When a mesh point is chosen, you can select a color from the color panel/swatches/eyedropper tool to determine the color for that point.

Once you are done with defining the mesh points, you can move to the direct selection tool and choose each mesh point to alter its place and its direction handles.

You will also observe that as you append mesh points to an object, the paths joining the mesh points complement the contours of the object. Each click with the mesh tool appends mesh points to the grid object.

Choose the mesh tool from the toolbar, and click wherever you want within your vector path.

You can always append or delete mesh points later.

Selecting the number of rows and columns defines the amount of mesh points in your grid. If your original object has a color already registered to it, you can utilize the highlight and appearance alternatives to shadow the object with white. This will open the create gradient mesh dialog box, providing you with the capability to define the number of rows and columns in your grid.

Select Object > Create Gradient Mesh from the menu bar.

3d illustrator tutorial