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er_pradip1-Visitor
1-Visitor
January 18, 2006
Question

CLASS OF SURFACES

  • January 18, 2006
  • 3 replies
  • 897 views
Hi,
Many a times i have heard guys talking about Class of surfaces
but when i approached them they could only tell me very little
about it (i.e G1,G2 ).
Kindly see if you can help me to get a beter understanding
about it, in detail.

Thanks in advance
Pradip

    3 replies

    U
    unknown11-Visitor
    1-Visitor
    January 18, 2006
    Isn't Wikipedia a wonderful thing?

    http://en.wikipedia.org/wiki/Freeform_surface_modelling

    To quote:

    The continuity is defined using the terms

    * G0 - position (touching)
    * G1 - tangent (angle)
    * G2 - curvature (radius)
    * G3 - acceleration (rate of change of curvature)

    Caleb Coburn
    Mechanical Engineer
    Roche Diagnostics


    S
    sp_481111-Visitor
    1-Visitor
    January 18, 2006
    Just to add to what has been said before, the surface connections are sometimes defined in terms of G (G1, G2 .. ) or C (C1, C2 ..)

    With G only the directions of the vectos need to match, ie for G1, the tangent vectors between the two surface patches will point in the same direction. For C1, both the direction and value of the vectors need to be the same.
    For the naked eye, it is difficult to make out the difference between the G and C continuities.

    If you are from around Detroit, you will also hear about Class A or Class B surfacing. Class A , used on Outer Body panels, is Curvature countinious and Class B is just Tangent countinious. I still havent figured out whether it refers to G or C countinuity !!!!.

    Bottom line is, in shaded mode, if you cant figure out where one surface ends and the other one starts, that is Curvature countinuity, if you see a sheen line (think of a radiused edge) it is tangent.

    Hope that helps

    Suresh Pillai
    First Technology Safety Systems


    B
    brianadkins1-Visitor
    1-Visitor
    January 18, 2006
    http://www.cs.berkeley.edu/~sequin/SPLINES/SplineLect1.html

    http://www.cs.berkeley.edu/%7Esequin/CS184/IMGS/Continuity.JPG
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