rhino fairing

Discussion in 'Software' started by jollyricard, Mar 12, 2011.

  1. jollyricard
    Joined: Jul 2009
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    jollyricard Junior Member

    i using rhino, i want fairing the curves; my question is:
    in every stations must i modify control point for remove curve reverse ?
     
  2. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Depends on how smooth a curve you want or need. But first look at how many control points you have and decide if you really that many for the shape of curve you are want?

    Rebuild let's you pick the number of points to use for the rebuilt curve. You can check the deviation using Preview and then Calculate options in the pop-up menu.

    FitCrv is another way to rebuild the curve within a specified tolerance but it can add rather than reduce the number of points if the tolerance is set small.
     
  3. jollyricard
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    jollyricard Junior Member

    ok, thanks;
    i use rebuild command; then i use curvatureGraphOn command and some curves show a curve reverse; What should I do?
     
  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Two alternatives:

    1) Move the relevant control points to make the surface as you want it.

    2) Use Fair. The only control you have is the selection of the tolerance parameter. Start with a small value. If it's not smooth enough then repeat Fair or try again with a larger tolerance. Fair changes the original and doesn't keep a copy, so if you need the original then copy it before using Fair.

    Where did the curves come from? Did you create them in Rhino, import them from other software, or are they from fitting curves to the dimensions in a table of offsets?
     
  5. jollyricard
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    jollyricard Junior Member

    i create curves in rhino with points cloud;
    i used fair but in some stations the graph line (curvatureGraphOn) crosses the curve;
    must i control that no curve passes through the x-z plane?
     
  6. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    I assume the curves will be used to model a surface, and the point cloud is made from a physical surface.

    The curvature graph line crossing the surface means that the curvature is reversing. If the curvature is reversing but the curve is on the surface then you may not need to eliminate the crossings.

    It is difficult to avoid crossings using points from a point cloud because the points are not aligned along smooth curves. You may need a different tool than Rhino to create curves from point clouds.
     
  7. jollyricard
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    jollyricard Junior Member

    ok, thanks;what kind of different tool do i use?
     
  8. bhnautika
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    bhnautika Senior Member

    jollyricad if you could post some pictures of the surface in question it may help to pick the right tools and advice for the job.
     
  9. DCockey
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    DCockey Senior Member

    I have very little experience with extracting points to create curves from a cloud of data.

    bhnautika's suggestion to post some pictures is very good. It would help us understand what you are trying to accomplish.

    A page from McNeel, the developers of Rhino, about reverse engineering from a cloud of points: http://wiki.mcneel.com/rhino/reverseengineering

    A page which lists several plug-ins for Rhino to help to go from a point cloud to a model: http://www.rhino3d.com/resources/default.asp?category=13
     

  10. jollyricard
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    jollyricard Junior Member

    many thanks;
     
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