Changing number of vertices on an object after creation.

Is there a way to change the number of vertices on a mesh long after creation?

For instance, a cylinder with 16 vertices changed into 24 vertices.

I know the f6 menu lets me choose the vertices count on creation, but what about long after?

It depends on your circumstances. One you have added your object you cannot go back to the F6 menu so you will have to manually change the geometry yourself.

If its just a cylinder just can just delete the original and add a new one with more sides with the same location/rotation.
You could subdivide edges and use the circle option in the loop tools addon to make it an even circle with the increased number of sides.

As I remember, maya can do this, but not blender.

Blender cannot since it is not a parametric modeler, so much as to say that object shapes are defined and placed in a modifier stack that can then later be changed.

Yes, but it depends a bit on the particular shape, and it only works with nurbs objects.

Use two bezier objects, and bevel the one with the other. Then each curve’s U resolution can be set individually, controlling the number of loops.

Be careful not to change the preview or render U unless you want to override the active spline’s manually set u.

See example below. I duplicated the column, and changed the u factor for both curves to control the number of loops. A nice side effect is that the number and distribution of the loops can be easily controlled by adding any control point in any given position along the curves, and by repositioning the points on the curves and/or dragging the handles for each point.

With the complex non-organic projects I work on, this is a very useful and convenient method of working, and completely non-destructive. Of course, this workflow does have some drawbacks and limitations: to add more surface detail at some point we will need to convert the objects to polygons. Texturing can be an issue as well. But at least we won’t have to commit until the very last moment.