwell cores. You can even mix and match multiple GPUs from different generations in the same machine and Iray will utilize them all.

Iray targets architectural designers, product designers and other artists who need near push-button photorealistic renders on a deadline. It does this very well. Simply turn on Iray photoreal, assign materials, click render and for the most part you're done. As long as you get your materials right, there's not a lot of fussy to worry about. Iray takes care of itself.

Image courtesy Nvidia.

The other nice part about Iray is the responsive workflow. You can fire up the Iray IPR in Autodesk Maya (either with interactive or photoreal mode) and, given a beefy enough GPU, you can arrange your lights and tweak shader attributes and get rapid, high-quality feedback in the render window. No more guessing settings and waiting forever to see if you guessed correctly. Given compatible hardware, interactive feedback with Iray is significantly faster than other renderers. (Everything that works in the renderer, works in the IPR, including translations, deformations, moving the camera, etc.)

How is Iray different?
For starters, Iray can take full advantage of CUDA to dramatically accelerate the rendering process. With Iray this is not a piecemeal approach to GPU acceleration. Instead, Iray was designed from the ground up for CUDA - even across multiple GPUs.

While Iray makes no attempt to be a real-time renderer like OpenGL or DirectX based technologies, given enough hardware, Iray can actually become real time as is the case when using an NVIDIA Quadro VCA, but more on that later.

Image courtesy Nvidia.

Iray scales. It can utilize all CPUs and CPU cores of even a multi-socket system and all CUDA cores on all NVIDIA GPUs. Iray can even connect over the network to an Iray Server (a separate product) or an NVIDIA VCA. The more hardware you throw at Iray, the faster it renders. It's like the Borg of renderers. It's licensed at a flat annual rate per host system, not per core or per GPU. It's even priced so mere mortals can afford it. This is a very good thing!

Working with Iray was fun. I could turn on the IPR and watch the progressive render take place as I worked. The image starts out grainy but converges until a user-defined threshold of quality is met. This threshold can also be specified as a maximum time permitted to render and Iray will provide its best effort in the allotted time.

Image courtesy Nvidia.

With fast enough hardware Iray gets really fun! You can model or arrange your scene while leaving the IPR window open and watch Iray in near real time re-render your scene. This is great for getting a caustic or a reflection in the right spot or tweaking lights, material parameters or even just move and deform objects, etc. Iray IPR is constantly rendering, yet gives you control over what resources Iray is permitted to use. For instance, you can disable Iray on parts of your machine to strike a balance between Autodesk Maya interactivity and Iray rendering performance.

Iray will make use of multiple GPUs from multiple generations including Fermi, Kepler, and Maxwell.

With Iray, I was far more productive than with other renderers I'm used to. Being able to instantly see changes update in the render view, even if grainy at first, was invaluable. It permitted rapid decisions on material settings and light placement.

Image courtesy Nvidia.

The best thing about Iray however, is its simplicity. It really is very easy to use and looks amazing. A rare combination. This makes it trivial turn out an amazing render with Iray. There's very little head-scratching or weird rendering artifacts or bizarre tricks required get a particular look. Instead, Iray pretty much just works.

Automatic physical accuracy has one down side: Things like turning off shadows for a given object is simply not possible with Iray. (At least, not in the traditional sense. There are ways around this.) Don't fret however, because a consequence of being simple to use and providing such rapid feedback, makes the need for these hacks greatly diminished. Instead, things just look amazing all on their own. You really don't have to cheat to make things look great with Iray.

Given how new the plugin is for Maya, Iray doesn't yet work with all of Maya's features. For example, Iray doesn't support Maya Fluid volumes yet. Meshed fluids that you can assign Iray shaders to, however, will render. Iray also won't render PaintFX or NURBS surfaces, etc. Given the complexity of Autodesk Maya, there's a lot of features they have yet to implement but even despite this, for most users I'd argue Iray is already a very usable, if not invaluable product.

Stability wise, it was pretty decent. Not perfect, but one must keep in mind I was using the beta at various stages. The latest version of the beta just prior to launch was pretty stable. The released product even more so.

Material Definition Language (MDL)
With most renderers, shaders were basically low-level C functions. This forms a tight coupling between the renderer and the shader i.e. A shader only worked with one specific renderer. With Nvidia MDL (Material Definition Language) there is a strict separation between the underlying rendering algorithms and the high-level material MDL code.

Why do you care? Basically, it means MDL materials can be used with any renderer that understands MDL and the results will be almost identical. You can create materials to be used with Iray for Autodesk 3ds max and pass them to Iray for Autodesk Maya or Iray for Robert McNeel & Associates' Rhino, or pass them to Mentalray standalone - any renderer that speaks MDL. This makes it easy to build up a library of materials you can use in all of your projects with different products. The MDL specification is freely available to third parties to implement in their own rendering products.

Reflections, refractions, soft shadows, volume scattering, both forward and back, is correctly rendered by Iray.

Iray uses MDL for everything, including lights. There are no special constructs like directional lights or area lights. Instead, you simply attach an emissive material to geometry and it's a light. You can literally model your lights. You can even animate and deform your lights because they're simply polygon objects. Of course, there's also support for Image Based Lighting and a robust built-in sun/sky system.

Iray will even correctly render color dispersion in caustics as indicated by the tiny rainbow patterns.

Making complex materials was pretty easy. Most users can simply stack together various primitive materials in the UI like Maya's Hypershade and until they get the look they want. With rapid rendering feedback, this is very easy to accomplish. Advanced users can open a text editor and write MDL directly - which is also surprisingly easy. MDL is a tiny C-inspired language. Nothing too complicated.

Image courtesy Nvidia.

With the release of Iray direct to consumers, NVIDIA also released a library of MDL materials that behave like their real-world counterparts. Some were even measured materials - which guarantees they mimic their real-world counterparts. Paul Debevec would be proud! Combine this with the accuracy and simplicity of Iray and it opens possibilities: quickly see how your design interacts with light and make rapid design decisions - which is exactly what Gensler Design did with the new NVIDIA campus building prior to breaking ground.

Final Thoughts
Iray was tons of fun! On fast hardware, it's a blast! Iray is easy to use, responsive, it scales, it's accurate, it has great materials it looks amazing. New materials are easy to make. You can use your materials with other MDL compatible products. It's competitively priced. (At the time of this writing its like $295 USD per host per year.) It's hard to find a down side.

For many users, particularly in architectural and product design, as well as freelance artists and those with hard deadlines - you really can't afford not to combine it with compatible CUDA hardware. When you do, the workflow really is that much faster than competing products. If you don't have CUDA hardware Iray will fall back to using CPU-only mode. You'll certainly take a performance hit.

NVIDIA Iray makes artists and designers significantly more productive. Go play with the 90-day free trial! It's tons of fun.

Video: Iray for Maya plug-in

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