[Radiance-general] question about sky.mat

[Thomas Bleicher]

On Mon, Jul 16, 2012 at 6:35 PM, <imenslama at voila.fr> wrote:

> Hi community,
> In radiance tutorial, for simulation of daylighting, we must create a file
> named sky.rad and an other file named sky_overcast.mat.


I don't know which tutorial you refere to but I think that the general idea
is to separate the scene elements that create the sky from the description
that defines the actual sky condition.

In Radiance you first have to define a "material" for a scene element and
then you apply this material to a geometric object like a polygone or a
disk. For the sky description there is a special type of geometry which is
called "source". This is, I expect, what you use in the sky.rad file in
your tutorial.


> But I can't find a description of the second file, I mean
> sky_overcast.mat. I know that is a material for an overcast sky but what
> should we write to define this file?


You can read the man page for gensky to get an idea of how the program is
typically used. About half way through there is an example of a complete
sky description (it starts with "!gensky 4 1 14"). Compare this with the
contents of your sky.rad file and the lines before need to go into the
sky.rad file. This may only be the "!gensky ..." line or this line and the
following "skyfunc ..." definition.

When you use this now in a scene you first add the sky_overcast.mat and
then the sky.rad file to an oconv command line to compile the octree for
the scene. When you want to use the same scene under different sky
conditions you only need to replace the sky_overcast.mat file with another
one which contains a different "!gensky ..." command to create an
intermediate or sunny sky.

Regards,
Thomas
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