Form is achieved by integrating depth or volume to the equation of shape. It is a three-dimensional element of design that encloses volume. It has height, width, and depth. For example, a two-dimensional triangle is defined as a shape; however, a three-dimensional pyramid is defined as a form. Cubes, spheres, ellipses, pyramids, cones, and cylinders are all examples of geometric forms.
Form is always composed of multiple surfaces and edges. It is a volume or empty space created by other fundamental design elements—points, lines, and shapes.
Types of Forms
Forms can be real or illusory. Real, three-dimensional form contains actual volume or physical weight while illusory, two-dimensional form is perceptual. Real forms are three-dimensional such as objects, sculpture, architecture, and packaging. Illusory forms are illusions of three-dimensional shapes in two-dimensional spaces and can be realized three-dimensionally by using several graphic conventions to achieve illusory results.
Representing several surfaces or planes of a two-dimensional form all at once is one way to visually represent a three-dimensional form without it receding in space or in scale. The most common types of projections are as follows:
An isometric projection is the easiest of projection methods where three visible surfaces of a form have equal emphasis. All axes are simultaneously rotated away from the picture plane and kept at the same angle of projection (30 degrees from the picture plane), all lines are equally foreshortened, and the angles between lines are always 120 degrees.
Axonometric (or Plan Oblique)
An axonometric, or plan oblique, projection is a parallel projection of a form viewed from a skewed direction to reveal more than one of its sides in the same picture plane. In isometric and axonometric projections, all vertical lines remain vertical and all parallel lines remain parallel.
Three-dimensional space and depth can also be achieved when one surface of a form is overlapped and partially obscured by another form. One- and two-point perspective drawings exemplify creation of a form's spatial depth with two-dimensional shapes overlapping on a two-dimensional picture plane.
Tone and Shading
Form can also be visually indicated through tone, shade, and texture. The surfaces of a form curving or facing away from a directed light source appear darker than surfaces facing a directed light source. This effect suggests the rounding of a two-dimensional shape into a three-dimensional form.