Maxsurf Curvature question

Discussion in 'Software' started by ErikG, Dec 29, 2002.

  1. ErikG
    Joined: Feb 2002
    Posts: 397
    Likes: 12, Points: 18, Legacy Rep: 344
    Location: Stockholm, Sweden

    ErikG Senior Member

    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 :D

    Erik
     

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  2. BrettM
    Joined: Apr 2002
    Posts: 204
    Likes: 1, Points: 0, Legacy Rep: 16
    Location: Australia

    BrettM Senior Member

    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.
     
  3. ErikG
    Joined: Feb 2002
    Posts: 397
    Likes: 12, Points: 18, Legacy Rep: 344
    Location: Stockholm, Sweden

    ErikG Senior Member

    Thanks Brett

    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
     
  4. Andrew Mason
    Joined: Mar 2003
    Posts: 397
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    Location: Perth, Western Australia

    Andrew Mason Senior Member

    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.
     

  5. ErikG
    Joined: Feb 2002
    Posts: 397
    Likes: 12, Points: 18, Legacy Rep: 344
    Location: Stockholm, Sweden

    ErikG Senior Member

    Thanks Andrew

    Thank you very much for your answer.

    Erik
     
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