Le 11/02/2015 04:13, Mike Horvath a écrit :
> Has anyone written a function for a caternaroid(?) that works just like
> Paraboloid_Z in shapes_old.inc?

I'm afraid not: Paraboloid_Z is a quadric, but a caternaroid (do you 
mean something like a Pringles) would need something like cosh in the 
equation.

http://bennbatt.tumblr.com/

  z = A.cosh(x) - B.cosh(y)

Now, I might just be wrong, because the displayed equation

z = x²/a² -y²/b² with x²/a²+y²/b² < 1 would be something easy on a 
quartic, with intersection of a cylinder along z for the <1 part.

// create a quadratic (2nd order) infinite polynomial surface
quadric {
   <1, -1, 0> //  A x^2  + B y^2  + C z^2  +
   <0, 0, 0> //  D xy   + E xz   + F yz   +
   <0, 0, -1> //  G x    + H y    + I z    +
   0         //  J
}


-- 
Just because nobody complains does not mean all parachutes are perfect.

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