To Create a Datum Curve through Points
This procedure creates a datum curve that passes through existing points as a spline or as a sequence of alternating tangent lines and arcs.
1. Click > , click the arrow next to 
Curve, and then click Curve through Points. The Curve through Points tab opens.
Curve, and then click Curve through Points. The Curve through Points tab opens. | You can also select points to define the curve first, and then open the Curve through Points tab. |
2. To select points to define the curve, click the Placement tab, and perform these actions:
a. To add the first point to the curve definition, click the Point collector, and in the graphics window, select an existing point, vertex, or curve end.
b. To add additional points to the curve definition, click Add Point, click the Point collector, and in the graphics window, select a point, vertex, or curve end.
3. To connect a point to the previously added point, select the point in the points list, and select an option:
◦ Spline—Constructs a curve using a three-dimensional spline that passes through the selected datum points and vertices.
◦ Straight line—Constructs a curve through the datum points using a straight line.
▪ Add fillet check box—Adds a fillet to round the curve at the selected point.
▪ Type a fillet radius value in the Radius box.
▪ Group with equal radius points check box—Makes the point part of a logical group of points that have the same radius.
4. To define conditions at the ends of the curve, click the Ends Condition tab, and perform these actions:
a. Under Curve side, select either the Start Point or End Point of the curve. The settings for that end are displayed.
b. Next to End condition, select an option:
▪ Free—Makes the curve free of any tangency constraint at this end.
▪ Tangent—Makes the curve tangent to a selected reference at this end. Click the Tangent to collector, and select an axis, edge, curve, plane, or surface to which the curve end is tangent.
▪ Flip—Changes the tangent direction to the other side of the reference.
▪ Make end curve to be perpendicular check box—Makes the curve end perpendicular to a selected reference when the selected tangency reference is a surface or plane. Click the Perpendicular to collector, and select an edge.
▪ Curvature continuous—Makes the curve tangent to a selected reference at this end, and applies a continuous curvature condition to the point. Click the Curvature continuous to collector, and select as axis, edge, curve, plane, or surface to which the curve end is tangent.
▪ Flip—Changes the tangent direction to the other side of the reference.
▪ Make end curve to be perpendicular check box—Makes the curve end perpendicular to a selected reference when the selected tangency reference is a surface or plane. Click the Perpendicular to collector, and select an edge.
▪ Normal—Makes the curve normal to a selected reference at this end. Click the Normal to collector, and select an axis, edge, curve, plane, or surface to which the curve end is normal.
5. If you create a datum curve through two points, you can tweak the curve in 3D space and dynamically update its shape.
a. Click the Options tab, select the Tweak curve check box, and click Tweak Curve Settings. The Modify Curve dialog box opens.
b. Modify the curve.
6. Click 
.
.For more information, refer to the Part Modeling Help.