Forms, Shapes, Edges and Values
The most important skill or awareness required to create realistic images by drawing or painting is to understand the difference and relationship between Forms, Shapes, Edges and Values.
Forms are three dimensional, solid things while shapes are two dimensional flat things. A shape is bounded by edges.
An edge is the boundary where the value changes between two or more shapes. If the color transition across an edge is abrupt, the edge is said to be hard. If the transition is gradual (a gradient) the edge is said to be soft. Frequently, an edge transition is so gradual that the shape is not easily distinguished. Being able to make a distinction as to where an edge exists is relative to an artist’s individual perception, or the style of a drawing or painting. Edges are also the source of lines, however, the concept of a line (as in a line drawing) is actually a useful abstraction created in the mind of an artist and recreated in the eye of a viewer.
Value is the lightness or darkness of a shape; all of a shape is usually a single value. If two adjoining shapes are of the same value, they are, visually speaking, one shape. Value is one property of color, the other properties are hue and saturation.