Hi everybody,

I have a bitmap I want to project onto the surface of a sphere. I want to use
spherical projection, so that the image is not distorted. The problem is that I
want to control the angle covered (measured from the center of the sphere). One
solution would be to increase the bitmap size with nothing around, but that is
ugly. What is the correct way to do this?

Another question: I am using a bitmap obtained from a postscript file I have,
because I did not find the way to use the PS directly. Is it possible?

Thanks in advance.

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"zeycus" <mig### [at] onocom> wrote in message 
news:web.47a44adec0e4bb1b5f201c20@news.povray.org...
> Hi everybody,
>
> I have a bitmap I want to project onto the surface of a sphere. I want to 
> use
> spherical projection, so that the image is not distorted. The problem is 
> that I
> want to control the angle covered (measured from the center of the 
> sphere). One
> solution would be to increase the bitmap size with nothing around, but 
> that is
> ugly. What is the correct way to do this?
>

Hi,

Use the 'once' keyword and scale in 'x'  to get a segment (or scale in 'y' 
and translate in 'y' to get a ring around the middle of the sphere).

light_source { <-15,7.5,-15>, rgb 2}
camera {location <0,3,0> look_at <0,0,0>}

sphere {0,1
  texture {
    pigment {
      image_map {sys "ngtest11.bmp" once}
      scale 0.6*x
      rotate x*90
      warp {spherical
        orientation y
        dist_exp 1
      }
    }
  }
}


> Another question: I am using a bitmap obtained from a postscript file I 
> have,
> because I did not find the way to use the PS directly. Is it possible?
>

No. The valid bitmap types are "gif | tga | iff | ppm | pgm | png | jpeg | 
tiff | sys".
No vector graphics formats are supported.

Regards,
Chris B.

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zeycus <mig### [at] onocom> wrote:
> I have a bitmap I want to project onto the surface of a sphere. I want to use
> spherical projection, so that the image is not distorted. The problem is that I
> want to control the angle covered (measured from the center of the sphere). One
> solution would be to increase the bitmap size with nothing around, but that is
> ugly. What is the correct way to do this?

  Apply this tip using the spherical warp:

http://tag.povray.org/povQandT/languageQandT.html#cylindricalrepeat

-- 
                                                          - Warp

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"Chris B" <nom### [at] nomailcom> wrote:
> "zeycus" <mig### [at] onocom> wrote in message
> news:web.47a44adec0e4bb1b5f201c20@news.povray.org...
> > Hi everybody,
> >
> > I have a bitmap I want to project onto the surface of a sphere. I want to
> > use
> > spherical projection, so that the image is not distorted. The problem is
> > that I
> > want to control the angle covered (measured from the center of the
> > sphere). One
> > solution would be to increase the bitmap size with nothing around, but
> > that is
> > ugly. What is the correct way to do this?
> >
>
> Hi,
>
> Use the 'once' keyword and scale in 'x'  to get a segment (or scale in 'y'
> and translate in 'y' to get a ring around the middle of the sphere).
>
> light_source { <-15,7.5,-15>, rgb 2}
> camera {location <0,3,0> look_at <0,0,0>}
>
> sphere {0,1
>   texture {
>     pigment {
>       image_map {sys "ngtest11.bmp" once}
>       scale 0.6*x
>       rotate x*90
>       warp {spherical
>         orientation y
>         dist_exp 1
>       }
>     }
>   }
> }
>

Thank you, this is exactly what I was looking for. I did not know the warp
command, that was my problem.

>
> > Another question: I am using a bitmap obtained from a postscript file I
> > have,
> > because I did not find the way to use the PS directly. Is it possible?
> >
>
> No. The valid bitmap types are "gif | tga | iff | ppm | pgm | png | jpeg |
> tiff | sys".
> No vector graphics formats are supported.
>

A pitty. Maybe not many people would use it, I don't know, but for me it would
be useful!

Post a reply to this message

"zeycus" <mig### [at] onocom> wrote in message 
news:web.47a5dc66a2a0ea67b5f201c20@news.povray.org...
> "Chris B" <nom### [at] nomailcom> wrote:
>> Use the 'once' keyword and scale in 'x'  to get a segment (or scale in 
>> 'y'
>> and translate in 'y' to get a ring around the middle of the sphere).
>>
>
> Thank you, this is exactly what I was looking for. I did not know the warp
> command, that was my problem.
>

Looking at the link Warp posted, I think you should be able to do the same 
with Map Type 1 and avoid the need for the Warp, but I've not tried that 
myself.

Regards,
Chris B.

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