Shay wrote:

> If anyone else has a technique which might help, I would like to see
>your results as well. The point is to make a large height field from
>this small image map, so enlarging and smoothing the map is not allowed.

Just for fun, here are some images generated by using the source image as an
isosurface pigment function. The texture, lighting and camera are exactly
the same as your original full_resolution_hf image, so they are directly
comparable.

The "Interp4.jpg" image simply uses image_map interpolation 4.
(Interpolation 2 and no interpolation gives results which are almost
identical to smoothed and unsmoothed height_fields respectively).

#declare F=function{pigment{
  image_map { jpeg "hf_map.jpg" interpolate 4}
  }
}
#declare my_heightfield =
    isosurface {
        function { y-F(x,z,0).red }
        max_gradient 5.5
        contained_by{box{0,1}}
        open
}
object {
  my_heightfield
  pigment {rgb 1}
  translate <-.5, -.5, -.5>
  rotate y*135
}
background { rgb <1,1,1> }
camera { location <0.1,1,-1> look_at <0,0,-.08> }
light_source { <-40,180,2.5> color rgb 1 }

The "Interp2smooth.jpg" and "Interp4smooth.jpg" perform a smoothing
operation in the isosurface function as well as image_map interpolation 2
and 4 respectively. But that might be a bit of a cheat because it's
mathematically very similar to performing a Blur operation on the source
image before processing (except that the result has full floating point
precision instead of 256 bits)

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Attachments:
Download 'Interp2Smooth.jpg' (42 KB) Download 'Interp4.jpg' (64 KB) Download 'Interp4Smooth.jpg' (60 KB)

Preview of image 'Interp2Smooth.jpg'

Preview of image 'Interp4.jpg'

Preview of image 'Interp4Smooth.jpg'

"Mike Williams" <mik### [at] econymdemoncouk> wrote in message
news:3f5f5ebf@news.povray.org...

Not bad, but Hogo's mesh is smoother. Even with the blurring, the
isosurface is not able to "fudge" the bad spots as well as a mesh it
seems. The iso is simply too accurate. I should get a chance to render
mine here in a bit.

What where your render times?

 -Shay

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Wasn't it Shay who wrote:
>
>"Mike Williams" <mik### [at] econymdemoncouk> wrote in message
>news:3f5f5ebf@news.povray.org...
>
>Not bad, but Hogo's mesh is smoother. Even with the blurring, the
>isosurface is not able to "fudge" the bad spots as well as a mesh it
>seems. The iso is simply too accurate. I should get a chance to render
>mine here in a bit.
>
>What where your render times?

Very slow. The ones I posted here took 4 minutes 44 seconds each,
compared with 10 seconds for a height field. However, POV suggests a
considerably higher max_gradient than I used, but if I use the higher
max_gradient it suggests one that's considerably higher than that. At
the edges of the source image pixels the gradient is theoretically
infinite. The speed is very dependent on the value of max_gradient
chosen.

-- 
Mike Williams
Gentleman of Leisure

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Mike Williams <mik### [at] econymdemoncouk> wrote:

> Just for fun, here are some images generated by using the source image as an
> isosurface pigment function.

Here are 3 isos with bicubic interpolation.
They use different coefficients for the interpolation:

image_map
{
  png "hf_map.png" 
  interpolate 3
  #local s=2;
  #local A=.5; // other two images: A=.7 / A = 1.0 (default)
  matrix <(-1-s*A+s)/s, (-s+3*s*A-1)/s, (1-3*s*A+s)/s, (-s+1+s*A)/s,
        -1/2/s*(-4-3*s*A+3*s), -1/2/s*(-3*s+9*s*A-2), -1/2/s*(-9*s*A+4+3*s),
-1/2/s*(-3*s+2+3*s*A),
        -1/s, 0, 1/s, 0,
        1/2-1/2*A, A, 1/2-1/2*A, 0>
}

This code needs my bicubic interpolation patch to work.

Lutz-Peter

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Download 'hf_bicubic_05.jpg' (20 KB)

Preview of image 'hf_bicubic_05.jpg'

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Download 'hf_bicubic_05.jpg' (0 KB) Download 'hf_bicubic_07.jpg' (22 KB)

Preview of image 'hf_bicubic_07.jpg'

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Download 'hf_bicubic_07.jpg' (0 KB) Download 'hf_bicubic_10.jpg' (28 KB)

Preview of image 'hf_bicubic_10.jpg'