Creating Cusps

When you modify an anchor point to create a point of discontinuity in a path, you create a cusp. A cusp can be created as you draw a path, or when you modify an existing path.

You can create two types of cusps:

• A type1 cusp is an anchor point with only one direction line.

• A type2 cusp is an anchor point with two non-collinear (independent) direction lines.

Creating a Type1 Cusp
A type1 cusp is an anchor point with only one direction line. A type1 cusp can occur when:

• A straight segment is connected to a curved segment

• A curved segment is connected to a straight segment

• Two curved segments are connected 

Step 1
Select the Pen tool from the tool palette.

Step 2
Move the pointer onto the page and click.

Step 3
Move the pointer, then click again to create a straight segment.

Step 4
Position the pointer on the anchor point you just created, hold down the Option key and drag out a direction line.

Step 5
To create a curved segment with one direction line, move the pointer and click to create another anchor point.

Step 6
Position the pointer on the last anchor point you created, then drag out a direction line.

Step 7
Move the pointer, then drag to create another anchor point with direction lines.

Step 8
Option-click the anchor point you just created to collapse the right direction line.

Step 9
Move the pointer, then click to create a straight segment. Another type1 cusp is created.

Creating a Type1 Cusp on an Existing Path

Step 1
Select the Arrow tool, then click anywhere on a path.

Step 2
Click an anchor point on a curved segment to select it.

Step 3
Option-double-click one of the direction points to collapse a direction line and create a type1 cusp.

Step 4
To pull out the direction line you collapsed, Option-drag away from the anchor point (creating a type2 cusp)

• To make both direction lines collinear, Option-Shift-click one of the direction points. (If you drag, the movement of the direction lines is constrained to 45-degree increments.)

Step 5
When you’re finished making changes, click away from the path to deselect it.

Creating a Type2 Cusp
A type2 cusp is an anchor point with two independent direction lines.

Step 1
Select the Pen tool from the tool palette.

Step 2
Move the pointer onto the graph document and drag.

Step 3
Create another anchor point and drag out direction lines.

Step 4
Position the pointer on the anchor point you just created.

Step 5
Option-drag to create an independent direction line.

Creating a Type2 Cusp on an Existing Path

Step 1 
Select the Arrow tool, then click anywhere on a path.

Step 2
Click an anchor point on a curved segment to select it.

Step 3
Option-drag a direction point around its anchor point using an arc motion to create a type2 cusp.

• If you Option-drag, then hold down the Shift key as you continue to drag, the direction line movement is constrained to 45-degree increments.

• To make both direction lines collinear, Option-Shift-click one of the direction points.

Step 4
When you’re finished making changes, click away from the path to deselect it.

End of Topic