At a basic level, the natural world can be modelled as the interplay of energy and matter (for example in form of a 3D configurator). This interaction can in turn be observed by the viewer through the visible appearance of the world.

In this model of the natural world, the appearance of an object is a consequence of the matter it constitutes. In other words, appearance is an intrinsic property of an object. However, in order to facilitate the assignment of intuitive categories of the natural world to a simulated world, a formal model can separate the appearance of an object from the object itself. Appearance is then an extrinsic category between the viewer and the interaction of energy and matter. The definition of appearance as an extrinsic property also has a very useful side effect: the separation of the appearance of an object and its geometric structure provides an experimental freedom that is fundamental to the role of rendering in design and visualization tasks.

iRay conceptual modeling

Iray maps the conceptual categories of the natural world model – energy, matter, appearance and observer – to categories that are suitable for describing a simulated world: Light, geometry, material and camera.

There are three important points to bear in mind when assigning these categories:

  • Objects are abstracted to their geometric form.
  • The interaction of light with the geometric shape of an object is defined by a material that determines its appearance. The interactions of light and objects are captured in analogy to a conventional photo camera.
  • Lights, geometries, materials and cameras in a simulated world and their spatial relationships form a scene. In iRay the scene is the simulated world to render.

Create a record of the world.

The virtual camera specified in a scene defines attributes analogous to those that characterize a real mechanical camera, e.g. viewing direction and focal length. But unlike a real camera, a virtual camera cannot record a scene. This task is performed by the renderer.

The strategies for creating a recording of a rendering can vary depending on the renderer. In raytracing, for example, lines drawn from the camera’s “eye position” into the scene determine the color values of the corresponding position in the resulting data set. In other words, the camera determines the geometry of the relationship and the renderer controls how the color values are calculated. The control of the renderer depends strongly on how the renderer is implemented in the software. The development of an intuition for controlling the renderer requires an understanding of the rendering process itself.

The rendering process.

In the following we describe the inputs, processes and outputs that are assigned to the phases of the rendering process:

  • Input – The scene that contains the description of the world and a position and direction from which to view it. The more extensive and detailed the description, the more realistic the interaction with surfaces and volumes can be modeled.
  • Processes – The renderer that processes the scene description. The algorithms implemented by the renderer determine its ability to record and represent the behavior of light and its interaction with objects.
  • Output – The output of the rendering process, which is an image – the recording of what the camera has “seen”. The quality of the image is determined by the complexity of the file storage format and the capabilities of the output device used to display the image.

Material Concepts.

MDL: The standard for materials.

Materials in iRay for 3ds Max are based on MDL (Material Definition Language), which consist of building blocks that can be flexibly combined. MDL is an open standard for describing materials and the interaction of light on their surface and volume. Iray materials simulate the entire illumination equation and lead to simulation accuracy by using measurement data in their materials.

iRay introduces a variety of materials that form starting points that can be adjusted to represent almost any material with accuracy. Materials can be shared with other MDL-enabled applications, so all designers, developers, and others working on a project can work with a single set of materials.

Realistic structure.

Iray+ material layers follow the real material formation structure so that the way you see them in iRay for 3ds Max follows how they would be made or found in nature. A lacquered wood, for example, follows the structure:

  • Decal: Vinyl Sticker
  • Surface 1: Scratches the alpha channel
  • Surface 2: clear lacquer lacquering
  • Coating: varnishing with diffuse colour
  • Base: Pine Wood with Bump Map
  • Geometry: Forest Geometry

They are created in a top-down structure, with the core geometry at the lower end of the layer order and, if necessary, additional layers built on top of it. Multiple layers of each type can be added in any order, enabling highly complex surfaces such as multi-layer paint stripping and rust, chips and scratches.

Developed with the aim of collaboration.

The practical material approach enables efficient reuse and distribution of the individual components to different materials. For example, you can take the paint, varnish and decal from the pine base and add them to a plaster or concrete base. Very quickly you have created a new material from these building blocks, without the tedious work of starting all over again.

The large material library already included in iRay for 3ds Max allows you to create even the most unique materials extremely quickly. The open nature of MDL allows for exchange between communities and between applications, eliminating much of the repetitive work normally required.

Lighting concepts.

The light in an iRay scene can come from three sources: global lighting from the environment, emitting materials, or artificial light within the scene. A scene can be illuminated entirely from one of these sources or from a combination of the three. These three large categories can be further subdivided into more specific light sources or types. Ambient lighting can come either directly from an IBL (image-based lighting) or from a procedural solar and sky simulation environment called PhysicalSky. The artificial lights are available in different versions, some of which are controlled by the usual 3ds Max light types and others that are unique to the iRay plugin.

The lighting systems in iRay for 3ds Max are all physically correct, so when you add real-world data to a model or simulation, you get precise lighting. This is perfect for studying light in simulation and creating more realistic animations. The PhysicalSky environment is ideal for daylight studies and provides accurate luminances in any model.

In addition to adding new iRay luminaires to powerfully control the appearance of your scenes, we support many of the existing 3ds Max luminaires, so your existing models will work as expected without having to replace the existing lighting.

Illumination of the surroundings.

Iray uses the concept of environments to describe the world around the scene. These serve to give the image the visible background (with missing backplate) and also to illuminate the scene. The IBL environment can be specified either as a sphere or hemisphere and additional parameters that allow you to control the size of the dome and various baseplate effects.

Iray also offers a powerful process environment called PhysicalSky. This creates a physically realistic, highly dynamic light dome around a scene. You can control many aspects of this dome, including overall intensity, sun position and sky appearance (sun position can be adjusted either directly with a height-azimuth coordinate system or via the extensive date/time/location panel). Since this is physically accurate, you will see realistic halo effects around the sun disk, atmospheric turbidity, sky color, etc., and you will be able to see the effects of the sun’s rays in the sky.

Artificial lighting.

Iray has several types of artificial light that can be used to partially or completely illuminate a scene. As mentioned earlier, some of these light types are used in conjunction with the standard 3ds Max light types to integrate seamlessly into your existing workflow, while other light types are unique to the iRay plugin and are controlled separately.

3ds Max Lights.

The following light types are used when switching from the standard 3ds Max light types. In the iRay plugin, no special controls are added for them, but the most suitable type is automatically selected for the best conversion.

Distant Lights.

High beams function as point light that is placed infinitely far away from the scene. The lighting is parallel and uniform – i.e. each point in the scene “sees” the light in the same direction and with the same intensity. Essentially, it imitates simple sunlight.

Point lights.

Point Lights provide even light distribution from a single point within the scene. The illumination at each point of the scene depends on the direction to the light position from the point of view of that point and is also proportional to the inverted square of the distance between that point and the light position. The light source is not visible in the scene.

Spot Lights.

Spot lights are similar to point lights, but the light distribution is not spherically uniform. Instead, it is directed into a “cone” to mimic the look of a real spotlight. The light source is not visible in the scene.

Photometric Lights.

Similar to point and spot lights, but not uniform or simply conical, this light type reads an external IES file that describes a more complex light distribution. This distribution can be aligned like the Spot Light, but the actual shape of the distribution is determined by the IES file. The light source is not visible in the scene.

Area Lights.

Area Lights are unique to the iRay plug-in and therefore have their own controls and user interfaces.

Area Lights define simple geometries (rectangles, discs, spheres and cylinders) that emit light. In contrast to the other types of artificial light, these are visible in the scene by default, so they are well suited for modeling simple light bulbs, light bands and the like. They can also be made invisible to the camera, like all other types of light. Each type of Area Light has parameters that allow you to set the position, size. Shape and orientation of the light can be controlled. By default, the Area Lights provide a uniform background illumination, but it is also possible to attach an IES file as with the Photometric Lights. In this case, each point on the surface of the area light with this profile acts as a point source, the overall illumination is given by an integration over the surface.

Rendering concepts.

Iray offers various renderers that are tailored to the execution of specific rendering tasks. Iray+ is a production renderer with full global lighting support. Iray+ Interactive allows you to quickly interact and change your scene. This “Unified Rendering Model” means that all renderers share a common representation of your scene and materials in 3ds Max. This ensures consistency of appearance regardless of which renderer you use. If you use other iRay-enabled software in your workflow, this consistency extends across the entire workflow.

Scalability concepts.

Designed to take full advantage of your GPUs, Iray offers massive performance improvements in rendering speed when you add additional hardware. This makes it an incredibly efficient choice for using distributed rendering in your workflow. Cluster or render farms are supported by default with the 3ds Max batch rendering tool or other add-ons such as the Backburner. Cloud rendering support is standard and extremely easy to set up.

We hope we have been able to give you a deeper insight into the subject. If you have any suggestions or questions, please feel free to contact our experts in our forum.

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