Reparameterization

The Effect->Reparameterization command in the Model module allows you to change the parameterization of an existing NURBS curve or surface.

For more details on parameterization and its effects, see the Parameterization section of the Modelling User's Guide.

You cannot reparameterize a trimmed NURBS Surface. If you wish to do so:

• Delete the trim curves from the surface using Draw->Delete Trim Curves. If you have deleted the original curve used to trim, you may extract the trim curve before deleting (using Draw->Extract) and reuse it for projection.
• Reparameterize the NURBS surface.
• Trim the NURBS surface again.

Procedure

1. Select the NURBS curve or surface.
2. Choose the Effect->Reparameterization command.
   
   The Reparameterization dialogue box is displayed, in which you can select a new parameterization setting.
   
   The values displayed are not indicative of the current parameterization of your selection. Instead, it displays either the default setting Non-Uniform or the last setting chosen, if the dialogue box has been opened previously.
   
   
3. Select a parameterization option and click Ok to accept the settings, or click Cancel to exit the dialogue box.

Non-Uniform

The parameterization is not recomputed when you change the geometry of the curve (by moving, adding, or deleting points).

Chord Length

The delta between successive knots is related to the actual length of the curve segment, which in turn is approximated to the distance between control points.

The parameterization is completely recomputed when you change the curve geometry.

Centripetal

The delta between successive knots is related to the square root of the length of the curve segment. This tends to make smoother curves (in some cases), but usually distorts texture mapping on surfaces.

The parameterization is completely recomputed when you change the curve geometry.

Uniform

The delta between successive control points is expressed in equal increments of 1, without regard to the actual length of the curve segment.

It is useful to maintain uniform parameterization for skinning, as described on Surface->Skin.

Last updated 02-apr-1998