Thanks for the replies.
Stephen:
It is lines i mean by saying "spline shape" visually emerges. I have two pictures of the same point cloud just rotated. Sorry that its hard to see but without any illumination its hard to illustrate depth.
Chiro:
Thanks that says a lot, i have totally...
I am wondering if there is any way to create a model that can be used in a RANSAC method where a spline could be determined from a noisy 3d point cloud.
What i have is a volume containing a set of points in each xy-plane, having say 400 of these in the z direction and a spline shape emerges...