Hello
Attached is code for a button that creates a multipatch sphere and adds it as a feature to a multipatch layer (rename the attached file to MultipatchSphere.cs). it uses the MultipatchBuilderEx builder object constructing patches of type TriangleStrip.
Let me know if you have any questions about the code.
As a result of your question, we have added additional constructors to the MultipatchBuilderEx object (and the related convenience methods) to support the creation of some basic 3d shapes. These will include cubes, tetrahedrons, diamonds, hexagons, cylinders, spheres, sphere frames and cones and will be available in the 2.9 ArcGIS Pro release..
Regards
Narelle