[Radiance-general] Curved mirror surfaces

[Lars O. Grobe]

Hi Jill!

What is the modifier used to model the mirror surface? If Giovanni's
assumption is correct and your surfaces get a plastic modifier (probably
with high specular reflection), you cannot expect accurate "sharp"
shadows/highlights on diffuse reflective surfaces (such as a ceiling) as
all the light transport is handled by the ambient calculation. You would
need a mirror modifier applied to your surface. Unfortunately, with a
meshed curved surface, you would end up with a practically infinite
number of such mirrors, thus with an infinite number of secondary light
sources. There is some define in the code setting the maximum number of
secondary light sources, and one could set it higher (this has been used
for reflector modeling), but don't expect this to be efficient with an
architectural model.

I quote this from time to time (Rendering with Radiance, p. 580, chapter
13 "Secondary light sources"):

[...] "Other cases involving curved, specular reflectors pose similar
difficulties for mkillum, and the only long-term solution seams to be
the creation of a forward raytracing module for computing these kinds of
illums." [...]

What are you trying to model? Specular, curved blinds? Some kind of a
collector?

Cheers, Lars.

> Hello,
> 
> Does anyone have experience with mirror surfaces and especially curved
> mirror surfaces? I am not having luck getting sunlight to bounce off of
> them the way they should. Are there any tricks? I am using Ecotect and
> exporting to Radiance.
> 
> Thank you!
> 
> Jill Dalglish

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