To Specify Boundary Blend Control Points
You can optionally define boundary blend control points after you define references for the blended surface.
1. Click > 
Boundary Blend. The Boundary Blend tab opens.
Boundary Blend. The Boundary Blend tab opens.2. Click the Control Points tab.
3. Right-click the Sets collector and click Add. The default control point set is valid for the first direction.
 | When you start specifying blend control points, the first boundary in the first direction is highlighted by default. |
4. Select a vertex or datum point from the first boundary. Points on the current chain that are valid for control point selection are highlighted in red. Select a matching blend control point. To skip one curve, right-click and select Next Chain in the shortcut menu to leave the control point for a curve undefined and skip to the next curve. After one set of blend control points is defined, they appear in Sets as Set 1. You can select New Set from the Sets column of the Control Points table to add a new set of control points.
5. To specify blend control points in the second direction, click Second and continue in a similar manner.
6. Optionally, you can select one of the following predefined control options from the Fit list:
◦ Natural—Blends using the general blending routine and resets the parameters for input curves using the same routine to obtain the best approximation for the surface.
◦ Arclength—Minimal adjustments are made to the original curves. Blends curves using the general blending routine, except curves are divided into equal pieces and blended piece-by-piece.
◦ Point to Point—Blends point-by-point. Point 1 in the first curve is connected to point 1 in the second curve and so forth. This option is only available for spline curves with an equal number of spline points.
◦ Piece to piece—Blends piece-by-piece. Curve chains or composite curves are connected. This option is only available for curves with an equal number of pieces.
◦ Developable—If two tangent curves in one direction are selected, you can toggle to determine whether you want the developable option.
7. Click 
OK.
OK.