Curves-on-surface

Curves-on-surface are special curves that are primarily used to define the regions on a NURBS surface for trimming. Curves-on-surface reside in the UV space of a surface, rather than in the XYZ space of the scene.

You can create curves-on-surface by:

• Projecting an existing XYZ world space curve onto a surface.
• Intersecting existing surfaces together. The curve-on-surface is created along the region of intersection.
• Drawing directly on the surface. Click the magnet icon on the toolbar to make a surface “live”, then use the curve creation tools to draw a curve-on-surface directly on the surface.
  

For a region to trim successfully, the curve-on-surface must fully enclose a region on the surface to be trimmed, or bisect the surface to be trimmed.

Curves-on-surface are primarily used to trim surfaces, and can also be used as an edge for new surfaces.

Curves on surface (along with their edit points) have a special Move manipulator. When you move a curve on surface, the manipulator constrains the curve on surface to the surface and allows movement across the surface in U and V.