About Creating a Curvilinear Distance Constraint

While creating a curvilinear distance constraint, you need to give four parameters as inputs: two points, a curve and a distance value.

Consider the following while selecting points:

• An input point can be shared by several curves, control point of a spline, construction point, center of circle, etc.
• An input point can belong or not to the input curve.
• When no coincidence exists between the input point and the input curve, an implicit coincidence is created to force the point to be on the curve.
• The constraint is deleted if one of input points is deleted.
• The location of both the points on the curve is influenced by their order of selection.
• The position of the second point can be swapped around the first point when editing the constraint.

Consider the following while selecting a curve:

• An input curve can be a line, circle, ellipse, spline, concatenated curve, use-edge curve, etc.
• When a curve is periodic (circle, ellipse, closed curve) or is a line, instead of the relimited curve, the support of curve (periodic curve) is used to compute the curvilinear distance constraint. Otherwise constraint is inconsistent if one of input points is defined out of limits of parametric space of curve.
• The constraint is deleted if the input curve is deleted.

Consider the following while giving the input value:

• The value of curvilinear distance constraint can be positive or negative based on the selection order of the points and the orientation of the curve support.
• When the two points are selected in the direction of the support curve, the value is positive.
• The value is always positive at the time of creation of the periodic curves. You can change it to a negative value while editing the constraint.
• In the case of an ellipse or a circle to obtain the shortest distance, the first and the second point must be selected in the counterclockwise direction. For other periodic curve, the selection must be made by following the direction of the curve.
• The direction of the curvilinear distance measurement is always counterclockwise, and depends on the sequence in which the points are selected. This direction can be changed.
• When editing a constraint, you can:
  • Add a formula, tolerance, multiples values, or ranges
  • Edit a parameter or a comment
  • Change the step
  • Use the previous value, measure an item or between
  • Lock a parameter
  • Change the direction in which the curvilinear distance between the two points is measured.

An inconsistent constraint is created if one of input points is defined out of limits of parametric space of curve.

The curve’s support is used to compute the curvilinear distance constraint, which means that points may be on the support, but out of limits of the curve.

In case of a spline, the constraint is inconsistent if the curve’s support cannot be extrapolated.

In case of an arc, the support is a circle wherein both the points of curvilinear distance constraint can be defined out of limit points of arc. Constraint created is valid in this case.