To simulate the perfomance of things like light pipes, you need to use a tool with forward raytracing capabilities, radiance in its classic form is a backward raytracer:
* forward raytracing - trace rays from sources in scene to eyepoint
* backward raytracing - trace rays from eyepoint back into scene
One way to do forward raytracing is "photon mapping." Roland Schregle has written an extension to radiance that performs photon mapping:
* http://www.radiance-online.org/ see "examples & extensions" in the
Since this is an extension to the core radiance engine, this will require moving beyond Desktop Radiance.
Note there are two prism material types in Radiance: prism1 and prism2. These would probably be useful for defining the properties of the prismatic glazing, the trick is acquiring perfomance data for the physical material(s) and correctly modeling the behavior with these radiance material types. I have not really used these material types before. However there should be others in the group who can provide feedback to you.
It is also possble the depending on how you breakdown your problem that there are simpler ways to do what you want. For example what are the key issues of what you are trying to simulate and evaluate:
* properties of light pipe performance - then this probably requires
the use of photon mapping
* properties of prismatic glazing as enhancers of light distribution
- can this be seperated out from the light pipe and evaluated
using more classic techniques in standard radiance, in other words
can you make some estimates for light output from the side
apertures of the light pipe and thus remove the actual simulation
of the light pipe behavior?
I expect you wil get other input, which I will look forward to reading myself.
-Jack de Valpine
PS: I have cross posted to radiance-general, to give the discussion wider input.
Anthony J. Farrell wrote:
I wish to analyse the light distribution to an office room supplied from a
light pipe fitted with side apertures.
The apertures will contain prismatic glazing or a blind reflector.
I have drawn the light pipe using desktop radiance, and made the surface 97%
spec ref. as from typical light pipe manufacturers data.
I wish to include prismatic glazing or other novel glazing types such as
blind reflectors to enhance the light distribution from the side aperture.
Can anyone give me some insight as to how I may do this, since the glazing
database that comes with desktop radiance only contains common glass types,
and not prismatic or such like - perhaps one of you know of a patch for
desktop radiance that provides several different prismatic glazing types, or
of code for Radiance that includes for it.
Thanks, and best regards,
Dublin Institute of Technology, Ireland.
# John E. de Valpine
# visarc incorporated
# channeling technology for superior design and construction