Technical drawings, according to Tooley and Dingle, authors of the book "Btec National Engineering: Core Units for All Btec National Engineering Pathways," are "graphical representations of an idea or product that is to be processed, manufactured or constructed." These drawings (also known as drafts) are often implemented by designers, architects and engineers to accurately describe an object. Today, Computer Aided Design (CAD) is often used to expedite this process, though the basics or technical drawing are still an important aspect of design.
The practice of spatial visualisation allows you to represent a three-dimensional object as a two-dimensional drawing and taking the information given in a two-dimensional drawing and forming a mental picture of what that drawing would look like as a three-dimensional object. Goetsch, author of "Technical Drawing," points out that, while some inherently possess the talent of spatial visualisation, many do not; however, those who are not naturally proficient can learn with practice.
Orthographic drawings are two-dimensional representations of an object drawn in series to create multiple fragmentary views of an object. According to Mitton, author of "Interior Design Visual Presentation," it is helpful to visualise these projections as a transparent box: the "plan" is the view from the top of this transparent box, showing only elements that are visible when looking directly down at the object. "Elevations" are represented by the views from the sides of the box, showing the visible object in a picture plane. When the building or object is drawn as a vertical plane sliced through it, this view is called a "section;" similarly, a horizontal plane that has sliced through the building or object reveals a "floor plan" view. Dobson of forum4.info says that orthographic drawings include general arrangements, drawings, developments and sections that show internal features.
Pictorial drawings, or three-dimensional drawings, can range from freehand sketches to detailed, precise perspective illustrations, according to Mitton. These drawings can be useful in presenting designs to clients and allowing designers to see the entire volume of space. One form of pictorial drawings is a paraline drawing. Ching, in his book "Architectural Graphics," describes that these drawings comprise axonometric projections (isometric, dimetric and trimetric projections) and obliques. These drawings all have three common characteristics, says Mitton: parallel lines are drawn as parallel, with no converging or vanishing points; vertical lines are drawn as true verticals; and some method of proportional scale is used. Conversely, perspective drawings (also pictorial drawings) depict a three-dimensional object as it might be viewed from a window, complete with vanishing and converging lines.
- Forum 4: Drawing Techniques
- "Btec National Engineering: Core Units for All Btec National Engineering Pathways"; Mike Tooley, Lloyd Dingle; 2007
- "Interior Design Visual Presentation: A Guide to Graphics, Models, and Presentation Techniques"; Maureen Mitton; 2003
- "Technical Drawing"; David L. Goetsch; 2005
- "Architectural Graphics"; Francis D. Ching; 2009