Verifying developable surfaces

Rhino Rhino for Windows
3

Another way to check if a surface is developable (assuming the surface is degree 1 with two control points in one direction).

  1. Create a ruling line:
    ExtractIsocurve command in the degree 1 direction at the desired location.

  2. Create lines normal to the surface at either end of the isoline, or two other locations along the isoline:.
    Line command with Normal option. End OSnap makes it easy to select the ends of the isoline.

  3. Check for twist along the isoline:
    Angle command with the two normal lines created in the previous step.
    If the angle between the two lines is 0 then there is no twist along the isoline, and the surface is developable along the isoline.

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