Fairing with Freeship

Discussion in 'Software' started by Swey, May 6, 2011.

  1. Swey
    Joined: Mar 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Pennsylvania, USA

    Swey Junior Member

    Is there anyway to do fairing with Freeship other than try to perceive a fair curve by eye. I put the image on my flat screen lcd tv to get the view as large as possible. I was wondering if this can be trusted as a method or are there hidden problems that would only be apparent until blown up to full size developable parts? Thanks for your thoughts.
     
  2. philSweet
    Joined: May 2008
    Posts: 2,337
    Likes: 199, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Yes, there is. You can import stuff from other places. you can set them as control curves (a poorly described feature in the manual I have, which is old.) Read the entire manual, and read the wiki on NURBs. An important feature of NURB surfaces is the concept of "locality". Moving a single control point only affects a limmited area and has absolutely zero affect beyond. This is different than most splining techniques. Figuring out how many control points you need to do the job and not using more than you need also aids in faring. So much for the general stuff. Fare what you got using the curvature function (bunch of pink lines).
     
  3. Swey
    Joined: Mar 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Pennsylvania, USA

    Swey Junior Member

    Thanks philSweet. What can be imported from other places?
     
  4. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    With Freeship's subdivision surfaces the locality of control points is not quite the same as with NURBS.

    The best tools of the trade in Freeship are zebra shading and gaussian curvature for rendering, and control curves for edges. You can change the rendering mode by right-clicking on the window and with control curves see the curvature of the edge. Add the control curve, select the pink line and check that control curves are shown.
     
  5. Swey
    Joined: Mar 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Pennsylvania, USA

    Swey Junior Member

    I am missing a step or something. The manual on page 31 shows little purple lines perpindicular to the controlcurve but I can't seem to find how to display them. I tried to highlight the sheer and then selected "Control curves" under Visibility and the sheer turns purple but how do I get the perpindicular purple lines to display?
     
  6. Swey
    Joined: Mar 2011
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Pennsylvania, USA

    Swey Junior Member

    I got it! I just kept monkeying with it untiil I got the little pink lines to come on. Thanks for your help. Is there anything written on interpreting zebra shading?
     
  7. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    Yes, you'll have to select the actual control curve and not the control net edge. Often this best hidden by hiding the control net.

    For Zebra-shading, just rotate the model and keep on eyeballing the shading as it flows.
     
  8. philSweet
    Joined: May 2008
    Posts: 2,337
    Likes: 199, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Thanks Liki. Read up a bit more. I think this is going fix troubles I've had getting tight radii at panel intersections to behave. Wrong concept of locality.

    Also might explain why I tend to get a tiny crease down the centerline of a deck when I think I've taken pains to get rid of it. Can't force a desired slope easily with subdivisions, and control curves sometimes lead to "Runge's phenomenon" or something like it.
     
    1 person likes this.
  9. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 247, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    So how did you do it? I've tried and re-tried, but I've never managed to visualize the curvature lines... :confused:
     
  10. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 247, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Ok, I've made it. It is done by first enabling "Visibility --> Curvature" option and then with "Calculations --> Intersections" command, by checking the station whose curvature is to be visualized.
     
  11. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    It's called elbow grease... :D
     
  12. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    That's the way for stations, buttocks, water lines and diagonals. But you can also add control curves into edges and show their curvature similarly. Select edge, add control curve, toggle curvature visible and select the added control curve.
    My version of Freeship shows curvature for intersections only in a way of which even I can be certain that it is incorrect. :/ I have just coined that feature as broken, but does it work for others? I think my version is Freeship+ 3.12 now.
     
  13. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    I'm still using 2.83 because the resistance calculations work better for me there. I have the newer one too, but cannot see the resistance calculations.

    On a curvature you can calculate the variations between points to get them precise.

    You can also right click, select mode, developability check. Then move the points to where you get a smooth colour.
     
  14. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 247, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    I agree that there must be something wrong with the curvature plot. The curves are showing irregularities which do not result in either zebra, gaussian or shaded mode. I hope VictorT is reading this... :/
     

  15. LP
    Joined: Jul 2005
    Posts: 1,411
    Likes: 57, Points: 58, Legacy Rep: 584
    Location: 26 36.9 N, 82 07.3 W

    LP Flying Boatman

    Emphasis added.



    No luck on searching the wiki on NURBS. Can you post the link?


    Is this what you were referencing?

    http://en.wikipedia.org/wiki/Non-uniform_rational_B-spline
     
    Last edited: May 9, 2011
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.