Physically Based Rendering

Physically Based Rendering or PBR is a method of governing how the lighting interacts with a virtual environment. More specifically it is an umbrella term for a wide variety of shading schemes, all of which take into account not just the raytracing (or raycasting) of beams of light from every light source in the environment, but also the properties the materials in that environment would actually have.

In other words it takes into account what materials the textures on objects are supposed to represent, and checks to see how that material would affect a natural light beam striking it, modifying the light ray accordingly. In other words it combines diffuse and specular lighting into a single system, balancing different levels of both, according to the material encountered. This is done by making every surface reflective as a given, and then controlling how much reflection to create according to what the local database has to say about the material properties of the textures used, or even the material properties of whole objects.

Textures that would normally be considered lit by diffusion, become blurred reflections with a percentage of the light simply absorbed. As the material becomes more shiny, so the reflection becomes increasingly more perfect by stages, with less and less absorption taking place.

Understandably, PBR methods are much more computationally intensive than a simple raytrace or raycast lighting system, neither of which could themselves be described as particularly lightweight. However, because they are a single system that mimics the effects of both a diffuse and specular lighting system in one, more simple system, the effect is you are practically halving the amount of work your lighting system has to do to create realistic results, and those results certainly speak for themselves in the sheer levels of realism created.

For interactive virtual environments, PBR is still possible despite the processor overhead, so long as you are not assessing the material each polygon face is showing in real-time. Whilst real-time assessing of how a user has just reskinned an object mid-session by adding a wooden texture manually where a metal one was before, is not going to be possible with current PBR methods, a pre-rendered environment is certainly much more workable.

See Also: Raytracing, Raycasting, Ambient Occlusion, Indirect Light, Specular Coefficient, Caustic Lighting, Level of Detail, Progressive Radiosity, Luster

Below, we offer a selection of links from our resource databases which may match this term.

PBR Physically Based Rendering

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Volumetric Rendering in Realtime
A brief but thorough multi-part article from Gamasutra, on creating volumetric rendering in real-time, for use in fog, fluid, and other effects, which correctly affect light at any point through them.

AR Development > FLARToolKit
FLARToolKit stands for FLash-based Augmented Reality Toolkit, and is a port of the Java-based port of ARToolkit, NyARToolKit. The toolkit is compatible with Flash version 10, using Action Script 3, where it executes natively. Thus, unlike most AR visual toolkits, it has a limited capability when real-time rendering is maintained.

Real-Time Rendering, Third Edition

A required reading book on real-time scene rendering that has been around for years, this book serves as a holistic, platform-independent guide for creating high frame rate renders that are as realistic as possible for the hardware available ? and teaches you where the bottlenecks are in the process so that you learn how to gauge new hardware from spec and understand how it will directly impact performance.

Virtual Pain Relief: Virtual limb could provide relief from phantom limb pain
Reproduced with permission of The Wellcome Trust, this article takes a look in depth at the use of VR based limbs, to trick the brain into thinking the limb is still physically there - and make the pain vanish.

3DEE is a social worlds system based on the ActiveWorlds codebase. Like all systems based on this code, it looks and feels a bit dated, although this one has its own unique wrinkles to help take care of that. Based in Amsterdam, 3DEE?s primary language is Dutch, and the universe?s eight entrance worlds are loosely based around that theme.

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