Menu : SURFACE

Command: Deform:Twist

Shortcut : None

This command twists a target surface around an axis in proportion to its distance form a neutral line. The part of the surface on the centerline will not be affected whereas more remote parts of the surface will be twisted by an increasing amount.

After executing the command a parameter box appears requesting the axis direction for the twist. This direction is a centerline around which the surface will be twisted.

A second parameter box appears asking for the maximum angular twist and where the neutral line is to be positioned. There are three options for this at the fixpoint or at either extreme of the surface in the twist axis.

The accuracy of the twisting depends on the definition of the surface. The command automaticaly determines if a the resulting surface will be accurate and refines the surface if necessary.

All trim curves and textures applied to the surface will be discarded during twisting.

It is possible to twist B-spline and Bézier surfaces though to ensure smooth surfaces are generated it is better to bend B-spline surfaces.

The illustrations below show an initial hexagonal cylinder and the three possible results. In each case the twist axis is Z and the twist angle was 60 degrees. The first result is for the fixpoint option (the fixpoint was at the origin). The other two are for the +Z and –Z options. To understand the differences notice the position of the ‘notch’ in the cylinder. In the first case this has not moved at the center of the cylinder. In the second case it has not moved at the top of the cylinder. In the third case it has not moved at the bottom of the cylinder.