[Radiance-general] gensky -u not uniform?

[John Mardaljevic]

PS.  Jan reminded me (off list) that, of course, if you *only* want a uniform luminance hemisphere, then there is no need to use gensky.  However, should you want an *exact* representation of any of the CIE types (i.e. without any blending of the luminance at the horizon), then the suggested fix will work.

By the way, for quantitative work, say, simulating illuminance values using CIE skies created by gensky, this luminance blending at the horizon will almost certainly *not* have any significant effect for anything but weird scenarios.  Thought I'd better mention that :-)

Back in 2002, I was setting up a `weird scenario': mapping the CIE clear sky pattern onto a hemisphere of finite size to predict the effect of parallax in sky simulator domes.  Since some of the sensor points were nudging right up against the (finite extent) horizon, the effect of the blending was noticeable.  That (rather arcane) study is described in a 2004 paper:

http://journals.sagepub.com/doi/abs/10.1191/1365782802li055oa

Cheers
John