If the shape of the highlight isn’t exactly what you want, you can move mesh points with the white arrow and even drag their curve handles to reshape the mesh lines attached to them, and thus the direction and depth of their colour transitions. Remember, mesh points behave just like anchor points; the only difference is that they also contain colour data instead of just curve direction and depth data. You can even use the Convert Anchor Point tool on mesh points to change them from smooth to corner points or manipulate the curvature of mesh lines on either side independently.

The initial highlight. There are curve handles
on the mesh points.

If you need more mesh points, switch to the Mesh tool, which is located on the Tools panel between the Column Graph and Gradient tools. When you click with the Mesh tool in a mesh patch, the empty space between rows and columns, you’ll create a new row and column. Clicking the Mesh tool directly on a mesh line, however, will create a row or column—clicking on a vertical mesh line creates a new row at that point, clicking on a horizontal mesh line creates a new column. If you add a new row or column to an area that has already been colored, the resulting mesh points will pick up the colors at the point of insertion.

If you need fewer mesh points, perhaps because colors are transitioning too sharply, hold down the option key and click with the Mesh tool on a mesh point. That will delete the column and row intersecting at that mesh point.

Note that you can also assign color to the mesh points at the outside of your path shape, at the ends of column and row lines. This is how I gave my tomato the backlighting on its right edge.

For larger areas of color, the shadow on the front of my tomato for instance, click with the white arrow (not the Mesh tool) inside a mesh patch. That will automatically select, and enable you to color simultaneously, all four mesh points that define the shape of that patch.

Colour four mesh points at a time by clicking
within the mesh patch rather than on a specific
mesh point.

Continue colouring until you’re happy with the result. If you make a mistake, use Command-Z to undo, or just recolour the mesh point; they’re always editable, even after saving, closing, and re-opening the Illustrator document.

When the tomato is done, you can finish it off with leaves and maybe a stem, each of which can also be colored via a gradient mesh.

Believe it or not, the tomato I used for this example took me only 15 minutes to create from start to finish—including drawing the initial paths and adding and colouring the leaves and stem. Initially, your artwork might take longer; but with a little practice, you can quickly create stunningly coloured gradient mesh objects.

The finished tomato, complete with gradient mesh leaves and stem, and a standard radial gradient cast shadow.

In part two of this tutorial, which runs on Monday, I'll outline some easy keyboard shortcuts you can use to accomplish the tasks above.