Final answer:
The use of parallel lines to create different values in an artwork is called hatching, which, along with crosshatching, helps to show shading and three-dimensionality. Hatching is not to be confused with linear perspective, which also uses parallel lines but for different purposes, such as creating depth through vanishing points.
Step-by-step explanation:
The technique of using a series of parallel lines set close to one another to differentiate planes of value in a work is called hatching. Hatching involves drawing parallel lines to create areas of shade, with the density of lines determining the darkness of the shade. This technique can be further intensified through crosshatching, where a second set of lines is drawn across the first, creating even darker regions. Such methods are used in media like etching, where only lines can be produced to represent different values.
Additionally, hatching helps to provide a sense of three-dimensionality and form to objects by representing shadows and shading. For instance, hatching can make the shadowed side of an object, such as a hat, appear more realistic and voluminous. Linear perspective, which uses a set of parallel lines that recede into the horizon to create an illusion of depth, is different from hatching but is also important in achieving three-dimensional representation on a flat surface. The lines in linear perspective, known as orthogonal, converge at the vanishing point and help to illustrate depth and dimensionality.