[Radiance-general] Modelling 'LitraCon' Light-transmitting Concrete

[Gregory J. Ward]

Hi Terry,

This is no help, really, but I would suggest transdata with some  
appropriate angular measurements.  Are there any?  Plain  
transmittance isn't enough to capture the distribution of light,  
which I wouldn't expect to be diffuse.  In the absence of any  
measurements, I suppose you have to assume it's close to diffuse and  
use their value of 3% of 88% for 4% fiber volume density.  So, that  
works out to a formula of:

	transmittance = 0.66 * fiber_density

You can then plug this into a trans primitive:

conc_pattern trans litracon_TM
0
0
7 {refl+trans} {refl+trans} {refl+trans} 0 0 {trans} 0

(Replacing the things in curly braces with appropriate values.)  I  
don't know what the reflectance is -- between 10% and 30% I suppose  
but they don't say.  As for the concrete pattern, you can use a noise  
function if you like, but I doubt it would look very convincing up  
close:

void brightfunc conc_pattern
2 '1+0.2*fnoise3({sca}*Px,{sca}*Py,{sca}*Pz)' .
0
0

You'll have to pick the scale to suit your coordinates, and you may  
want to use different ones for Px, Py, and Pz to get a grain  
appearance, for example.

-Greg


P.S.  I love the spotlight selector thing on their website -- very hip.

> From: "Terrance McMinn" <T.McMinn at curtin.edu.au>
> Date: October 18, 2006 7:57:40 PM PDT
>
> I have a student who is currently designing a museum for his
> dissertation. Can anyone offer advice in modelling this
> Light-transmitting Concrete
> (http://www.litracon.hu/building-blocks.php)?
>
> For those who have never heard of this material before, it is  
> basically
> concrete with embedded optical fibres.
> Initial thoughts are to model as 'trans' material modified with a  
> dirty
> function for the opaque areas, though there is a definite suggestion
> that the optic fibres be arranged in rows or columns within the block.
>
> Regards
>
> Terry Mc Minn
> Faculty of Built Environment, Art and Design
> Curtin University of Technology
> GPO Box U 1987 Perth 6845 Western Australia
> Email: T.Mcminn at curtin.edu.au
> CRICOS Provider Code: 00301J