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Once a NURBS surface is selected (use the Pick button of the Edit NURBS Surface window), you can edit its control points intereactively interactively (see NURBS surface). Select the control points as if they were regular points and enter their new positions in the usual way (see Point definition).
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- Insert knot: You are asked for a knot value between 0.0 and 1.0 and it is then inserted. The program checks that the knot multiplicity is not greater than the order. This option can be used to have more points defining the same surface.
- knot removal: the inverse of knot insertion. Remove knots if possible without change shape with a given tolerance. (interesting to save memory)
- Elevate degree: With this option the degree of the surface is raised by one. The new surface will have the same shape but with more control points and knots.
- Reduce degree : the inverse of degree elevation. Decrease the polynomial degree if possible without change shape with a given tolerance.
- Change Weight: A new positive weight can be introduced for any control point, with the exception of the end points that must have weight=1 (to force the surface to pass over the corner control points).
- Cancel weights: This converts the weights of all the control points to 1.0
- Reparametrize: This reparameterizes reparametrizes the surface obtaining an optimized surface. When a Nurbs surface is not well parameterized, the mesh is of a lower quality.
- Similar cubic: This option converts the surface to a simplified one with degree=3 in both parametric directions, which is only an approximation of the original one.
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