These five modeling factors are quite efficient at representing forms, and are a good base for realistic paintings:
- Shadow (or Tone)- This area is all parts of the form that are parallel to the direction of the light source or further. It also includes cast shadows.
- Light - The area of the form generally facing the light.
- Halftone - Between the tone and light. While the light and shadow together establish the overall mass of the object, the halftone is critical for defining the more precise shape of the object.
- Highlight - A specular reflection of the light source. This differs from the light in that it usually will not appear where the form is facing the light, but rather in the spot where the light source would show if the form were a mirror.
- Depth (or Accent) - These are areas where very little light is reaching. Particularly when the light is from above, there will be small pockets where very little light reaches. Generally they are found in the shadow areas, but do also occur in the light where two forms or subforms overlap each other dramatically. For example, underneath the edge of a cloth laying on a table you will usually find a dark line- this is a depth. They're also often found where the feet touch the ground, where necklines and cuffs of clothing overlap the figure, and in crevices like the armpit and the crotch. Depths are quite valuable for showing one form sitting on top of another.
To create a very convincing representation of form and surface more modeling factors might be needed. In such a case, it can be useful to divide the light, halftone, and shadow areas into smaller and more specific modeling factors. For example:
- Light Light
- Middle Light
- Dark Light
- Light Halftone
- Middle Halftone
- Dark Halftone
- Terminator (the division between the halftone and shadow)
- Dark Dark
- Medium Dark
- Light Dark