Using Bézier Handles, in Practice

The example in the video above focuses on two points (a line), whereas most vector shapes have considerably more points. As such, there are often two Bézier handles extending from a point — one on each side. Here are some of the ways to create a curve around a vector point in Sketch:

“Mirrored” is the default and most common method of controlling a Bézier curve. This approach uses two handles that extend the same distance from the vector point, at the same angle. The handles seem to form a single line that is “tangent” to the curve. The Mirrored option is based on the fact that if both handles are at the same angle, the shape will have a completely smooth curve; in other words, there will be no visible corner/point along the shape as is the case with the Disconnected option.

“Asymmetric” is similar to Mirrored in that the handles are at the same angle, although the handles do not have to be the same distance from the vector point. This is especially useful when a curve needs to taper off more quickly on one side.

“Disconnected” allows you to change each handle independently of the other. There are two use cases for this:

You would like the shape to have a noticable angle/corner when it hits that vector point, rather than creating a smooth curve through the point. You may only want one handle; control over a curve on one side of the point, and no curve on the other side. If this second option is what you’re after, click on the handle control point you’d like to remove and press the “delete” key.

Straight Points & Rounded Corners:

When the Straight option is selected, a vector point has no handles or curve through it. If two vector points with this option are adjacent to each other, the path between them will be a straight line. Sketch gives you the option to round the corner of any Straight point (aka border radius). Although Sketch makes it appear incredibly easy to round any corner with a single point and radius value, under the hood the software is actually acheiving this by calculating Bézier curves for you. Pretty neat! If you want to reveal these Bézier curves, simply flatten your shape (described here).

Get Your Handles Under Control!

One of the most confusing things about Bézier curves is where to place handles and vector points in order to acheive your intended result. Designer and lettering artist Dave Coleman of the AGSC recently wrote a great article about this, and I’ll summarize a few of his main points.

If you strategically place vector points along a curve, you can substantially reduce the amount of points in the shape. The more simply your shapes are constructed, the easier they will be to change, and the smaller your filesizes will be. Dave recommends finding the “outermost point” along a curve , and placing your vector point there.

, and placing your vector point there. With your points in position, it’s time to fiddle with the handles. By aligning the Bézier handles vertically or horizontally , curves will often be smoother and faster to fine-tune. Because you only need to move the handle along one axis, the whole process of making curves becomes easier.

, curves will often be smoother and faster to fine-tune. Because you only need to move the handle along one axis, the whole process of making curves becomes easier. …Except, occasionally, when it doesn’t. Sometimes a curve can’t be fully reproduced unless Bézier handles are at an off-angle, or the vector point isn’t positioned at the outermost point. This is OK. Like all guidelines, follow them, understand them, and — when necessary — break them.

You may be relieved to know that there’s a quick way to snap Bézier handles to 90° angles: just hold down the “shift” key while dragging a handle control point. If, like in the graphic below, this feature isn’t behaving as expected, look to see if “rounding” is turned off. If instead you’re using “Round to full pixel edges” or “half pixel edges”, and the vector point is not at an exact pixel or half-pixel position, the handles will not snap to 90° angles.