Rarius nous apporta ses lumieres en ce 03-05-2007 12:29:
> In general I like your idea of putting the camera in the position of the 
> solar panel, but I am afraid that this would only give a first approximation 
> to the true value.
> 
> It would be OK if the sun's position (declination) moved in a linear 
> fashion, but it doesn't. It is much more like a sine wave. It starts off 
> moving slowly at the southernmost point (23.5 S) and accellerates northwards 
> until it crosses the equator when it starts to slow down until it stops at 
> its northernmost position (23.5 N)...  The band 0 to 1 deg will have the sun 
> in it a lot less than the band +20 to +21 deg!
You can use a gradient patern using sin_wave, darker in the middle, brighter at 
the edges.
> 
> To correct for this you could either pigment the sky band, or position 
> several thousand "suns" along it to simulate the differing light "density" 
> coming from the different bands of the sky.
> 
> Another point, you'd need a camera with more than 180deg field to do this in 
> one pass... Although it shouldn't be too difficult to do it in segments.
In POV-Ray, the camera can have a 360 degrees field. In fact, you can make the 
field any thing you want, 720 degrees is OK!
Want a fish eye view of 200 degrees?

   camera
{
   fisheye
   up y // default, optional
   right x // to make a circular image
   location 0 // start at the origin to get a simpler rotation, default 
location, optional
   angle 200 // a 200 degrees field of view
   look_at z // default direction, optional
   rotate -90*x //look up
   translate Your_Location // To place the camera where you want it
}

> 
> Rarius
> 
> "Grassblade" <nomail@nomail> wrote in message 
> news:web.4639bbc01bad02ca6955f970@news.povray.org...
>> "MustardMan" <nomail@nomail> wrote:
>>> Hi,
>>>
>>> I am using POVray to simulate the energy produced by solar panels at
>>> different orientations on a roof. My simulation includes the horizon, so
>>> the shadowing difference between summer & winter is realistic (as well as
>>> throughout the day).
>>>
>>> I can calculate the power generated by the panels by simply using some 
>>> maths
>>> and the Az & Al variables generated by SUNPOS. However, this does not
>>> include shadowing caused by objects (horizon, trees, etc) - the value is
>>> what the panels would produce if they were always illuminated.
>>>
>>> Am I able to specify a point in the scene and get POVray to report the
>>> amount of light reaching that point?
>>>
>>> Cheers,
>>> MM.
>> In six months the sun appears to move at dawn from south to north. The 
>> area
>> covered by the sun in those six months is more or less an inclined band
>> that you can simulate by intersecting a sphere with an equivalently
>> inclined cylinder. You can get the cylinder thickness in Sunpos.inc, by
>> determining the hour of dawn on winter's solstice, and then sun's position
>> at the same hour on summer's solstice. The only shadows that can possibly
>> fall on the panel (apart from clouds, that is) are the objects that lay on
>> the band's path. So I would reverse the perspective: put the camera on the
>> panel and point at the horizon; remove all textures from the potentially
>> shading objects, make the band white, and make background transparent with
>> +ua. Render and check in the Gimp (histogram) how much white you have
>> compared to the sum of black and white. Repeat for other horizon, if
>> necessary. Don't forget to add the rest of the sunpath not covered by
>> shadows. ;) And then double the value, since this is valid for six months.
>>
>>
>>
>>
> 
> 


-- 
Alain
-------------------------------------------------
Just remember - if the world didn't suck, we would all fall off.

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