Hi Christopher,

Christopher James Huff wrote:

> In article <4009d739@news.povray.org>,
>  Bill Hails <bil### [at] europeyahoo-inccom> wrote:
> 
>> I would assume that if I have two isosurfaces
>> that are coincident along a line, say the top
>> of a cylinder oriented along x touching a y plane,
>> and if I add or subtract the same noise function
>> to both isosurfaces, say f_noise3d, then the
>> resulting surfaces would still be coincident
>> (along a now distorted line).
> 
> I'm not really sure what you want. You have a cylinder resting on a
> plane, and want a deformed cylinder resting on a deformed plane?

pretty much that, yes.

> Within limits, adding noise to the cylinder function is equivalent to
> varying the radius of the cylinder, adding it to the plane function
> varies the height of the plane. I think you are expecting it to always
> move a given point on the surface in the same direction by the same
> distance. For that, you will need to perturb the coordinates given to
> the function...the easiest way would be to use warps:
> 
> function {pattern {function {...} turbulence ...}}
> 
> Apply the same warp to both isosurfaces, and they will be deformed in
> the same way.
> 

Thanks. Between you and Mike, I think I know enough to move forward.
perturb the arguments to the function rather than adding noise to
the result.

-- 
Bill Hails

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