easiest way to do the first one is an edge srf. I drew 4 adjacent circles, and then trimmed at the tangent points. Jointed the curves, and then used control points to bend them in the x direction. then I exploded the curves and used them to create an edge srf.
the second shape is a little more work, but i laid out a polar array of circles around a central circle (the top of the cone). then trimmed the array circles at tangents. then circumscribed a circle around the trimmed array. next i moved the center circle in he x direction, and connected it to the circumscribed circle with a 2 pt arc. then revolve, and trim the shape using the polar array. shape_sample.3dm (99.6 KB)
Maybe a slightly easier method for the first shape: The saddle is a piece of an hourglass shape: revolve an hourglass, make your “diamond” shape curve (follow asbeastos’s directions to create that), and then project that curve onto the hourglass and trim the rest away. Starting with an hourglass will give you a “truer” saddle IMHO.
For the sloped cone, I would revolve an arc curve, then array some cylinders around the base. Intersect the shapes and use the resultant lines to trim (you could try trimming the cone directly with the cylinders). Only slightly different from the “asbeastos” method…
My two cents,
That saddle shape looks hyperbolic: My 2 cents would be to make it via trimmed Degree 1 surface.
Hyperbolic.3dm (67.5 KB)