These parameters are shown in the comments of the example below. Disks can be made by setting the orientation to a zero vector. Cones can either be capped, as above, or uncapped. The above example is shown below Cylinder A cylinder is defined by 4 vectors, in a similar way to the cone primitive. The origin is the center of the base of the cone, the major and minor axis define the base, the orientation defines the extrusion of the base.
Cylinders can bave none, either, or both ends capped.
It is a shame that this description does not provide the ability to specify different radii at each end of the cylinder. Presumably a zero vector for the orientation would result in a two sided disk. Disk Beside the cone which can be used to define a disk, there is a specific disk primitive defined by 3 vectors. Just as the Triangle is redundant given a Polygon so the Disk would seem unnecessary. The data size savings are minimal, any internal optimisation can still be performed by detecting Cones and Cylinders that are essentially disks due to zero vector orientations.