[Radiance-general] Daylight simulation for Multi-Layer ETFE Pillows

[Lars O. Grobe]

Hi Mostapha,

it depends on what results you are looking for.

If you need a useful model of the transmission through your fenestration, you may consider using the glass modifier. There is an error in this, as the refractive index of ETFE is lower (should be 1.4) than that of glass, however, for a clear, thin ETFE film, this may be rather ok for near-normal angles.

In some of the images, the ETFE did not seam to be clear. Probably it hat be printed, or some surface treatment had been applied to roughen it. In this case, you need to model the surface as it is, which has little to do with the pure material properties of ETFE. Probably you need some data on the transmission and reflection, provided by the manufacturer or by your own measurements. That would allow you to approximate a trans / transfunc material to your sample.

If you want to model something like patterns, where parts of the surface are printed and others are not, you can use mixfunc and mix the surface material with a clear ETFE material.

The multiple internal reflections would be accounted for when directly looking at the pillow. Bright spots by such reflections e.g. on a ceiling or wall would not appear. That would require secondary light sources (not very useful for the complex geometry), the pmap, or maybe a precalculated BSDF of one pillow.

Cheers, Lars.