AW: [Radiance-general] Re: Light incident direction in function files

[Peter Apian-Bennewitz]

Frank Eggenstein wrote:

>...
>
>Do you have any good idea to realize this behavior in Radiance?
>
>Best regards and a nice, hot day (today, we' ve got more than 98?F here in 
>Germany (outside, in the shade))
>
>Frank
>  
>
HOEs could be modelled using Roland Schregle's photon-map implementation 
(http://www.ise.fhg.de/radiance/ and 
http://radiance-online.org/examples/pm-pab/) if photon-map handled 
arbitrary user-defined cal files yet. Meanwhile, you could ask Roland 
about support for prism/prism2 materials, which would give an 
approximation of one HOE type (whose core advantage is of course to be 
much more flexible than prisms). Or model a diffractive structure with 
an approximative equivalent BRTF using dielectric and try to use this 
Hartmann constant (if photon-map supports it) to get the wavelength 
dependancy (ugly as sin to model HOE using diffraction). Not 
straight-forward, but rather cumbersome workarounds. Do you have a 
specific HOE to model or do you want to show the principle ?
If three color channels are not sufficient and the project is worth the 
extra work, run Radiance multiple times with different channels .
-Peter

PS: Radiance-online's mailinglist archiver doesn't handle email 
attachements well, so they won't show up in the archives.

-- 
 pab-opto, Freiburg, Germany, www.pab-opto.de