On 9/8/2016 2:16 AM, Le_Forgeron wrote:
> Le 08/09/2016 à 03:54, Mike Horvath a écrit :
>> I'm trying to create the Sun in my scene. However I am having trouble
>> getting it to be the rights size. Here is what I'm doing:
>>
>> #include "sunpos.inc"
>> #declare Meters            = 60;        // 60 units = 1 meter.
>> #declare SunRadius        = 695700000 * Meters;
>> #declare SunDistance        = 1.4960e11 * Meters;
>> #declare Source_Distance    = 100000 * Meters;
>> #declare Source_Location    = SunPos(2016, 9, 6, 11, 0, 0, 39.7684, 0);
>> #declare Source_Location    =
>> vnormalize(<+Source_Location.x,-Source_Location.y,+Source_Location.z>) *
>> Source_Distance;
>>
>> // Either this or the next line
>> //#declare Source_Radius        = Source_Distance/SunDistance *
>> SunRadius;
>> // This is the next line
>> #declare Source_Radius        = tand(4/15) * Source_Distance;
>>
>> As you can see I tried two methods. They produce similar results as far
>> as I can tell. But to me the Sun still seems too small.
>>
>> Look at the scene here:
>>
>> http://isometricland.net/panorama/pannellum.htm?config=pano_lego_carriagehouse.json
>>
>>
>>
>> What am I doing wrong? Are my eyes wrong?
>>
>
> The data might not be what they stand for.
> The sun should appears to be about 32 minutes of arc, that's nearly half
> a degree.
> So your tand(4/15) is kind of correct ( 8/15 for the diameter )
>
> That would be correct within a scene with a viewing angle of 10° : big
> sun when you focus on something, with enough clouds to allow you to star
> at the sun.
>
> With a naked sky, you cannot star at the sun (you should not, or you
> will be blind soon), and you might think it is bigger. But you do not
> see it really.
>
> Back to your question: it is all in the brain, and you get badly
> influenced by pictures and movies which zoomed the sun and the moon for
> dramatic effects.
>
> Half a degree, it's all of its apparent diameter; But it's 10% of a 5°
> focus!
>
> Binoculars which do x16 would display 3.5° as 56°
> (notation of binoculars are G x D, G is the multiplier of the angle, and
> D the diameter of the input lens)
>

Thanks! I found this thread that discusses the same sort of things:

http://news.povray.org/povray.binaries.images/thread/%3C51b18d7d%40news.povray.org%3E/


Mike

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