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)

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