FexFX nous apporta ses lumieres en ce 08-03-2007 12:37:
> "Bill Pragnell" <bil### [at] hotmailcom> wrote:
>> "FexFX" <fex### [at] comcastnet> wrote:
>>> Are there built in limits to size and distance in povray?
>>> There seems to be...
>> Things can get dicey when you reach solar system proportions. See this
>> thread:
>>
>>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.4360929f30852916731f01d10%40news.povray.org%3E/?mtop=3
>>
>> for a lengthy discussion (and partial solution) to this problem when some of
>> us tried to produce a Ringworld (a big dumb object from Larry Niven's SF
>> novel of the same name).
>>
>> Bill
> 
> Thanks for the link...Looks like I may be up against a wall on an even
> slammer scale than ringworld scales...
> I have bult a space station (small and retro-sci-fi styled) using 1 unit = 1
> foot as a scale...
> Then I placed a "Jupiter" like object behind it which is roughly 350k units
> distant Z and 250k Units Radius...the problem is that the Stars cannot be
> more than 500k out...which means that the back edge of "jupiter" is hitting
> the stars...
> This causes some obvious issues...
> Any suggestions beyond rescallign everything so that 1 unit = 100 miles and
> then resizing jupiter, the space station, and everything else and leaving
> the stars at 500K units?
> 
> 
Scale down "Jupiter" by a factor of 100 or 1000 and put it 100 or 1000 times closer.
Do away with your stars and substitute a sky_sphere. It never receive any 
shadow. Or you may use a "world sphere" about 400K unit radius with 
finish{ambient 1 diffuse 0} that will not show any shadow and don't need any 
light to be seen.

-- 
Alain
-------------------------------------------------
If Barbie is so popular, why do you have to buy her friends?

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In practice, any number greater than 100k, or less than
0.001 in pov is asking for floating point problems.

The apparent scaling of an object varies linearly in
relation to the camera.
So if you move an object along a vector from
the actual location toward the camera to 10% of its
actual distance, the object should be 10% of its
actual size to look the same. In other words if
the ratio of the radius to the distance is the same
the object will appear the same size.

Here's a sample...
camera {
   location <0,0,-4>
   direction 1.5*z
   right     x*image_width/image_height
   look_at   <0.0, 0.0,  0.0>
}
sphere {<0,0,0>, 1
   texture {
      pigment{rgb <1,0,0>}
      finish{ambient 1}
   }
   #local SC = 0.5; //should look the same no matter what number SC is
   scale SC
   translate SC*4*z-4*z
}

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