Fairing curve : curvature and torsion controll

With the Position and Normal constraints tools, the user can indicates a few key points to the system, in order to build the model. With the Position and Normal discontinuity tools, the user can lighter the smoothness of the surface along specific curve. With the fairing curve, the user will be able to adjust in a fine way how the smoothness is computed.
The fairing curve is only one type of curve, where two different values can be adjusted to controll two different effects.

• The curvature control value adjust the curvature all along a curve : each 2D-segment of the piece-wise linear curve – drawn in the left window, 2D view – tends to become a straight line in the 3D model in the right window.
• The torsion control value tends to propagate the local orientation of the surface all along the curve. Associated with a position discontinuity, this tool is very useful to create silhouettes.

These 2 images show the efficiency of the curvature control value. Along the blue curve, the linear curvature has been removed, and the blue curve has become a straight line.

The next animation shows the most spectacular effect of the torsion control value. A circle shaped fairing curve has been drawn on the grid, and only one normal constraint has been drawn on one point of the fairing curve. The torsion control value propagates the local orientation of the surface - in the direction orthogonal to the curve.

Fairing curve are created, modified and removed in the same way as the Position or Normal discontinuities

To adjust the parameters of the fairing curve, right-click on one of the points to open the information dialog box

• Old version : modify only the first two values - curvature and torsion. 1000 is an average value to get a reasonable result. A value greater than 20000 will overconstraint the system and is not recommanded. A value below 10 will have no effect.
• New Version : adjust the two sliders to modify the strength of each effect.