… for Apple Motion

Tip #1803: Why Use B-Spline Curves?

Larry Jordan – LarryJordan.com

B-spline curves are always curved and smooth.

I was reading several technical articles about when to use B-spline curves. While they make good points, here’s the key thing you need to know.

A B-spline is always a smooth curve. Unlike a Bezier curve, which can have corners or curves, B-splines are always smoothly curving from beginning to end.

This means that if you have problems drawing smooth curves, as I do, B-splines come to your rescue.

To draw one:

• Click the small arrow next to the Pen tool and choose B-spline.
• Then, start clicking in the Viewer. As you do, a curve is instantly created.
• Drag a red control point to change the shape of the curve. The shape will change, but it will ALWAYS be a smooth curve.
• Click the starting point to create a closed curve, otherwise, you’ll create an open curve by default.

EXTRA CREDIT

Open the HUD, assign the curve a width, then click the Shape Style icon at the bottom of the HUD to assign a style to the border. This image uses Traditional > Chalk Easy with the border set to a cyan color.

NOTE: For shape styles to appear, the border width needs to be enabled and greater than 0.

This concept is the same for B-spline masks: always a smooth curve.