Yadgar nous apporta ses lumieres ainsi en ce 14/08/2004 07:33... :

> High!
>
> I'm not really sure whether I'm on-topic here or not... but as this 
> group also deals with programming techniques, I just assumed...
>
> My question: does PoV-Ray allow programming of "discontinuous" 
> functions (I only dabble in math, so please don't stone me if this is 
> not the correct terminus!)?
>
> Is it possible to write a function which changes apruptly at certain 
> values, such as
>
> from x=0 to x=1.5: pow(x, 2)
> from x=1.5 to x=7: sqrt(14-x)+3
> etc. etc. ?
>
> See you in Khyberspace - 
> http://home.arcor.de/yadgar/khyberspace/index-e.html
> Afghanistan Chronicle: http://home.arcor.de/yadgar/
>
> Yadgar
>
> Now playing: Deimos and Phobos go to Mars (Synergy)

It's possible but not alway a good solution. If used in an isosurface, 
it will lead to infinite gradient. It may be preferable to use an union 
of different objects, each modeled acording to a continuous function.
If used to define a path in an animation, it can lead to whatever is 
folowing that path to jump around.

In your case use a #switch:
#switch(YourVar)
    #range(0,1.5)#declare OutVar=pow(YourVar,1);#break
    #range(1.5,7)#declare OutVar=sqrt(14-YourVar)+3;#break
    #range(.....
#end

Alain

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