I'm pretty new to Radiance, so please bear with me 
I have a commercial forward ray tracing program that I use to model complex window glazings. I can output the transmitted flux vs outgoing direction for light incident at different angles.
How would I create a surface in Radiance which would behave in the same way as observed using the forward ray tracer. BRTDfunc? Can I specify arbitrary output distributions for a comprehensive sampling of all incoming directions? Is there a "BRTDdata" surface type?
Any ideas? Other things I should be aware of?
Thanks
Frank
路路路
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Hi Frank,
The transdata function will allow you to specify an arbitrary BRDF on a surface, but it won't necessarily do what you want unless you use the photon-mapping add-on by Roland Schregle. I plan to work on a module that will create "window sources" similar to mkillum given measured BTDF data, but this won't be ready for some months.
I realize this isn't much help, but I'm afraid the options are currently somewhat limited.
-Greg
路路路
From: "FrankBob Holly" <[email protected]>
Date: April 20, 2007 11:14:38 AM PDT
I'm pretty new to Radiance, so please bear with me
I have a commercial forward ray tracing program that I use to model complex window glazings. I can output the transmitted flux vs outgoing direction for light incident at different angles.
How would I create a surface in Radiance which would behave in the same way as observed using the forward ray tracer. BRTDfunc? Can I specify arbitrary output distributions for a comprehensive sampling of all incoming directions? Is there a "BRTDdata" surface type?
Any ideas? Other things I should be aware of?
Thanks
Frank
Hi Greg, Thanks for the reply.
I found the Photon Map Manual here http://www.cb-d.de/rz/pmap.pdf and it says on page 5 that transdata is not a supported type of material "due to the high sampling overhead in conjunction with the photon map. A wavelet representation is being developed for these. (But don't hold your breath...)"
Is there any other possible solution?
Frank
路路路
From: "Gregory J. Ward" <[email protected]>
Reply-To: Radiance general discussion <[email protected]>
To: Radiance general discussion <[email protected]>
Subject: Re: [Radiance-general] Specifying surface properties from BTDF data
Date: Fri, 20 Apr 2007 14:57:53 -0700
Hi Frank,
The transdata function will allow you to specify an arbitrary BRDF on a surface, but it won't necessarily do what you want unless you use the photon-mapping add-on by Roland Schregle. I plan to work on a module that will create "window sources" similar to mkillum given measured BTDF data, but this won't be ready for some months.
I realize this isn't much help, but I'm afraid the options are currently somewhat limited.
-Greg
From: "FrankBob Holly" <[email protected]>
Date: April 20, 2007 11:14:38 AM PDT
I'm pretty new to Radiance, so please bear with me
I have a commercial forward ray tracing program that I use to model complex window glazings. I can output the transmitted flux vs outgoing direction for light incident at different angles.
How would I create a surface in Radiance which would behave in the same way as observed using the forward ray tracer. BRTDfunc? Can I specify arbitrary output distributions for a comprehensive sampling of all incoming directions? Is there a "BRTDdata" surface type?
Any ideas? Other things I should be aware of?
Thanks
Frank
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Hi Frank,
I'm out of ideas for other workarounds. You may just have to wait until I get this new facility working. I wouldn't be developing it if there was something else that could work. Since they recently added BRTF/BRDF data exporting to LBNL's Window 3, they're hiring me to support it in Radiance.
Best not to count on this before Fall, though I'd like to get it done sooner than that -- Summer if I can manage it.
-Greg
路路路
From: "Frank Holly" <[email protected]>
Date: April 25, 2007 6:05:07 AM PDT
Hi Greg, Thanks for the reply.
I found the Photon Map Manual here http://www.cb-d.de/rz/pmap.pdf and it says on page 5 that transdata is not a supported type of material "due to the high sampling overhead in conjunction with the photon map. A wavelet representation is being developed for these. (But don't hold your breath...)"
Is there any other possible solution?
Frank
