Creating depth and volume in realistic nature paintings is near and dear to me. I often see people struggling with getting their art to look 3 dimensional on a 2 dimensional surface. When I worked at the New York Botanical Garden’s Illustration Certification program I designed a class called, “Light on Form”. I designed the class to break down a step by step progression to understand the surface contour of a many different shapes and how light and shadow effects the surface contour when it is coming from an upper left positioning at 45 degrees from the picture plane. Here is a video that introduces this concept using a two-toned speckled bird egg and graphite. I hope that you enjoy the how-to tutorial. If you have any questions or would like to leave feed back I would be happy to answer your questions. Enjoy!