Autodesk Expands Photorealistic Rendering Options9 Dec, 2015 By: Randall S. Newton
After several years of acquisition and development, two ray-tracing engines reach the market — one in standalone format, and the other as part of existing Autodesk software products.
For years, a vibrant network of third-party solutions (including V-Ray from Chaos Group, AccuRender from Robert McNeel & Associates, and many others) has been providing alternatives to and augmenting the existing rendering and visualization technology inside Autodesk applications such as AutoCAD, Inventor, and Revit. Even Autodesk’s two best-known animation and visualization products, 3ds Max and Maya, work with a variety of third-party rendering products.
In recent years, however, Autodesk has aggressively built up its in-house rendering expertise through acquisition and research. The results of those efforts are now starting to hit the market, in the form of two ray-tracing engines — one that’s embedded within the design workflow, and the other for standalone rendering projects.
An Introduction to Ray Tracing
The most popular technology for turning CAD models into polished, photorealistic visual images is ray tracing, which mimics the real-world effects of light bouncing off objects. Ray tracing makes light a calculated data type instead of a manual input, allowing ray-tracing solutions to run much faster than other approaches to photorealistic rendering. Each digital ray of light is analyzed repeatedly as it moves and bounces through the model; the longer a ray tracing engine works on a model, the more sophisticated and realistic the image becomes.
Ray tracing simulates the results as if the objects in a model were physical objects. It relies on previously defined physical definitions for all objects in the model; contemporary design software, for the most part, supplies this information as the design is created. (Occasionally, a rendering expert will edit assets after the fact.)
The data that define each material in a model are organized as assets: properties that control the characteristics or behavior of the object. There are four primary asset classes used in Autodesk products, but not all products have all four classes. Here are the classes, their definitions, and examples of the products using them:
- Graphics: Properties that control how the material looks in non-rendered views (Revit);
- Appearance: Properties that control how the material looks in rendered views, realistic views, and ray-traced views (AutoCAD, Inventor, Revit);
- Physical: Properties used for structural analysis (Inventor, Revit);
- Thermal: Properties used for energy analysis (Revit).
Materials in a model can have a maximum of one asset of each type. For example, an Inventor material can have both an Appearance asset and a Physical asset, but not two of either class. An AutoCAD material, however, can have only one Appearance asset; it does not have any other classes of assets.
Autodesk Raytracer: The Integrated Option
Currently, Autodesk is updating many of its products with a new ray-tracing engine it developed in-house. Autodesk Raytracer is included in the current versions of AutoCAD, Navisworks, Revit, and Showcase. It is also available as a free Autodesk Labs Technology Preview for 3ds Max.
Third-party ray-tracing software generally appeals to visualization specialists with a broad set of tools to manipulate the rendering. Autodesk Raytracer, in contrast, is a generalist tool; it provides a simplified feature set. The image below shows the dialog box that appears when Autodesk Raytracer is in use within Revit Architecture. (NVIDIA mental ray software is still included in Revit, and remains an option when more complex features — such as Daylight Portal — are desired.)
The Autodesk Raytracer rendering engine is now included in all versions of Revit 2016. Image courtesy of Autodesk.
Renders can be completed locally or sent to a cloud service. The technology uses only central processing units (CPUs), not graphics processing units (GPUs), making it cheaper to run as a cloud option where time on GPU clusters is more expensive.
Autodesk VRED: The Standalone Tool
Autodesk’s recent visualization push doesn’t end with Raytracer. In 2013 Autodesk acquired PI-VR, a privately held German software developer with a sophisticated real-time rendering engine called VRED. It is a high-end tool, intended for photorealistic design visualization in product development. Autodesk places a heavy emphasis on VRED’s support for the design tools in Autodesk Alias industrial design software, and its suitability for quick turnaround of visual prototypes.
Autodesk VRED is a sophisticated photorealistic tool for product development. Image courtesy of Autodesk.
VRED has two modes of user interaction. In Simple mode, it is a matter of letting the software use default settings. For those ready to dig in deeper, the Complex mode offers camera control, surface analysis, comprehensive material libraries, real-time ray tracing, animation, and stereo display; the Professional version even supports the Oculus Rift virtual reality headset.
VRED is complex enough to allow selective resolution, where certain parts of the model are rendered at a higher resolution as a special effect. This is handy for creating advertisements that draw the viewer’s eye to a particular part of the image. Unlike most renderers, which work with the materials data supplied from the CAD program (if available), VRED requires that the user adds material designations, in addition to setting the lighting and scene conditions.
The addition of the VRED team brought new energy and high-end technology to Autodesk’s visualization offerings, and has contributed to the development of Autodesk Raytracer, which is now packaged with its flagship products. As with every technology, however, there are trade-offs. The addition of Raytracer makes rendering part of the design workflow, but in a limited fashion; it lacks the bells and whistles of a dedicated product. In contrast, VRED is a dedicated, full-featured visualization engine, but it is not integrated into the design workflow. If something changes in the product model, you have to start again with the VRED visualization.
In addition to these new Autodesk-provided options, a wide array of competitors continue to offer visualization solutions for both architecture and product design, including plug-in support for Autodesk’s flagship products. As CPU cores become denser and faster, and as cloud and GPU support become more common, the next couple of years should be a time of rapid growth in the use of photorealistic rendering at all stages of the design process.