The B-Spline tool

The B-Spline tool lets you build B-spline paths by placing a series of nodes that indicates the direction the path should follow. Each node on a B-spline path can be a curve or corner control node. To create a B-spline path:

  1. Select the B-Spline tool  in the Toolbox.
  2. Click anywhere in the workspace to set the starting point of the path.
  3. Move the pointer and watch the thin gray line as you move the cursor to see how this curve segment will look when you click. Hold down the SHIFT key to constrain the position of the node relative to the previous node. By default, the constraint is 45- or 90-degrees. (The actual angle is determined by the Rotation steps setting in the Units and Grids panel of the Options dialog box .)
  4. Click to place another node. You can hold down the ALT key while you click to place a sharp corner at this point.
  5. Repeat steps 3 and 4 until you're ready to end the path. Note that you can remove the last node you added by pressing the DELETE or Backspace key.
  6. To end the path (stop drawing), do one of the following:
    • To create a closed path, position the cursor on top of the first node (the starting point) and click.
    • Double-click at any point to place an ending node.
    • Press ENTER or ESC to end the path at the last-placed node.

Appending paths

When the Drawing tools append to path option is enabled in the Stroke panel of the Options dialog box, you can easily extend an already-existing path with the B-Spline tool by placing the cursor over the beginning or ending point of the line and then drawing. Or, you can draw a new path with the B-Spline tool and end by clicking on one of the open nodes of a path. In this case, the new path will be joined with the old one.

Tip: In general, think about adding two nodes for each curve along your path. So, while you can create a triangular shape with rounded corners with just three nodes, you will find you have more control over editing that shape if you create three pairs of nodes (six nodes total). Placing nodes to form angles of around 120 degrees offers a reasonable balance between the number of nodes and shape control.

The path on the left was drawn with only three nodes. The path on the right was drawn with six nodes (three pairs).

Tip: When you want to create a curve coming out of a straight portion, add an extra node before the curve begins. Otherwise, the curve will affect the straight-line segment.

By placing a node between a straight segment and a curve segment, you maintain the straight segment.