Spline Interpolated


This topic will explain the differences between the various spline types, and explain the options found in the spline functions. This topic will also give brief description of the Snap Increment function, will describe where to find the function, provide quick steps on how to use it, and provide links to related topics.

The Spline Interpolated Function

Splines are designed to produce a smooth curve between a set of selected points. Spline creation can be accomplished by selecting snap points or coordinates using the mouse position when the Sketch/Single Picking mode is used, or by selecting multiple entities at once with the Multi-Picking mode. When using the Multi-Picking method, other entities are selected for spline creation. In these cases, though, it is the end, or middle snap points that are actually used. In the image below, a chain of several different entities is used as an example.


Geometry used for selection


End Points


Middle Points




When creating a spline, whether points are selected individually, or whether multiple entities are selected at a time, the points that are used for the creation of the spline (shown above) are usually referred to as Knots. Once the spline has been created, you can still edit it by selecting it, and choosing Entity Modify. What appears at that point, are the control Points. Clicking on one of the control points will allow you to adjust its position manually and see the preview update in real time to see how the spline will be affected, should you confirm those changes.


Generated Spline (Blended)


Knots (Creation Points)


Control Points (Modification Points)




Snap Increment

This function support the use of the snap increment when selecting the location of the entities. The snap increment allows you to get precise results when using mouse selection and helps to reduce data entry modifications.


To learn more, view Snap Increment.

To open Interpolated:


  • In the Entity group of the Create 2D ribbon, click the down arrow under Spline, and select Interpolated.


The parameters display in the Data Entry Manager.


Note: Whether you click the main icon, or the down arrow to get to the other options, you will have access to the same options in the Data Entry Manager.

Spline Types

When the Spline function is open, many Spline Types are available to you. In the images below, you will see how each Spline Type reacts with a given set of points.













Points From Mode

These options will determine how the knots for the spline will be selected.


  • Sketch/Single Picking - With this method, knots will be selected one at a time, by clicking in empty space, or by hovering over an entity and selecting one of its snap points.

  • Multi-Picking - With this method, many knots can be selected at the same time, by window picking existing entities.




When the Multi-Picking method is used, and geometry has been selected, this group becomes available. By default, the end points of the selected entities are used as the knots for the spline. This group will allow you to change the result by forcing the spline to utilize the center snap points as the knots instead. See the images below for an example.


  • Use End Point - With this method, knots will be created from the snap points on the end of the selected entities.
  • Use Middle Point - With this method, knots will be created from the snap points in the middle of the selected entities.


Approximated / Use End Point


Interpolated/ Use End Point


Fit/ Use End Point


Blended/ Use End Point





Approximated / Use Middle Point


Interpolated/ Use Middle Point


Fit/ Use Middle Point


Blended/ Use Middle Point






Point List

The Point List displays all knots selected for the creation of the spline. This will allow you to select an entity and delete it from the list, or even alter its order in the spline creation when the Sketch /Single Picking mode is being used.


Point List


(Move Up) - Move the highlighted item up the list.

(Move Down) - Moves the highlighted item down the list.

(Delete) - removes the highlighted item from the list.

(Delete All)- removes all entities from the list.

This list box will show the entities currently selected for the function.


  • OK - finalizes the function.

  • Cancel - exits the function.

Quick Steps

  1. Select the InterpolatedSpline Type.

  2. Select a Points From Mode option.

  3. Select the knots for spline creation.

    1. If Multi-Picking is used with entities other than points, chose an Option.

  4. Modify the Point List as necessary.

  5. Click OK to finalize the spline.

Related Topics

The CAD Overview