Wasn't it Timothy Cook who wrote:
>I have an scene as follows,
>
>#include "functions.inc"
>#declare fn_Image=function{
>   pigment{
>     image_map{
>       tga "C:\Data\3D\POV\isotest01.tga"
>       map_type 1
>       once
>     }
>   }
>}
>isosurface{
>   function{f_sphere(x, y, z, 1)-fn_Image(x, y, z).gray}
>   contained_by{sphere{0,2.01}}
>   accuracy 0.001
>   max_gradient 100
>   pigment{color rgb 1}
>}
>
>This behaves in the follwing manner:  a sphere with radius 1 has
>extrusions based on the grey value of a pixel, with 255 extending
>1 unit from the surface of the sphere.  If I change the equation to
>
>   function{f_sphere(x, y, z, 1)+fn_Image(x, y, z).gray}
>
>(to make the grey values indentations) or reduce the radius of the
>sphere, i.e.
>
>   function{f_sphere(x, y, z, 0.5)-fn_Image(x, y, z).gray}
>
>(to decrease the size of the surface failing making indentations) all
>that results is a sphere with radius 1 and no surface distortions.
>
>How might I make working versions of formulas 2 and 3, or am I
>restricted to extruding from a base sphere of radius 1 or larger?
>


I can't reproduce your problem in either 3.5 or 3.6. Are you absolutely
sure that you didn't change anything else, like the size of the
"contained_by" sphere?

-- 
Mike Williams
Gentleman of Leisure

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