GDL light definition

[Rob]

I am trying to make light library part that could understand wattage/type of lamp/lumens definition (as we know them from lightning catalogues) by "twisting" Archicad standard parameters to particular rendering engine param's such as Archicad internal rendering engine or AV_works add-on. Does anybody know the Archicad's internal formulas used for distance_falloff and angle_falloff calculation? Are they exponential or linear functions?

[Dwight]

You will not succeed in your quest. All real luminaires have a non-uniform projection of light that is complicted by diffusion and reflection by their real diffusers and reflectors - elements that ArchiCAD's rudimentary rendering engine can only hope to approximate. And by this, I mean that when your real lamp is putting out 600 lumens, your ArchiCAD lamp is "on." and when your real lamp is putting out no lumens, your ArchiCAD lamp is "off." [joke.]

Brightness controls on most lamps are designed to define the arbitrary fall-off and limiting distances that only computer programs can image - real light rays carry on for incalculable lengths....

Archlumos, a new radiosity imager for ArchiCAD claims to be able to employ the IES profiles in calculating lamp output but I have yet to verify the accuracy of this. I think that it is a waste of time to attempt anything more than an approximation.

Besides, if it is for an illustration, you know the second thing your architectural photographer brings after his camera - his lighting - to boost ambient levels enough to make a readable film image.....so much for accuracy....

[Dwight]

And now I'm embarrassed by my incomplete answer, drafting on the inside as I am, our colleague Thomas Holm, to grasp the coveted position nine in the posting steeplechase.

It would be more accurate to say that there is no way to calculate "fall-off" accurately in ArchiCAD because it simply can't correspond to real physics, although in some lights an inner and outer sphere can be defined with a more abrupt or less abrupt decay - an arbitrary way to fake diffusion.....

Another problem with all architectural computer lighting is that in real life, a light fixture scalds the wall surrounding it, but you probably don't want this to happen in an illustration.
See attached - archicad with photoshop.

[Rob]

I know, I know Dwight...
I am pretty aware of Archicad's lighting design "stupidity" and/or "fake" renderings produced by existing add-ons. I am not going to make a breakthrough in the rocket science. I am just trying to make it a little bit more comfortable for our viz guys at our office, that's all... Anyway thank you for comments.

[Dwight]

Oh.

[Djordje]

Rob wrote:
I am trying to make light library part that could understand wattage/type of lamp/lumens definition (as we know them from lightning catalogues) by "twisting" Archicad standard parameters to particular rendering engine param's such as Archicad internal rendering engine or AV_works add-on. Does anybody know the Archicad's internal formulas used for distance_falloff and angle_falloff calculation? Are they exponential or linear functions?

The lamps that come with ArchiLumos (standard ArchiCAD ones, with additional parameters) have the parameters for this, and also can take IES profiles - which are essential if you want to do the real radiosity calculation, regardless of the software used. Maybe you should check with your reseller whether some help can be arranged?

[Rob]

It seems to be a good lead...

Thanks Djordje