Figuring out shadows

One of the tricky aspects of the lizard/skull painting is figuring out how the shadows would fall on the skull. I used my lizard models to replicate how shadows would fall inside of the cranium. I used a curved piece of white paper to simulate the curvature of the inner part of the skull, and shot reference photos. The lizard to the right has its tail coming over the front of the skull, so to figure out how that shadow would fall, I placed a clay "tail" over the front of my cast skull.