Wasn't it Carl Hoff who wrote:
>Thanks... I need all the tutorials I can find.  However yours
>leaves me a little confused...
>
>In your example you have:
>
>#declare  P = function {x*x + y + z*z - 1}
>
>isosurface {
>  function { P(x,y*(1.05-y/5),z) }
>  ...
>
>Should P be the formula of a sphere?  In which case shouldn't
>the function be x*x+y*y+z*z-1?  If that's not a typo I'm really
>confused.

Yes it's a typo. it should be y*y


>Also... a more general question...
>
>Is there a difference between these two as used in an isosurface?
>
>#declare  P = function {x*x + y*y + z*z - 1}
>isosurface {
>  function { P(x,y,z) }
>  threshold 0
>
>and
>
>#declare  P = function {x*x + y*y + z*z}
>isosurface {
>  function { P(x,y,z) }
>  threshold 1

There's no difference. Since I have a mathematical background I'm more
used to dealing with thinking about the first form.

-- 
Mike Williams
Gentleman of Leisure

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