This went to Greg, but should have gone to the list. More thoughts on this topic...
···
-------- Original Message --------
Subject: Re: physically-based landscapes
Date: Tue, 03 Jun 2003 16:58:47 -0400
From: Rob Guglielmetti <[email protected]>
Reply-To: [email protected]
To: Greg Ward <[email protected]>
References: <[email protected]>
Greg Ward wrote:
>> From: Rob Guglielmetti <[email protected]>
>> ... Carsten says that the -ar
>> is based on the scene bounding cube, so even if I exclude the exterior
>> values I need to crank it up, yes?
>
> Yes, though you could set -ar 0 and you might get around this problem.
> The disadvantage is that the calculation can go a bit nuts in the little
> corners, but it's only a problem on high-resolution renderings. Rtrace
> shouldn't be much affected.
Ahhh, but I *always* do renderings now, so that that ambient cache is
well populated! =8-) No matter, I'm much more interested in making
option two work...
>> The illum's luminous distribution function is the result of applying
>> the lightmap to the window pane, just the same as if I were to use
>> gensky? The colorpict is purely for the view out, it does not
>> contribute to the illuminance of the interior space?
>
> No, it's the same as if you used mkillum. The only difference is that
> rpict -vta -vh 180 -vv 180 computes the window's light distribution from
> a single viewpoint, where mkillum would average it over the entire
> window. If your window is small relative to the closest geometry, the
> difference is vanishingly small.
Well, the window mullions are pretty deep, but other than that, no.
Now, your method utilizes a hemispherical fisheye view. Since typical
HDR lightmaps are a re-mapping of two HDR images of a mirrored ball, one
90 degrees off-axis to the other, I'm confused as to how my
hemispherical image is to be rendered (or photographed). If I do a
hemispherical rendering of 0 0 0 0 0 1, I get the sky, but no ground.
Vice versa gives me the ground plane but no sky. Do I need a
hemispherical view for each cardinal heading, or something like that?
This brings me back to my original inquiry about this. Maybe Santiago
asked the question better than I did, in his recent follow-up (Hi
Santiago!):
"...is there any way to map a HDR image in a source, something in the
way skies are generated (maybe replacing the skyfunc?) and then use it
as any other sky and/or ground? Somehow, for me this seems to be the
most natural solution."
I'm imagining either an HDR photograph lightmap of the entire
model-encompasing sphere, or a Radiance image of the same type of thing,
mapped to a large sphere, in essence. Photometric accuracy of the
distribution of the light in the space, as well as the view out the
window wall are both important, so I thought this method might combine
the two. Sorry if I'm not explaining this well.
----
-RPG