The ExtractIsocurve command creates curves that duplicate surface isoparametric curves at specified locations on the surface.


1. Select a surface.

The cursor is constrained to the surface, and isoparametric curves display at cursor.

The draft angle of the surface displays at the status bar.

2. Pick to create the curve(s).

Use the Int object snap for snapping to isoparametric curves intersections.

Command-line options

Direction (Surfaces only)

Specify the u, v, or both directions.


Extracts all isocurves in u, v, or both directions depending on the Direction option.

Toggle (Surfaces only)

Toggles the direction between u and v.


Determines whether surface trims are ignored or taken into consideration. When the marker misses the untrimmed surface, the no‑access cursor is shown.

No access cursor.


The ExtractIsocurve command creates the simplest possible curve exactly on the surface in u, v or both directions.
The ExtractIsocurve command is useful for creating trimming curves on surfaces. You can make surfaces trimmed along isoparametric curves into untrimmed surfaces with ShrinkTrimmedSrf.
You can use isoparametric curves to recreate an existing surface with different parameterization. To do this, extract several isoparametric curves, and Loft a surface through them.
If you need to put angled cross sections along a surface, use the Section command instead of the ExtractIsocurve command. If you need curved cross sections, use the Project or Intersect commands.
The Knot object snap can be used to create isoparametric curves at exact knot locations.
In contrast to the InsertKnot command, the ExtractIsocurve command creates separate curves that are not attached to the surface.
If you need to place an object on a surface, use the ExtractIsocurve command to add visual cues or locations that can be snapped to on the surface area and help position the object. Using the ExtractIsocurve command does not change the surface in any way.

See also

Extract object sub-elements

Rhinoceros 5 © 2010-2015 Robert McNeel & Associates. 17-Sep-2015