[Radiance-general] Rendering of Gensky

[Thomas Bleicher]

On Sat, Mar 13, 2010 at 5:11 PM, Brajesh Lal <brajeshlal at yahoo.com> wrote:
> Hi,
>
> I am using gensky ( Code given below) to illuminate an outdooe scene. Camera
> is looking upward.
> When i render the scene using  rpict into hdr. Why I am able to see the sun
> but not sky ?  I comes out to be black.

Gensky only produces the distribution function for the sky but nothing
it is applied to. The "sun" is created as a source but not the sky
dome (see below).

> # gensky 3 7 10:30CET +s -a 57.013056 -o -9.988333
> # Local solar time: 9.98
> # Solar altitude and azimuth: 22.4 -32.9
> # Ground ambient level: 11.1

These lines are just comments with useful stuff about the sky. The do
not contribute to the scene.

> void light solar
> 0
> 0
> 3 5.49e+06 5.49e+06 5.49e+06
>
> solar source sun
> 0
> 0
> 4 0.502204 -0.776482 0.380614 0.5

These two groups define a 'light material' called 'solar' and apply
this material to the geometry type 'source' to produce the 'sun'.

> void brightfunc skyfunc
> 2 skybr skybright.cal
> 0
> 7 1 5.04e+00 1.02e+01 3.47e-01 0.502204 -0.776482 0.380614

As above this group defines a material that describes the light
distribution over the sky dome. What's missing is a geometry it can be
applied to. I assume you have used gensky on the command line and
saved the output to a file. Add the following lines at the end of the
file:

# basic glow material for sky; brightness is defined by 'skyfunc'
skyfunc glow skyglow
0
0
4 1 1 1 0

# sky dome: 'source' type with skyglow material covering upper hemisphere
skyglow source sky
0
0
4 0 0 1 180

# material for ground; use same brightness function but reduced to 10 percent
skyfunc glow groundglow
0
0
4 0.1 0.1 0.1 0

# apply 'groundglow' to source covering the lower hemisphere
groundglow source ground
0
0
4 0 0 -1 180

# end of sky and ground description

Regards,
Thomas