Modify how the length of the cylinder primitive is specified?

[CnlPepper]

At present the cylinder extends from z=0 to z=h where h is the length/height of the cylinder along it's axis. Consider whether it would be better to define the cylinder height from z0 to z1 so users can quickly define e.g. a cylinder that is centred on there axis. At present they need to translate the cylinder.

The cost of this will be additional maths + complexity.

This line of thought could apply to other primitives e.g. cone.