Quadric Surfaces
1. ellipsoid
> with(plots):
> implicitplot3d((x^2)+(y^2)/4+z^2=1,x=-1..1,y=-2..2,z=-1..1);
2. elliptic cone
> implicitplot3d((x^2)+(y^2)/4=z^2,x=-1..1,y=-2..2,z=-1..1,style=patchcontour);
3. hyperboloid of one sheet
> implicitplot3d((x^2)+(y^2)/4-(z^2)=1,x=-4..4,y=-5..5,z=-2..2,axes=normal);
4. elliptic paraboloid
> implicitplot3d((x^2)+(y^2)/4=z,x=-1..1,y=-2..2,z=0..1,style=patchnogrid);
5. hyperboloid of two sheet
> implicitplot3d((x^2)+(y^2)-(z^2)/4=-1,x=-3..3,y=-4..4,z=-4..4,axes=normal);
6. hyperbolic paraboloid
> implicitplot3d((x^2)-(y^2)=z,x=-2..2,y=-3..3,z=-2..2,style=patchnogrid);