[Radiance-general] physically-based landscapes

[Rob Guglielmetti]

On Saturday, May 31, 2003, at 05:45 AM, Carsten Bauer wrote:

> Hi Rob,
>
> is there snow on the mountain top? Can you go skiing over there?

Yes and no.  There is snow on the peak, but I cannot go skiing over 
there, because if you strapped a pair of skis to my feet and pushed me 
down a snow covered hill, I'd turn into a dangerous projectile for 
about five seconds before crashing.  It's definitely not what I'd call 
skiing.  =8-)

> Excluding objects form the ambient calculation is done by setting the 
> -ae
> parameter to the objects material name (-ae mat_name or -aE
> file_with_matnames). So excluding the mountains is no problem, the 
> drawback
> is, that Radiance determines the resolution of its ambient cache (-ar
> setting) dependent on the scene bounding cube. So a HUUUGE bounding 
> cube
> results in values spaced so far apart that probably only one falls 
> into your
> room. (Unless you set up -ar extremely high, if everything outside is
> excluded, this might even work ...)

See my response to Greg about this one...

> But why not tread an intermediate path: set up a 3D landscape model 
> and render
> some pictures with it from your viewing point.  They contain the exact
> radiance values, so in a second step you can map them with colorpict 
> to a
> plane made of  glow with fourth param set to zero, and put this plane 
> 100 or
> 200 m apart from your scene. This will keep the blowing up of the scene
> reasonable and still deliver correct results. Do some checking if the
> settings are right, i.e compare the landsscape rendering with your fake
> landscape rendering, one never knows ...)

OK, so this is basically using Radiance to create a "lightmap", instead 
of using HDR, yes?  I assume I could further increase the accuracy by 
using your method described here, but then also using mkillum to create 
illum sources out of the window panes?

Am I making any sense at all??!!

Rob Guglielmetti
rpg@rumblestrip.org
www.rumblestrip.org