# Spline3D

The Spline3D panel allows you to add and edit three dimensional spline data.

## Create 3D Splines

A 3D spline entity can be used to capture non-linear characteristics of a force, bushing, or motion. While a curve entity can be used to define a non-linear behavior that varies about a single independent variable, a 3D spline can be used to define non-linear behavior that varies about two independent variables. An example of such an application is the combustion force acting on the piston of a reciprocating engine. The combustion pressure, and thereby the force, is dependent on the angle of rotation of the crank and also on the speed of the crank.

## Edit 3D Splines

A 3D spline consists of a x-vector (or column) and more than one y-vector. Each y-vector is defined on a certain z-plane.

### Define the Properties of 3D Splines

From the Properties tab, you can define the spline data.

### Define the Attributes of 3D Splines

The Attributes tab can be used to define the scale and offset for the X and Y vectors and the Z values. When a data vector is scaled, the vector is multiplied by a specified value. The original data values are not actually altered, however. Offsetting a data vector shifts the data along the corresponding axis.

You can also enter math expressions in the Scale and Offset fields.

### User-Defined Properties for a 3D Spline

If desired, define the 3D spline using the User-Defined tab, which will allow you to specify the properties of the spline using user subroutines.