If a curve is specialized and not a NURBS, you are asked to confirm whether you want to convert it into a NURBS (unless you have deselected the Ask before converting check box).
| Tolerance for converting into NURBS
You can control the way the curve is converted by setting a suitable Tolerance value. The lower the tolerance value, the more accurate the resulting NURBS will be and, hence, the more control points it will have. |
| The scale factor Tangency modifies the section of the curves near the point where they meet. The scale factor controls the amount by which that section of each curve is modified. It must be a value greater than 0. The higher the value, the more marked the change in the section of the curves. In technical terms ... The scale factor controls the distance between the first control point of the curves, i.e., the one that is in contact with the other curve, and the second control point. Increasing the scale factor means moving the second control point away from the first and hence modifying the shape of the section of the curves nearest the common point. |
| The propagation factors The propagation factor controls the extent to which the change is distributed along the curve. It must be a value between 0 and 1. If you set 0, propagation is inhibited and the change remains local. For values greater than 0 (the maximum is 1), the higher the value the more the change extends to the rest of the curve. |
| The Weights Each curve can be associated with a numeric value - its weight - which indicates how much the curve is to be modified relative to the other. The higher the weight, the less the curve changes. If the weight of a curve is zero, the other curve is not modified at all. The weight of a curve is a value between 0 and 1. |
The Tangent angle box shows the tangent angle value in the common point.
or 
to confirm your selections and modify the curves.Click
to discard your changes.