UV scan works pretty well for this. It will drive the grid based on the isoparametric curves that define the surface so the grid will flow with the surface contour. Once you get your grid defined how you want it you can hit "to points" to turn it into a bunch of single point if that is your ultimate goal. The only problem with this tool is that it doesn't support analog scanning. Touch trigger only.
For me it depends on the size of the surface involved as well as the point density.
I have used the UV scan method and it works ok, but if you don't use it often, it takes a while to figure it out and lots of refining to get exactly what you want.
If it's just a single surface and one part (instead of a family of parts) I do it manually with a grid overlaid with the CAD graphics utilities.
I'm not at a PCD-capable machine right now, so I can't get this exact, but I'll give it a go.
On the toolbar is an icon that gets you to a window that allows you to create a 3-D grid.
I just set this to the density I want, say, .25" X .25" and then manually add autovector points at the grid intersections.
As I said, depending on the surface area, this can go pretty fast and is easily edited.
Think about it.
This can take only a few minutes, and instead of spending a bunch of time getting the scan "just right" you just point and click a bunch of points and yer done.
If you need the spacing exact you will need to use the scan method.
Grid scan will project a grid onto the surface with reference to the CAD position in graphics display, but will not follow the surface boundaries for an even distribution (like on a curved surface)
UV scan will create evenly spaced points for your defined grid, but only in a rectangular-shaped area, so if the CAD surface you are trying to populate with points is oddly shaped this method might not work too well.
Manually placing points with John's method above can be a good all-around option if these two won't give you the results you want.
There is also setting up datum points in the DESIGN SOFTWARE (solidworks, CatV, etc), and bringing them in via iges, step, etc. and selecting them with the auto-vector dialogue open.
Oh, and you can also use several BOUNDARY scans with increasing offsets from the boundary edge to create a grid-like array of hits.
Like DaSalo said in another thread, you can use a free form scan by reading a text file that contains points, or just reading file to measure points. It's easy on a plane, not on a curved surface without doing some maths...
I do it sometimes, the major problem is to have a math def of the surface, then derivate it to calculate the tangent, and extract the vector hit... Sometimes it's funny !
