the illusion of light and 3D form for a CUBE. There are 6 essential values needed to create the illusion of a 3d cube. the first three are the foundation or base values: 1. Light 2. Shadow 3. Cast Shadow. Your accent values are: 1. Hi-light 2. Core Shadow 3. Cast shadow. When creating quick idea drawings you limit the number of values you use to suit your dead line. It is important to prioritize your use of the value scale. Remember you are the artist and it falls on you to choose. The order from lightest to darkest : 1. HI-LIGHT 2. LIGHT. 3. SHADOW. 4. REFLECTED LIGHT. 5. CORE SHADOW. 6. CAST SHADOW.