Create Curve by Tangents

Use it!

Used to create a B-spline curve that passes through a set of points while maintaining user-defined tangent directions at those points. You can define points and tangent directions interactively using data points or by identifying elements. In the latter case, the curve passes through the starting points of the identified elements and uses directions of the elements as tangent inputs. The curve may be either quadratic or cubic.

Tool Setting	Effect
Input By	Sets the manner in which the input points are located. Enter Tangents — graphically define a series of vectors. Pick Elements — identify existing elements.
Curve Type	Sets the curve fitting algorithm: Cubic — cubic (order 4) Quadratic — quadratic (order 3)

To create a B-spline curve that passes through a set of data points with interactively specified tangent directions

1. Select the Create Curve by Tangents tool.


2. In the tool settings window, set Input By to Enter Tangents.


3. Enter a data point to define the curve's starting point.


4. Enter a data point to define the tangent direction at the defined starting point.


5. Enter a data point to define the next point through which the curve will pass.


6. Enter a data point to define the tangent direction at the point defined in the previous step.


7. For each additional point through which the curve will pass, repeat steps 5-6.


8. Reset to generate the curve.

   As data points are entered, defining each curve point (1) and tangent direction (2), graphics dynamically display the point(s) and the tangent direction(s). After placing the required data points, entering a reset generates the curve.

To create a B-spline curve that passes through the vertices of existing elements and whose tangent directions correspond to the elements' directions

1. Select the Create Curve by Tangents tool.


2. In the tool settings window, set Input By to Pick Elements.


3. Identify an element.


4. Identify another element(s).


5. Accept.
   The curve is generated. It passes through the endpoints of the identified elements, and its tangent directions correspond to the elements' directions.

   Identify the elements (1, 2, 3) from which the curve is to be generated. Accept (4) to generate a curve passing through the end points of the selected elements, with its tangent directions corresponding to the elements' directions.