Am 28.12.2013 14:41, schrieb Louis:
> After reading some tutorials and viewing examples I thought I understood
> isosurfaces, however when trying to create them myself, I run into problems.
>
> I understand that function {(x*x + y*y + z*z - 1)} would create a sphere, but
> why doesn't function {(x*x + y*y + z*z + 1)} (plus instead of minus)?
>
> According to my reasoning it should generate exactly the same sphere, using plus
> or minus should not make any difference in this formula, it only mirrors the
> coordinates which results in the same sphere right?
>
> What am I missing?

The isosurface's surface is the set of all points satisfying f(x,y,z)=0. 
(That is, unless a different threshold than 0 is specified.)

The set of solutions to the equation

     x^2 + y^2 + z^2 - 1 = 0

is the set of all points having a distance of 1 to the coordinate origin 
- in other words, the surface of the unit sphere.

The equation

     x^2 + y^2 + z^2 + 1 = 0

has no solutions at all (in the domain of real numbers, to be precise), 
as any number squared is >= 0, so the left side of the equation is 
always >= 1.

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