Combining shapes curvature & shape builder tools into Fox shadows

Combining the Curvature and Shape Builder Tools in Illustrator: Add Moonlight and Shadows

Key takeaways

• Combine simple shapes, curved paths and Shape Builder into one practical drawing workflow.

• Create shadow regions without drawing every shadow as a separate closed shape.

• Use HSB brightness to make darker versions of your existing colours.

• Avoid accidentally editing underlying objects with the Curvature tool.

• Clean up spare paths and merge regions again when a shadow does not work.

A sleeping fox, a moon and a few shadows. Not a huge project, right? But it is a really useful way to start combining Illustrator tools rather than practising each one in isolation.

I call this skill stacking. Simple shapes give us the starting artwork, the Curvature tool draws the boundaries, and Shape Builder turns those boundaries into regions we can colour. That is much closer to how drawing in Illustrator actually works.

1. Start with your sleeping fox

Open the sleeping fox illustration you have already drawn. If you are working with the exercise files and need a fresh starting point, open Catchup01 instead.

The starting scene has an orange fox, outlined stars, a dark background and a pale ground rectangle. We will add a shaded moon, experiment with shadows on the fox, and create a large diagonal shadow across the ground.

As you work, keep these controls handy:

• V: switch to the Selection tool, also known as the black arrow.

• Shift-click: add another object to the selection.

• Shift + M: switch to Shape Builder.

• Option on Mac or Alt on PC: subtract with Shape Builder.

• Escape: stop drawing the current path.

For the moon and the fox details, select only the shapes you need. Locking the background is a sensible precaution against accidentally including it. Later, when we make the ground shadow, we will deliberately select the ground rectangle.

2. Build a shaded moon from a circle and a curve

Start with the simplest part: draw a circle for the moon. Give it a white fill and no stroke, and position it in the upper-left area of the scene.

Now we need a curved boundary between the bright part of the moon and its shaded side. We do not need to draw a complete shadow shape by hand.

1. Choose the Curvature tool.

2. Draw a curve across the circle, letting the path extend beyond its edges.

3. Use single clicks to create curved points.

4. Press Escape, or switch to the Selection tool, to finish drawing without closing the path.

If the path seems to be attached to your cursor, that is simply Illustrator waiting for the next point. Escape disconnects it. The black arrow does the job too.

You can temporarily give the path a fill or a visible stroke to make it easier to understand. Its appearance is not the important part, though. We are using it as a boundary for Shape Builder.

Colour the region, then remove the leftovers

1. With the Selection tool, click the circle.

2. Hold Shift and click the curved path so both are selected.

3. Switch to Shape Builder using Shift + M.

4. Choose a darker grey fill and click the moon region you want to shade.

5. Hold Option on Mac or Alt on PC, then click or drag through the unwanted path segments outside the moon.

There we go: a little shaded moon. Shape Builder is not just for trimming or joining shapes. It can also colour the regions created by intersecting paths.

3. Draw a shadow boundary across the fox’s head

Next, try a shadow across the lower part of the fox’s head. This gives us a chance to mix curves and straight sections in the same path.

Choose the Curvature tool and click once for a curved point, then once again for another curved point. Where you want a corner and a straight section, double-click.

That single-click versus double-click distinction is worth practising. It lets you build a path that curves around part of the head, then runs straight out beyond it.

When the Curvature tool grabs the wrong object

Here is one of the quirks you may run into when combining tools: click too close to an existing edge and the Curvature tool can pick up the shape underneath rather than continue the new path you intended.

If that happens, undo. Then extend your dividing path past the edge of the shape instead of trying to land exactly on it. We will remove the extra bits afterwards, so there is no need to be precise about where the path ends.

For this head boundary, a black stroke with no fill makes the path easy to see. Press Escape when you have finished drawing it.

Turn the boundary into a separate region

1. Select the dividing path with the black arrow.

2. Hold Shift and select the head shape.

3. Switch to Shape Builder.

4. Choose an orange from your fox swatches and click the intended shadow region.

5. Hold Option or Alt and remove the spare dividing-path segments.

6. Return to the Selection tool, deselect everything, then select the new region on its own.

Now that part of the head is its own chunk. We can change its colour independently without changing the rest of the head.

4. Use HSB to make a darker version of a colour

You could choose another orange swatch for every shadow. I prefer to start with the original colour and make it darker. That is where HSB in the Color Mixer is really handy.

Your colour controls may initially show RGB or CMYK, depending on how the document was created. Those modes have their uses, but HSB is much more straightforward for this particular adjustment.

• Hue: changes the colour itself, such as shifting orange towards another colour.

• Saturation: changes how intense or washed out the colour is.

• Brightness: changes how light or dark the colour is.

Select the new shadow region and restore the original orange if you have been experimenting. Switch the Color Mixer to HSB, then lower Brightness slightly.

That gives you a darker orange without having to juggle individual RGB or CMYK values. It is a little colour-editing trick I use all the time.

The head shadow may look a bit like a beard at this stage. That is fine for an experiment. We will come back to it once the rest of the scene is finished.

5. Repeat the workflow for straight and curved shadows

Once you have made one shadow, the rest follows the same pattern: draw a boundary, select it with the underlying shape, fill the region, and clean up.

Create a straight dividing line

For a straight shadow boundary, use the Curvature tool and double-click at each end. Press Escape to stop drawing, then select the line and the fox shape together.

You do not have to change the line to a black stroke every time. A straight path with no visible stroke may be impossible to see when deselected, but Shape Builder can still recognise the selected path.

The visible stroke is a drawing aid, not a requirement. If an invisible boundary makes things confusing, give it a temporary stroke. Otherwise, leave it as it is.

Use Shape Builder to fill the new region with the original colour, then reduce its HSB brightness. Alternatively, choose an already darker swatch if it suits the illustration.

Add a curved shadow along the back

For the fox’s back, mix single-click curved points with double-click corner points. Draw the boundary across the body, then press V to return to the black arrow.

Select the body and the new path together, press Shift + M, and fill the shadow region with a slightly darker orange.

Sometimes a spare segment remains after the Shape Builder operation. If it is an independent leftover object, select it and press Delete. You do not have to perform every bit of cleanup with Shape Builder.

6. Use a duplicate shape to shade the tail

Why redraw a curve if you already have a shape with the curve you need? For the tail, we can use a copy of the existing tail shape as our dividing object.

1. Select the tail shape and copy and paste it.

2. Make the duplicate a little larger.

3. Position it over the original tail so their edges create the shadow region you want.

4. Give the duplicate no fill and a black stroke if that helps you see the overlap.

5. Shift-click to select both tail shapes.

6. Use Shape Builder to fill the intended region with a darker version of the tail’s orange.

7. Hold Option or Alt and remove the unwanted parts of the duplicate.

This is the same basic idea as the earlier shadows, just with an overlapping shape instead of a newly drawn path.

Depending on the appearance of the original objects, you may end up with an unwanted stroke or an extra object sitting on top. Switch to the black arrow and check what remains. Remove the stroke if it belongs to the finished shape, or delete the extra object if you do not need it.

7. Cast a large shadow across the ground

Now for the big shadow extending away from the fox. We only need a straight dividing line across the ground rectangle.

The Line tool could do this, but the Curvature tool gives us another chance to practise double-clicking for straight sections.

Deselect before starting a new path

If the ground rectangle is still selected, clicking its edge with the Curvature tool can add a point to that rectangle instead of starting a separate line.

That behaviour is useful when you actually want to edit an existing shape. The Curvature tool can also add points to an ellipse and reshape it. It is just not what we need here.

Undo any accidental edit, then deselect everything before starting the shadow boundary. Begin well away from existing edges so Illustrator does not pick them up.

1. With nothing selected, choose the Curvature tool.

2. Draw a diagonal boundary that crosses the ground rectangle and extends beyond it, visually beginning near the fox.

3. Double-click to create straight sections.

4. If you need more space, hold the spacebar and drag to pan the canvas.

5. Press Escape to finish the path.

6. Select the path and ground rectangle together.

7. Switch to Shape Builder and fill the shadow side with a slightly darker version of the ground colour.

8. Remove the surplus path with Option or Alt, or select it afterwards and delete it.

The fox now has a large shadow running diagonally away from it. It is a simple treatment, but it helps tie the moon and the character into the same scene.

8. Finish the scene and undo a shadow that does not work

For the stars, select them together and change their appearance to white fill with no stroke. That feels cleaner here than the original orange outlines.

Then take another look at the head shadow. Mine looks less like moonlight and more like the fox has acquired a five o’clock shadow. Not quite the plan!

The useful thing is that we can join those regions back together:

1. Use the Selection tool to select one head region.

2. Hold Shift and select the other.

3. Press Shift + M for Shape Builder.

4. Drag across both regions to merge them into one shape again.

We broke it apart, tried something, and put it back together. That is a useful skill in its own right.

The point is not to keep every shadow you create. It is to get comfortable moving between tools and making decisions as you draw.

Try the workflow on your own fox: use a curve for one boundary, a straight path for another, and a duplicate shape for a third. Draw, divide, colour, clean up, then reassess. That is skill stacking in practice.

Key terms

Skill stacking

Combining several familiar tools into one workflow. Here, simple shapes, the Curvature tool and Shape Builder work together to create shading.

Curvature tool

A tool for drawing and editing paths with curved points and corners. In this workflow, single clicks create curved points and double-clicks create corner points for straight sections.

Shape Builder

A tool for working with regions formed by selected, intersecting objects. You can fill individual regions, merge them by dragging across them, or subtract unwanted parts with Option or Alt.

HSB

Hue, Saturation and Brightness. Lowering brightness provides a straightforward way to create a darker version of an existing colour.

Fill and stroke

A fill colours the interior of a shape, while a stroke gives its path a visible outline. A temporary stroke can make a dividing path easier to see while you work.

FAQs

Do I need to close the Curvature path before using Shape Builder?

No. For these dividing boundaries, leave the path open and extend it across the target shape. Press Escape, then select the path and the shape together before using Shape Builder.

Why does the Curvature tool edit the shape underneath?

The Curvature tool can edit existing paths as well as draw new ones. Deselect existing objects before starting a new path, and avoid beginning or ending too close to their edges.

Does a dividing path need a visible stroke?

No. Shape Builder can recognise a selected dividing path without a visible stroke. A black stroke simply makes the path easier to see while drawing and selecting it.

How do I remove leftover lines after creating a shadow?

With Shape Builder active, hold Option on Mac or Alt on PC and click or drag through the unwanted segments. You can also use the Selection tool to select independent leftover objects and press Delete.

Can I merge a shadow region back into the original shape?

Yes. Select both adjoining regions, activate Shape Builder with Shift + M, and drag across them to combine them into one shape again.