Maybe someone else has tried this, or maybe I'm alone in my stupidity
but I tried to render an earth to scale 1pov unit = 1 meter which of
course comes
out to a mean value of 12,756 km in diameter or 6,378,000m as a sphere
radius.
Also, I put my light source(the sun) at <0,0,0> and then moved my earth
sphere
to <0,0,149600000000>(mean distance from sun).

1.What is the limit? How many places can I carry out my numbers around
the decimal point?

2.Why does the earth appear to have a grainy texture when it is only has
a blue
pigment? Scale is beyond pov's capabilities?

3.I was surprised that the earth was actually lit up at that distance.
Is this because
there is no falloff in the point lightsource?

4.I also wanted to be able to rotate the camera around the earth but
couldn't
seem to make it work. I tried rearanging the order of the code with
rotate
before or after translate to no avail. How would this be accomplished?

Note: I know doing it at this size really isn't necessary. I just wanted
to give it a shot!

Heres my source:

#version 3.1;
#include "colors.inc"

global_settings{
     assumed_gamma 1.0
}
// ----------------------------------------
camera{
     location  <0.0, 0.0,149600000000.0>
     direction <0, 0, 1>
     right     <1.33, 0, 0>
     translate <0.0, 0.0, -13500000.0>
     //rotate y*.001
     look_at   <0.0, 0.0, 149600000000.0001>
     }
light_source{
     0*x                // light's position (translated below)
     rgb <1.0,1.0,1.0>*2//pow(10,10)
     //translate <0,0,14959930000.0>
}
// ----------------------------------------
background{Black}
sphere{<0,0,0>,6378000.0
     pigment{Blue}
     translate<0,0,149600000000.0>
}
--
...coffee?...yes please! extra sugar,extra cream...Thank you.

Post a reply to this message

Phil Clute wrote:
> 
> Maybe someone else has tried this, or maybe I'm alone in my stupidity
> but I tried to render an earth to scale 1pov unit = 1 meter which of
> course comes
> out to a mean value of 12,756 km in diameter or 6,378,000m as a sphere
> radius.
> Also, I put my light source(the sun) at <0,0,0> and then moved my earth
> sphere
> to <0,0,149600000000>(mean distance from sun).
> 
> 1.What is the limit? How many places can I carry out my numbers around
> the decimal point?

 Whatever your system's epsilon will support. I forget what the numbers
are on a system by system basis. There was a mention that the Pov team made
a change increasing the value it now supports in the release of Pov v3.15e
They had choosen a lower valu previously and many users complained so they
extended it's capability some. Check in the announcements group and see
if the release notes give the upper value for that.

> 2.Why does the earth appear to have a grainy texture when it is only has
> a blue
> pigment? Scale is beyond pov's capabilities?

Posibility.
 
> 3.I was surprised that the earth was actually lit up at that distance.
> Is this because
> there is no falloff in the point lightsource?

Yes.
 
> 4.I also wanted to be able to rotate the camera around the earth but
> couldn't
> seem to make it work. I tried rearanging the order of the code with
> rotate
> before or after translate to no avail. How would this be accomplished?

camera { location < 0, 0, -120,000,000> look_at 0 rotate y*360 }
 
> Note: I know doing it at this size really isn't necessary. I just wanted
> to give it a shot!

Bob Hughs did a rather extensive study on this issue of distance within
the last 3-4 months or so. I forget where he psted his results but
a little searching should be able answer your questions in more detail.

It was probably posted to this group. If not look in
.tutorials
.windows
.scene-files

-- 
Ken Tyler

mailto://tylereng@pacbell.net

Post a reply to this message

Yep, the size of different primitives cause differing effects. Though
the scaling testing I was carrying out was based on the other epsilon
value for Windows and DOS, that being 10,000,000 if I remember right.
And the scaling test was actually created by another person, and I
forgot the name, but believe it was at c.g.r.r. Ingeniously he scaled
both camera and objects together. I just reformatted the script some.
Here it is again:

// this shows several basic primitives at various sizes
// for epsilon value 10,000,000 in POV-Ray for Windows 3.0 version
// this has since been changed for 3.1d, 3.1e
// Note: Watch For Line Wrap!

#include "colors.inc"

//#declare SCALE = 1
 // at 1 normal.

#declare SCALE0 = 0.000000001
 // at .000000001 the cone remains normal! (gone in version 3.*?)
#declare SCALE1 = 0.00000666
 // at .0000066 the torii are chopped! no spheres or blobs.
#declare SCALE2 = 0.0031624
 // at .0031623 the spheres shrink out of sight (640x480)!
#declare SCALE3 = 44444
 // above 36000 the box distorts!
#declare SCALE4 = 666666
 // at 666666 the torii are cut in (opposite) half! blobs need sturm. no
box.
#declare SCALE5 = 999999999
 // at 999999999 the cone is indestructable (not in 3.*?)! spheres gone
again. no box, blobs or torii.

#declare SCALES = SCALE0  // replace # with 0-5

#declare OBJ = union{
cylinder {-y,y,1 rotate <30,45,30> pigment {Red}}
sphere {0,1 translate <0,-2.5,0> pigment {Green}}
sphere {0,1 translate <0,2.5,0> pigment {Yellow}}
cone {-y,1,y,0 rotate <30,30,30> translate <-3,0,0> pigment {Red}}
torus {1,.25 rotate <45,15,30> translate <3,-2.5,0> pigment {White}}
torus {1,.25 rotate <-45,-15,-30> translate <3,2.5,0> pigment {Black}}
box {<-.8,-.8,-.8>,<.8,.8,.8> rotate <45,45,45> translate <3,0,0>
 pigment {Red}}
blob {threshold .5
 sphere	{-x,1.25,.75 pigment {Green}}
 sphere	{x,1.25,.75 pigment {Yellow}}
 cylinder {-y,y,1.25,.75 pigment {DarkPurple}}
  rotate <-40,-30,-20> translate <-3,-2.5,0> sturm}
blob {threshold .5
 sphere	{-x,1.25,.75 pigment {Blue}}
 sphere	{x,1.25,.75 pigment {Orange}}
 cylinder {-y,y,1.25,.75 pigment {Pink}}
  rotate <40,30,20> translate <-3,2.5,0> sturm}
}
camera		{ location <0,0,-15> look_at <0,0,0> angle 40 scale SCALES }
light_source{ <+100,+100,-1000> color rgb<1.5,1.5,1.5> scale SCALES }
background	{ color Gray}
object		{ OBJ scale SCALES }

//END


Ken wrote:
> 
> Phil Clute wrote:
> >
> > Maybe someone else has tried this, or maybe I'm alone in my stupidity
> > but I tried to render an earth to scale 1pov unit = 1 meter which of
> > course comes
> > out to a mean value of 12,756 km in diameter or 6,378,000m as a sphere
> > radius.
> > Also, I put my light source(the sun) at <0,0,0> and then moved my earth
> > sphere
> > to <0,0,149600000000>(mean distance from sun).
> >
> > 1.What is the limit? How many places can I carry out my numbers around
> > the decimal point?
> 
>  Whatever your system's epsilon will support. I forget what the numbers
> are on a system by system basis. There was a mention that the Pov team made
> a change increasing the value it now supports in the release of Pov v3.15e
> They had choosen a lower valu previously and many users complained so they
> extended it's capability some. Check in the announcements group and see
> if the release notes give the upper value for that.
> 
> > 2.Why does the earth appear to have a grainy texture when it is only has
> > a blue
> > pigment? Scale is beyond pov's capabilities?
> 
> Posibility.
> 
> > 3.I was surprised that the earth was actually lit up at that distance.
> > Is this because
> > there is no falloff in the point lightsource?
> 
> Yes.
> 
> > 4.I also wanted to be able to rotate the camera around the earth but
> > couldn't
> > seem to make it work. I tried rearanging the order of the code with
> > rotate
> > before or after translate to no avail. How would this be accomplished?
> 
> camera { location < 0, 0, -120,000,000> look_at 0 rotate y*360 }
> 
> > Note: I know doing it at this size really isn't necessary. I just wanted
> > to give it a shot!
> 
> Bob Hughs did a rather extensive study on this issue of distance within
> the last 3-4 months or so. I forget where he psted his results but
> a little searching should be able answer your questions in more detail.
> 
> It was probably posted to this group. If not look in
> .tutorials
> .windows
> .scene-files
> 
> --
> Ken Tyler
> 
> mailto://tylereng@pacbell.net

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/homepage.htm
 mailto:inv### [at] aolcom?Subject=PoV-News

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Hello Phil,
just a try to help you rotate the camera:

camera{
  location <0,0,6378000+600000> // 600000 is the distance from the 				
// earth, so the total distance from the 				// center of the earth is
6378000+600000
  rotate x*angle		// angle is any number (mostly 				// numbers between
0-360 are used)
  translate <0,0,149600000000.0> // now the camera should be behind
the 				 // earth when an angle of 0 is used
  look_at <0,0,149600000000.0>	
}

If this doesn't work(I haven't tried out yet), try this:

camera{
  location
<60000*sin(angle*pi/180),0,149600000000+(6378000+600000)*cos(angle*pi/180)>
  look_at <0,0,149600000000.0>
}

This is a bit more complicated, but it should REALLY work

Phil Clute schrieb:
> 
> Maybe someone else has tried this, or maybe I'm alone in my stupidity
> but I tried to render an earth to scale 1pov unit = 1 meter which of
> course comes
> out to a mean value of 12,756 km in diameter or 6,378,000m as a sphere
> radius.
> Also, I put my light source(the sun) at <0,0,0> and then moved my
> earth
> sphere
> to <0,0,149600000000>(mean distance from sun).
> 
> 1.What is the limit? How many places can I carry out my numbers around
> the decimal point?
> 
> 2.Why does the earth appear to have a grainy texture when it is only
> has
> a blue
> pigment? Scale is beyond pov's capabilities?
> 
> 3.I was surprised that the earth was actually lit up at that distance.
> Is this because
> there is no falloff in the point lightsource?
> 
> 4.I also wanted to be able to rotate the camera around the earth but
> couldn't
> seem to make it work. I tried rearanging the order of the code with
> rotate
> before or after translate to no avail. How would this be accomplished?
> 



> Note: I know doing it at this size really isn't necessary. I just
> wanted
> to give it a shot!
> 
> Heres my source:
> 
> #version 3.1;
> #include "colors.inc"
> 
> global_settings{
>      assumed_gamma 1.0
> }
> // ----------------------------------------
> camera{
>      location  <0.0, 0.0,149600000000.0>
>      direction <0, 0, 1>
>      right     <1.33, 0, 0>
>      translate <0.0, 0.0, -13500000.0>
>      //rotate y*.001
>      look_at   <0.0, 0.0, 149600000000.0001>
>      }
> light_source{
>      0*x                // light's position (translated below)
>      rgb <1.0,1.0,1.0>*2//pow(10,10)
>      //translate <0,0,14959930000.0>
> }
> // ----------------------------------------
> background{Black}
> sphere{<0,0,0>,6378000.0
>      pigment{Blue}
>      translate<0,0,149600000000.0>
> }
> --
> ...coffee?...yes please! extra sugar,extra cream...Thank you.

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