Maxsurf Curvature question

[ErikG]

Hi ppl I'm fiddling w. Maxsurf and have come across a bug or an issue...

When checking the curvature on something (a waterline) i sometimes get instantaneous jumps in the curvature eventhough i have a smooth enough curve with only medium flexibility. How can that be, there are no knuckles on that curve and the jump might not be that big, but it IS a jump.
Either there is a bug or I'm missing something.

I can't decide what I think of the program... It is just SO much slicker and more userfriendly than Pro Surf, but somehow I do get the feeling that there are some issues in the program that I can't put my finger on. on the otherhand it has a great suite of programs that covers almost anything you'd ever need.

Any thoughts or opinions?

I'm going to d/l more demos now

Erik

[BrettM]

It could be an issue to do with the surface resoultion. Try setting the "Precision" to a higher level.

I use maxsurf and recommend it to everybody.

[ErikG]

That might do it, I didn't think about that. Thanks.

I also realized that it did dissapear when I changed the "flexibility of the batten", don't remember what it was called in the program.

Erik

[Andrew Mason]

The discontinuity in the curvature plot means that you are using low stiffness surfaces, probably order 3. An order 3 curve is effectively made up of short segments of curve that are joined with slope continuity (1st derivative) but not curvature continuity (i.e. its 2nd derivative), as a result you will see steps in the curvature plot. An order 4 curve is continuous in its second derivative (curvature), but not its 3rd derivative, so although you wont see steps in the curvature plot you will see kinks.

As you keep increasing the order of the surface it will become continuous at higher and higher derivatives, making it progressively smoother. Maxsurf has now been modified to allow surfaces up to order 10 to be used.

The downside of the greater fairness afforded by the stiffer surfaces is a loss of local control over the surface - it becomes harder to create local features such as bumps and hollows. Selection of the correct order is usually a compromise between the level of fairness required and the need to create areas of locally high curvature.

[ErikG]

Thank you very much for your answer.

Erik