I added a wood image over a big floor mapping a texture. The code of my material
is:

material {
  texture {
    uv_mapping pigment {
      image_map {
        tiff "wood.tif"
        interpolate 2
      }
    }
    finish {
      ambient 1
      diffuse 1
    }
  }
}

Texture repeats over the floor, and the result is ok in near distances, but
jittering appears in texture when distance increases.

I tried changing interpolation value, and using 0 (no interpolation), 2 or 4
always render the same image...

What can be the cause of interpolation failing?

Thanks for your help.

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I think you're confusing texture interpolation with mipmapping. Texture 
interpolation, what "interpolate" does, is only visibly if 1 
texture-pixel (texel?) fills more than 1 screen-pixel (screxel?). 
Mipmapping (not natively supported by POV-Ray) kicks in when the 
opposite is true.

It is possible to simulate mipmapping in POV-Ray, but it's not very easy 
and doesn't work under all circumstances. It's much easier (but possibly 
much slower) to just use higher anti-aliasing settings.

-- 
ZK

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> I added a wood image over a big floor mapping a texture. The code of my material
> is:
>
> material {
>    texture {
>      uv_mapping pigment {
>        image_map {
>          tiff "wood.tif"
>          interpolate 2
>        }
>      }
>      finish {
>        ambient 1
>        diffuse 1
>      }
>    }
> }
>
> Texture repeats over the floor, and the result is ok in near distances, but
> jittering appears in texture when distance increases.
>
> I tried changing interpolation value, and using 0 (no interpolation), 2 or 4
> always render the same image...
>
> What can be the cause of interpolation failing?
>
> Thanks for your help.
>
>

What you see is caused by the details of your image becoming to small, 
sub pixel. In that case, anti-aliasing is often not enough.

You can hide it by using gocal blur. Use a small aperture value, less 
than 1% of the camera-focal point distance. As the camera get jittered 
around, it will catch and average those very small, sub pixel, details.




Alain

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