Mixture of curves and straight lines using the Curvature tool

How to Use the Curvature Tool for Straight Lines and Curves in Adobe Illustrator

The Curvature tool naturally wants to create curves. That is rather the point of its existence. If you click once around a sharp, zigzaggy object such as a crown, Illustrator happily joins the points with smooth bends instead of crisp peaks.

The result is not really a crown. It is more of a wobbly comb situation.

Fortunately, the fix is wonderfully simple:

• Double-click to make a corner point and straight line segments.

• Single-click to make a smooth curve point.

With this one little rule, the Curvature tool becomes much more useful. You are no longer limited to soft, organic shapes. You can build paths that move between sharp corners and smooth curves as you draw.

Set Up Your Path Before Drawing

When tracing an outline, a fill can make the path look confusing while it is still open. You may get odd filled areas appearing as you add points, which makes it much harder to judge whether the line itself is accurate.

For this kind of drawing, turn the fill off and work with a stroke only. Choose a stroke colour that stands out clearly from the reference artwork, then zoom in close enough to see the edges you are tracing.

If the first attempt goes a bit pear-shaped, select the path with the black Selection tool and delete it. Starting again is often faster than wrestling with a very early-stage path.

Drawing a Straight Crown with the Curvature Tool

A crown is a great first exercise because its outline is almost entirely corners. Start at one corner, then work your way around the shape by double-clicking every point where the direction changes sharply.

Keep double-clicking at every corner until you return to the point where the path began. There is one slightly weird detail when closing the shape: after making your final corner, click the original starting point once to close the path. If you double-click the starting point, Illustrator may turn it into a curve instead.

Do not worry if you forget. Mistakes here are completely fixable.

How to Correct a Point You Clicked Wrong

Suppose you single-clicked where there should have been a corner. You have two easy options:

• Undo the last point, then double-click to remake it as a corner.

• Double-click the existing anchor point to toggle it between a corner and a curve.

That second option is a particularly handy safety net. A curve can become a corner, and a corner can become a curve, simply by double-clicking the point with the Curvature tool.

Why Use the Curvature Tool for Straight Lines at All?

You could draw a crown with the Line Segment tool. You could create the eye panel of a character with a rectangle. You could make round eyes with the Ellipse tool. In normal day-to-day Illustrator work, those are often the sensible options.

But real illustrations rarely consist of only straight lines or only curves. A character outline might have sharp arms, a curved head, a straight base, and rounded facial features all in the same drawing.

That is where the Curvature tool gets properly awesome. It lets you keep building a single path while changing the character of each point as needed.

Mixing Straight Segments and Curves to Draw a Ninja

The ninja outline is a much more realistic Curvature tool exercise because it includes both kinds of shape. The arms have obvious angular corners. The hood and body have smooth curved sections. The trick is to look at the outline piece by piece rather than trying to label the whole object as “curvy” or “straight.”

Start at an obvious corner, such as the edge of an arm. Double-click it. Continue along straight sections by double-clicking each corner. When the contour begins to round, place a single click at the apex, which is the furthest point of the curve.

Then, as soon as that curve meets a straight edge, double-click the transition point to create a corner again.

Place Curve Points at the Apex

When working around a rounded section, do not scatter points everywhere. Find the part of the curve that sticks out the most and single-click there. The Curvature tool uses those points to pull the line into a smooth shape.

This can feel a little strange at first. You click a point, move the cursor away, and the shape may briefly look as though it has gone wrong. Keep building the next point or two. Often the curve settles into exactly the right place once Illustrator has more information about where the path is going.

There is no secret shortcut to instantly knowing the perfect anchor-point placement. You get better by drawing lots of shapes. After doing it many times, you begin to recognise where the curve needs to peak and where it needs to turn into a corner.

Handle Tricky Curve-to-Straight Transitions

Some parts of a drawing are neither obviously a curve nor obviously a corner until you look closely. A body contour, for example, may curve outward and then suddenly run into a straight arm or base edge.

Break that area into two decisions:

1. Click once at the apex of the rounded section.

2. Double-click where the straight segment begins.

That point where the curve ends may be subtle, but it is still a corner if the next section heads off in a straight direction. Trust the process. Sometimes the shape looks a bit suspect halfway through, then comes back to life once the following points are added.

Use Four Curve Points for Circular Shapes

For circular details, such as the ninja’s eyes, the Curvature tool usually produces a better result when you place curve points around the shape in its main quadrants. Think of a circle as having points at the top, right, bottom, and left.

This gives Illustrator enough information to create a balanced curve. It is a useful general habit for rounded shapes, even if the Ellipse tool would be quicker for a perfect circle.

Edit Anchor Points Instead of Starting Over

A wonky path does not mean the drawing has failed. It usually means one of three things:

• A corner should really be a curve.

• A curve should really be a corner.

• An anchor point is simply in the wrong position.

First, select the path with the black Selection tool. Then choose the Curvature tool to add, remove, or convert points.

Add and Delete Points with the Curvature Tool

If there are too many points on the path, click the unwanted anchor point and press Delete. Removing unnecessary points can make a shape smoother and easier to control.

If the path needs another point, click directly on the line where it is missing. A single click adds a curve point. If that new point is not far enough out to form the curve you need, move it into position.

A curve needs direction and space to travel. If a point sits directly on a straight segment, it cannot create much of a visible bend. Move the anchor point outward so Illustrator has a proper trajectory to work with.

Convert a Curve into a Corner

To turn a smooth point into a sharp corner, double-click it with the Curvature tool. This is ideal for the angular spikes and arm edges of the ninja.

You can also use the white Direct Selection tool for more detailed editing. Select the individual anchor point, then adjust it directly. This gives you very tight control when a point is close but not quite sitting on the intended outline.

A Useful Curvature Tool Shortcut

The Curvature tool has a slightly unusual keyboard shortcut: Shift plus the apostrophe key. The exact key position can vary between keyboard layouts, so check Illustrator’s displayed shortcut if it does not work as expected.

It is worth learning because the tool becomes far more useful once you can switch to it quickly while editing paths.

Do Not Stress About a Wonky Ninja

Everybody struggles with the Curvature tool at the beginning. The important thing is not getting every path perfect on the first attempt. It is learning to identify the difference between a corner point, a curve point, and an anchor point that simply needs moving.

Keep practising with simple outlines. Draw sharp crowns. Draw rounded circles. Then draw things that mix both, such as a ninja with angular arms and a curving hood. Each attempt makes the next one less mysterious.

FAQs

What is the difference between single-clicking and double-clicking with the Curvature tool?

A single click creates a smooth curve point. A double click creates a corner point, which produces straight segments between corners.

How do I change a Curvature tool point from a curve to a corner?

Select the path, choose the Curvature tool, and double-click the anchor point. This toggles the point between a curve and a corner.

Why does my path fill with colour while I am drawing?

The selected appearance includes a fill. Turn the fill to None and use a stroke while tracing an open outline, so the developing path is easier to see.

How do I add or remove anchor points with the Curvature tool?

Click a path segment to add a point. To remove an existing point, select it with the Curvature tool and press Delete.