Modeling with advanced techniques > 3D curves > Create a 3D spline curve
Create a 3D spline curve
The Create and Modify Spline commands of the 3D Curve menu provide a straightforward method to define open or closed spline curves by specifying a series of points in 3D space. As with 2D splines, these points are interpreted either as the interpolation points or the control points of the spline curve.
At any point in the operation you can choose whether to create an open spline curve, or whether the two ends should be joined to form a closed loop. To achieve fine control over the shape of the spline curve, you can attach a tangent vector at the current interpolation point.
As with other 3D curves, you can define a point in 3D space either by entering its coordinates in the user input line, or by catching to existing geometry. With 3D spline curves, however, you can also click the mouse directly in the viewport to specify a point, see Identify points when creating 3D curves.
By first defining points through which you want the spline curve to pass, you can provide target vertices or edges to which you can catch the spline curve.
As you create the spline curve, Creo Elements/Direct Modeling provides dynamic visual feedback so that you can immediately see the shape of the spline curve as it develops. If the spline curve adopts the wrong shape, you can step back through each selection until you return to a point at which the curve had the required shape and start over.
You will find that the 3D spline functions are so flexible that they can be used to complement many Creo Elements/Direct Modeling commands and functions. This is especially true in the freeform and surfacing areas, where they can provide alternative, and usually quicker, methods to perform certain tasks. For example, you can create a mesh for skinning operations without defining and positioning multiple workplanes.
The figure shows how a combination of 3D curve techniques have been combined to construct the mesh for a Skin operation. Both direct creation methods (straight lines and spline curves) and indirect creation methods (convert for the perimeter edge) have been used. The entire mesh was created without a workplane.
With Freeform commands you can also use 3D spline curves to create spine tracks along which you can sweep a profile to add cables or pipes to a model.
To create a 3D spline curve,
1. Click 3D Geometry and then, in the 3D Curve group, click Spline 3D. The Create Spline dialog box opens.
The Point 3D CoPilot is active. Use the CoPilot to specify the points of the curve.
2. Type a name for Part.
3. Choose a Mode: Interpolation or Control.
4. If working in Interpol mode, choose a start condition in the Start Cond box:
Position: Define the position of the curve by specifying points in the viewport.
Edge: Define the position and start condition of the curve in relation to an existing edge.
Face: Define the position and start condition of the curve in relation to an existing face.
If you select Edge or Face, use the Curve connect condition to specify various conditions for the curve.
5. Click point(s) in the viewport to specify the interpolation points.
6. To specify a tangent condition for a point, click Tangent then use the Vector 3D CoPilot to define the tangent vector at that point. You can specify tangent vectors for each interpolation point of the spline curve. Right-click and Accept the direction. Right-click and Clear to remove the tangent from an interpolation point.
7. Choose an End Condition:
Position: No special conditions are set.
Closed: Creates a closed periodic curve.
Edge: Define the position and end condition of the curve in relation to an existing edge.
Face: Define the position and end condition of the curve in relation to an existing face.
8. Click to complete the operation.
Other options in the Spline menu:
Back Point: Erase the last point created and move back.
Next Curve: Complete the current curve and create another curve.
Curvature Continuous: Specify the curvature continuous connect condition for the 3D curve. A curvature continuous condition will maintain the same tangent direction and the same curvature radius. For more information, see Tangential or curvature continuous condition.
Follow Me: The Point 3D CoPilot moves with each click in the viewport.
Feedback: Shows the curvature radius.