We will show you each step to be taken in shading a cube in this tutorial, for this solid is a representative of all prisms, and, indirectly, of the cylinder. Place the cube on a sheet of light brown paper, and pin against the wall behind it a similar sheet to serve for background. Let the light fall from the right and from above the cube. The top face will be the brightest of those seen, and the darkest will necessarily be that next the cast-shadow.
How To Add Shadows to a 3D Cube (Shading Cubes) Step by Step Drawing Tutorial
Draw the cube carefully (reference this cube drawing tutorial here)and lightly in charcoal. Incorrect lines may be removed by dusting with the tinder. Do not draw with black-lead, as it is greasy, and will afterwards appear white in your shading.
Learn how to see the whites, grays, and blacks in your drawings so you can form 3-dimensional objects. Drawing the light and shadows in forms and objects is a hard thing to learn, but hopefully this tutorial will give you some methods and techniques to use in your future drawings.