This tutorial will show you how to create a cell shaded character in Adobe Illustrator, this is a fast technique utilizing the Live Paint bucket for block coloring, the gradient tool to add depth and form, and masked blended shapes for texture.
We will begin with the outlines already made. For more on this topic you can check out the tutorial, "Illustrator CS5 Variable Width Stroke Tool: Gestural Sketches and Digital Inking!" Once you have drawn your outlines open the Swatch panel and select the colours you will be using to fill the character. Chose a range of shades with a few contrasting colors for the highlights and shadows.
Depending how you made the outlines you may need to flatten the artwork. If so select the lines and choose Object > Outline Stroke. With the outlines selected click Live Paint Bucket (K) to make a Live Paint group, then simply click into areas with the appropriate colour to fill them.
Expand the Live Paint Group by selecting the artwork and clicking the expand button at the top of the workspace, then ungroup the paths (Command + Shift + G). Select part of the outline, then go to Select > Same > Fill colour to select every part of the outline (providing it's all the same color) and use the Pathfinder panel to Unite the outline for easy selection.
Make a background layer under the current layer. With the Rectangle tool (M) make a rectangle shape and fill it with a background gradient color. Draw two circles to mark out the reference points for the light sources.
On your drawing select a filled area, click the Draw Inside option at the bottom of the tool panel. Use the Blob brush (Shift B) and draw the highlights. You can see in the example below, the areas I have added correspond to the markers I placed in the previous step.
Once the highlight areas have been completed, draw the shadow areas using the same method you used to draw the highlights.
The "Draw Inside" function will turn your shapes into clipped areas, to modify the highlights and shadows, double click the main shape, this will isolate the contents, then use the Direct Selection Tool (A) and the Warp (Shift R) and the eraser (Shift E) Tools to tweak them to your liking.
Use the Gradient tool (G) to fill the highlight areas with linear and radial gradients.
Modify gradient stops as needed, if you want to blend the gradient with the color underneath, use the opacity controls for the gradient stops.
Add a new layer above the artwork for secondary shadows and highlights, these will be more subtle than the previous ones and will form the shape of your object or character.
To blend the colors, use screen blending mode for the highlights and multiply or overlay for the shading. Experiment with transparencies and gradient fills as well. For flare highlights draw a white blob or circle and add a blur effect. You can access the blend modes and blur settings from the Appearance Panel.
Add a texture layer between the artwork and the highlight. Place a pattern or texture over the artwork (File > Place), learn more about bitmap textures with the tutorial "Keep the File Size Down and Spice-up our Vectors with Bitmap Textures" in this example I have used a couple of dot screen patterns.
Add a texture layer between the artwork and the highlight. Place (File > Place) a pattern or texture on the new layer, in this example I have used a couple of dot screen patterns. Copy a shape from the artwork layer to use as a clipping mask. Lock the artwork layer, select the texture layer and paste the shape above the textures (Command F). Select the textures and the mask object and create a clipping mask (Command 7). Experiment with transparencies and blending modes to get the desired effect. I have used the Overlay mode.
There you go, a totally vector cell shaded character. For more tips on using the Blob Brush, Swatch Panel and Live Paint bucket check out my other tutorials. I hope you enjoyed this tut.