Can anybody tell me if there is a theoretical limit to the size/distance
calculations in pov?

I'm trying to do a scene inspired by the videogame Halo, but  my
gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
disappears from less than 170 miles out.  Unless i'm much mistaken, an
object that size should be vizible from several thousand miles distant.

/*
 Persistence of Vision Ray Tracer Scene Description File
 File: RingWorld.pov
 Vers: 3.5
 Desc:
 Date: 10/17/02
 Auth: Anthony D. Baye
*/

#include "colors.inc"
#include "textures.inc"

#declare ft = 12 ;
#declare mi = 5280*ft ;


camera {
 location  <0.0, 0.0, -36405.0*mi>
 look_at   <0.0, 0.0, 0.0>
 }

light_source { <0.0, 0.0, -36405.0*mi> color rgb 1.0 }

#declare Metal1 =
finish {
 roughness 0.007
    metallic
    brilliance 0.5
    ambient 0.1
    diffuse 0.4375
    brilliance 2
    reflection { 0.25 metallic fresnel on }
    phong 0.5
    phong_size 175
    conserve_energy
 }

object {
 union {
  sphere { 0.0, 36250.0*mi }
/*  difference {
   torus { 4000.0*mi, 1000.0*mi  }
//   torus { 4000.0*mi, 997.0*mi texture { T_Gold_5A } }
   cylinder { <0.0, -1000.00390625*mi, 0.0> <0.0, 1000.00390625*mi, 0.0>
4994.98731061*mi }
    pigment { Red*0.4375 }
    finish { Metal1 }
     rotate <72, 18.0, 0.0>
     translate <0.0, 0.0, -200000.0*mi>
//     rotate <0.0, 18.0, -6.0>
   }*/
  }
  pigment { White*0.625 }
 }

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In article <3DAEFA2A.DC167FA4@Rapidnet.com> , "Anthony D. Baye" 
<ban### [at] Rapidnetcom> wrote:

> Can anybody tell me if there is a theoretical limit to the size/distance
> calculations in pov?
>
> I'm trying to do a scene inspired by the videogame Halo, but  my
> gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
> disappears from less than 170 miles out.  Unless i'm much mistaken, an
> object that size should be vizible from several thousand miles distant.

Try metric units and set one POV-unit as one km.  IIRC there is some FAQ
answer about your star system construction mistake...

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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Anthony D. Baye <ban### [at] rapidnetcom> wrote:
> Can anybody tell me if there is a theoretical limit to the size/distance
> calculations in pov?

> I'm trying to do a scene inspired by the videogame Halo, but  my
> gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
> disappears from less than 170 miles out.  Unless i'm much mistaken, an
> object that size should be vizible from several thousand miles distant.

  The accuracy of floating point numbers is limited.
  With such extreme scales you are probably exceeding the accuracy limits
needed for proper raytracing by a whole lot.
  You will have to use a much bigger value as unit (such as 1 km or more).

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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> I'm trying to do a scene inspired by the videogame Halo, but  my
> gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
> disappears from less than 170 miles out.  Unless i'm much mistaken, an
> object that size should be vizible from several thousand miles distant.


Heh, as others have pointed out, 170 miles is a whooooole lotta inches.
Thorsten and Warp have suggested that you change your scale. If, for some
reason, you don't want to change your scale (for instance, if you have a
small model of a telescope in the foreground that is only a few inches
long), then you may want to simple decrease the size of the planet by x
amount, and decrease its distance by x amount. For instance, if the planet
is 1000 km in diameter and 10000 km away, then just make it 1 km in
diameter, 10 km away. The difference will most likely be unnoticeable from a
stationary viewpoint.

 - Slime
[ http://www.slimeland.com/ ]

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Warp wrote:
> Anthony D. Baye <ban### [at] rapidnetcom> wrote:
> 
>>Can anybody tell me if there is a theoretical limit to the size/distance
>>calculations in pov?
> 
> 
>>I'm trying to do a scene inspired by the videogame Halo, but  my
>>gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
>>disappears from less than 170 miles out.  Unless i'm much mistaken, an
>>object that size should be vizible from several thousand miles distant.
> 
> 
>   The accuracy of floating point numbers is limited.
>   With such extreme scales you are probably exceeding the accuracy limits
> needed for proper raytracing by a whole lot.

I don't think, that this is due to accuracy problems with floating 
points. 170 miles is 1.07E07 inches and this exceeds just a little bit 
value of Max_Distance (1.0e7), which is maximum distance for ray-object 
intersection (according to comment in frame.h)

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"Anthony D. Baye" wrote:

> Can anybody tell me if there is a theoretical limit to the size/distance
> calculations in pov?
>
> I'm trying to do a scene inspired by the videogame Halo, but  my
> gas-giant is the size of Jupiter (1 unit = 1 inch.) yet it copletely
> disappears from less than 170 miles out.  Unless i'm much mistaken, an
> object that size should be vizible from several thousand miles distant.
>
> /*
>  Persistence of Vision Ray Tracer Scene Description File
>  File: RingWorld.pov
>  Vers: 3.5
>  Desc:
>  Date: 10/17/02
>  Auth: Anthony D. Baye
> */
>
> #include "colors.inc"
> #include "textures.inc"
>
> #declare ft = 12 ;
> #declare mi = 5280*ft ;
>
> camera {
>  location  <0.0, 0.0, -36405.0*mi>
>  look_at   <0.0, 0.0, 0.0>
>  }
>
> light_source { <0.0, 0.0, -36405.0*mi> color rgb 1.0 }
>
> #declare Metal1 =
> finish {
>  roughness 0.007
>     metallic
>     brilliance 0.5
>     ambient 0.1
>     diffuse 0.4375
>     brilliance 2
>     reflection { 0.25 metallic fresnel on }
>     phong 0.5
>     phong_size 175
>     conserve_energy
>  }
>
> object {
>  union {
>   sphere { 0.0, 36250.0*mi }
> /*  difference {
>    torus { 4000.0*mi, 1000.0*mi  }
> //   torus { 4000.0*mi, 997.0*mi texture { T_Gold_5A } }
>    cylinder { <0.0, -1000.00390625*mi, 0.0> <0.0, 1000.00390625*mi, 0.0>
> 4994.98731061*mi }
>     pigment { Red*0.4375 }
>     finish { Metal1 }
>      rotate <72, 18.0, 0.0>
>      translate <0.0, 0.0, -200000.0*mi>
> //     rotate <0.0, 18.0, -6.0>
>    }*/
>   }
>   pigment { White*0.625 }
>  }

I would like to do a flyby to come in through the athmosphere of the ring
world in orbit, thus the reason for my large scale, but if there is a
problem with the scale calulations, I can try deviding by tyhe scale
definitions instead of multiplying by them.  Thus the scene is smaller.


A.D.B

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