Homepage:
http://radsite.lbl.gov/radiance/
The Radiance Synthetic Imaging System has been around for
approximately 2 decades at the time this document was written.
Therefore, there is an extensive amount of information in the public
domain pertaining to it. There is also a book, Rendering with Radiance:
The Art and Science of Lighting Visualization, written by Greg Ward
Larson and Rob A. Shakespeare that describes the previous release of
the system. The book can be purchased or viewed freely at http://radsite.lbl.gov/radiance/book/index.html.
That being said, this document aims to guide you to various resources
pertaining to Radiance and to give a first hand account of use of the
system by a user who has no prior experience using public domain or
proprietary renderers.
"Radiance is a suite of programs for the analysis and visualization of lighting in design.
Input files specify the scene geometry, materials, luminaires,time, date and sky conditions (for daylight calculations). Calculated values include spectral radiance (ie. luminance + color), irradiance (illuminance + color) and glare indices. Simulation results may be displayed as color images, numerical values and contour plots.
The primary advantage of Radiance over simpler lighting calculation and rendering tools is that there are no limitations on the geometry or the materials that may be simulated. Radiance is used by architects and engineers to predict illumination, visual quality and appearance of innovative design spaces, and by researchers to evaluate new lighting and daylighting technologies."
- Short Description of Radiance from (http://radsite.lbl.gov/radiance/framew.html), who could put it better.
If you would like to read more follow the link to the Full Detail
Description.
As mentioned above, Radiance is a collection of programs. Each of
the programs fit into a complex architecture, which make Radiance a
complete imaging system rather than just a renderer. At the center of
the architecture are rendering programs, which take a scene description
and produce a visualization. One such program is rpict, which takes a
scene description and produces a high-quality, lighting-accurate
rendered image. Rendering a 2-D visualization from a 3-D scene
description is done via RAY TRACING method, where the ray is traces
backwards from image plane to source. In order to meet the goals of
providing a system for highly accurate light calculations, the render
supports various light-surface interaction models and illumination
models. The system also simulates lighting from the sun given a date
and time. This allows advanced analysis of architectural design.
Other key programs in the system are centered around modeling or converting models, and producing octrees (oconv). There are also many programs that tie the entire system together and the user does not directly interact with.
Radiance was originally developed for Unix-based systems. Since its release into the open source community, support has increased for other OSes. One major target user group for the software is architects who want to render their models with realistic lighting. Due to the popularity of modeling applications on Windows and Mac OS, the ability to use Radiance is of great convenience.
Radiance for Mac OS X is fairly easy to setup. Precompiled binaries are available on the Radiance website, which will speed the installation process. If you use the precompiled binaries, you will still need to download and unpack the distribution file, which contains a variety of useful items (i.e. sources, libraries, examples, man pages...). The easiest way to set up the system is to follow the readme file contained in the distribution.
X11 m ust also be installed on the machine to use some of the basic components of Radiance. Unfortunately, X11 is not installed by default on machines that were bought with OS X preinstalled. If this is the case for you and you have not already installed it, then X11 can be installed easily from the software disk bundled with the machine.
Desktop Radiance is a
software package for Windows, which bundles Radiance and AutoCAD for
the purpose of quickly creating realistic lighting models. I have not
investigated this package. Also you may want to check out ADELINE.
Scene descriptions represent a 3-D environment and consist primarily
of primitive surfaces and modifiers. Modifiers consist of
materials, mixtures, textures, and patterns; these can be applied to
surfaces or other modifiers. Surface primitives consist of several
regular geometric shapes, source (a solid angle, which can be used to
describe a distant light source), instance (which can be used to make
multiple instances of a compound surface), and mesh. Commands can also
be included in scene description, which allow generation of parts of
the scene by way of external program. Generators are the general name
for this type of program and several are included with the distribution
(e.g. genbox - generates a box made of polygons; genworm - generates a
worm structure). External models of various file format can also be
imported and converted to primitive surfaces using some of the programs
included in the package. For instance, obj2rad can be used to create a
radiance scene description from a .OBJ file.
Any of the surface primitives can be used to model a light source or
various types of material, given that the material modifier is set
appropriately.
Texture and patterns can be applied to objects using modifiers.
These images were made by following the Radiance tutorial all the way to the last step. For these images interreflection was used, this looked much better than when rendered with the mkillum method as suggested. The benefit of using interreflection is increase in detail, this is especially pertinent to shadows and highlights, but there is an increase in rendering time.
This is a variation of the Radiance tutorial scene where the ceiling light is removed and the only illumination. One of the features provided by radiance is the ability to simulate sunlight by giving date, time, longitude, and latitude. This is a variance of the scene at 4 different times. Note: the conversion from the default format .pic to a web safe image format (.bmp) changed the overall intensity levels of the images.
My Scene B is the same structure as the tutorial scene except that the window and sunlighting is removed. The bulb light in the room is replaced with a light that only directly illuminates the ceiling. In the first rendering the same gray plastic material from the tutorial is used for the ceiling. On the second rendering, a mirror material is used for the ceiling. The floor here is a dielectric material exhibiting equal reflectance over all colors.
My Scene C is a box with all mirror walls. There is an Illum type light source in the middle of the box, which illuminates the scene but is invisible when viewed directly. There are 3 chrome pipes running through the room.
To summarize, the Radiance Synthetic Imaging System has grown well with age. Almost 2 decades after its creation and the system is still useful and powerful. The system has a command line interface, which is simple but does not provide the amount of environmental knowledge, as would a graphical interface. This gives the system a steeper learning curve, because the user has to learn what commands/functions/programs are available. Fortunately, there is a great deal of public domain documentation for the system, which makes getting started an easy task. Included in the distribution are several programs that ease the process of setting up a scene and rendering it. For example, there is a program (rad) included with the distribution which acts like Make, and it makes rendering a one call process. Another program is rvu, which allows the user to interactively move the camera around the scene and save viewpoints. Scene file format was pretty intuitive, and with the help of the Radiance reference manual it was easy to set geometry and material properties. Lighting setup was just as intuitive as setting scene geometry and material properties; well, that is because light sources are just surfaces with the material set to a light emitting type.
One issue I had with the system was setting the camera view. Changing this within rvu was difficult because it required entering text commands which describe the camera movement relative to the current position. However, once a good setup was found, it could easily be saved for used later. This was very helpful.
One suggestion to anyone who wants to start using this renderer is that you should begin by completing the Radiance Tutorial and also read through the Radiance Reference Manual