restricting Plot3D to defined domain



>>>>> "Gary" == Gary Ruben <gazzar@email.com> writes:

    Gary> Hi,
    Gary> I'm trying to get a 3D plot of a hemisphere by doing the following:

    Gary> plot3d(realpart(sqrt(25-x^2-y^2)),[x,-5,5],[y,-5,5],[grid,50,50]);

    Gary> Why doesn't this work? Is there a different way besides my
    Gary> inclusion of realpart of restricting the domain to defined
    Gary> regions?

In what way does this not work?  Your plot3d command works for me,
except that it prompts me for the sign of y^2+x^2-25.  Since maxima
can work with complex numbers and will do so in this case, realpart
seems a reasonable solution.  

Alternatively, define a new function that does what you want, or use
some other parametric definition of the hemisphere.

Will that work?

Ray