.. hehe .. I remember doing something similar once!
.. of course for my purposes I only needed two colors, Black and White; and my sources were all still Images .. so it was possible to cheat by using the Threshold
Effect in Adobe Photoshop or The GIMP to get the effect ^_^
(would YOU want to draw in all those Lines to delineate where the Shadows should fall yourself?? .. no thank you sir!)
.. whether such a simple approach will work in your case as well .. depends on the Shading of your Source Images of course ..