Why we shade

Shading is definitely where your artistic skills will be visible more
so than lining and coloring. In reality nothing is a solid color.
This is because there is always light in the real atmosphere. I
recommend that you take some art classes and if possible a 3D
modeling class. 3D modeling software is mathematically correct
and can help you to grasp different lighting effects from different
light sources on multiple geometric shapes and figures. Photography
is also a very helpful medium to assist the artist in learning
about light sources. A digital camera is a great way to learn
about light and will let you experiment with shapes and light’s
effect with shadows.