450 Interiors Copyright Goodheart-Willcox Co., Inc. Learning to use certain drawing systems teaches you how to think spatially in three dimensions—a critical skill for interior designers. This skill helps a designer to visu- alize what a space will look like prior to construction and envision what issues might arise if not designed properly. There are three major types of projection systems: orthographic, paraline, and perspective. You can develop each type of drawing using a straight-edge, such as a ruler, or by using a sketching technique. Each drawing system has different strengths in communicating the inte- rior or space to the client and designer. Choosing which Drawing Systems The way to represent a three-dimensional reality on a two-dimensional surface has been a struggle for design- ers for many years. This struggle led to the development of drawing systems—or methods of projection. According to renown architectural graphics author, Francis Ching, a projection is “…the technique of representing a three- dimensional object by extending all its points by straight lines, called projectors, to a picture plane, an imaginary transparent plane.” This plane is the plane of projection. Designer: Kia Weatherspoon/Firm: Carlyn & Company Figure 13-24 Many designers create conceptual hand sketches and then digitally revise them by adding shading, shadowing, and lighting effects with such digital tools as SketchUp.