"marabou" <not### [at] availableyet> wrote in message 
news:454a3d41@news.povray.org...
> hello,
> I want to check if one point at spline-creation time is
> equal to one point in an array.
>  ... snip ...
>                #if ( splinepath(clock_counter) = splinepoints[10] )
>  ... snip ...
> Then comes a parse error: "Float expected but vector or color expression
> found."
> And I ask: Why is splinepath(at_one_moment) no vector? What did I wrong?
>

Hi,
splinepath(clock_counter) does return a vector, but, in an #if statement you 
need something that evaluates to a 'float expression that is interpreted as 
a boolean value' and vector1=vector2 doesn't give you that, which is why you 
get the error that complains that it came across a vector rather than 
finding a float.

I believe you'll need to test the individual elements of the vector, (though 
someone may know an easier way):

#declare A = <1,1,1>;
#declare B = <1,1,1>;
#if (A.x=B.x & A.y=B.y & A.z=B.z)
  sphere {0,1 pigment {color rgb 1}}
#end

Also, even if the condition is theoretically met, you may well run into 
precision errors that you'll need to deal with.
ie if splinepath(clock_counter) returns <1.0000001,0.999999999,1.000000005> 
then you'll need to handle that in your logic.
Typically you could end up with something like:

#declare Threshold = 0.001;
#if (A.x-B.x<Threshold &
      A.y-B.y<Threshold &
      A.z-B.z<Threshold)

Regards,
Chris B.

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