Chris Huff <chr### [at] maccom> wrote:

> In article <3a3e0bb8@news.povray.org>, Geoff Wedig 
> <wed### [at] darwinepbicwruedu> wrote:

>> No, it gave me an error.  I don't have the code here, so I can't tell 
>> what error it was, but once I saw that, I began to wonder what 
>> eval_pattern() was for in the first place, since it wasn't for that.

> The eval_pattern() function returns the float value of a pattern at a 
> specific point...for a function pattern, this should be the result of 
> evaluating the function at that point, at least as long as the result is 
> in the 0-1 range and you don't have any special waveforms, 
> transformations, or warps applied. If you post the problem code I will 
> try to figure out what's wrong...
> Something like this macro *should* work for most cases:
> #macro Eval_Func(Func, X, Y, Z)
>     eval_pattern(function {Func}, < X, Y, Z>)
> #end
> Of course, that could also be written:
> #macro Eval_Func(Func, Pt)
>     eval_pattern(function {Func}, Pt)
> #end
> Where Pt is a 3D vector.

> The problem might be in the implementation of the isosurface 
> functions...I don't understand the code very well, but it uses a lot of 
> global variables, and may only work at render time...I've had problems 
> with it before, trying to get a function pigment to work(specifying 3 
> functions, for red, green, and blue).

Hmm, this is a deformation formula, so it ranges quite far (much further
than [0..1].  I'll check to see what error it gave when I get the chance.

Geoff

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