[Radiance-general] Trans Oddities Part Deux

[Rob Guglielmetti]

alex summerfield wrote:
> OK Rob,
> 
> I mean if you generate a CIE overcast sky with horizontal diffuse
> illuminance of 10,000 lux <snip>
> 
> Anyway check that this test is running OK with the diffuser that is
> 'working' - then move onto the problem diffuser.

Oh, now I get it.  Thanks for explaining that to me.  I will try that. 
I'm swamped with other things at the moment, so my investigation into 
this has stalled, but I will try your technique soon enough.

> If it doesn't show the proportional relationship then perhaps some of your
> settings at these low lighting levels mean that absolute rounding may be
> having an undue effect. At low light levels small absolute errors will
> produce large percentage errors in the quantitative results.

That was my fear.

> As you may be relying on a relatively few measurement points in very low
> light levels - i reckon it would be worth doing some small renderings so you
> can 'see' what is going on - for instance observing the distance between the
> ambient calculation points causing light leakage problems (that appear as
> splotches in images) or detecting modelling errors that are not significant
> at the higher illuminance levels.

Good point.  They just take forever with all the bouncing and all.  Byt 
maybe it's warranted.

> The renderings could be used like an overture calculation - ie reuse the
> ambient file to recalculate your illuminance values and compare with
> previous results. Again there should be consistency in the results.

Good point (again), though I thought that rtrace didn't really benefit 
from an overture calculation.  Perhaps that's YAM (yet another 
misunderstanding).  Hmmm....

> hope this helps

Yeah, I think it does, thanks!  I appreciate your replies.

----

      Rob Guglielmetti

e. rpg@rumblestrip.org
w. www.rumblestrip.org