Graphical projection systems encompass a wide range of methods for representing three-dimensional objects on a two-dimensional surface. These methods are fundamental to engineering drawings, as they provide the means to communicate complex shapes, dimensions, and spatial relationships in a clear and interpretable manner. Each method offers a different approach to visualizing an object, catering to various needs, from technical precision to visual realism.
The diversity of projection methods arises from the different ways in which lines of projection can be utilized to depict an object. Some methods aim to preserve the object’s proportions and true dimensions, while others focus on providing a more realistic portrayal by mimicking how the human eye perceives depth and distance. Depending on the method used, the resulting drawings can serve different purposes, from detailed technical guides to conceptual visualizations.
In perspective projection, all projection lines converge at a single point, called the station point or center of projection. This setup mimics how the human eye perceives the world: objects appear smaller as they get farther away, and parallel edges (like railroad tracks) seem to converge in the distance. Perspective projection produces a realistic, three-dimensional appearance and is commonly used in architectural renderings, illustrations, and visualizations where visual realism is important. However, because it distorts size and angles depending on depth, it is not used for technical measurements.
In parallel projection, the projection lines remain parallel to each other as they extend from the object to the viewing plane. This method does not attempt to imitate human vision but instead preserves the true scale and shape of the object’s features along certain axes. Parallel projection is further divided into orthographic and axonometric types. Orthographic views show each face of the object in true shape (like front, top, and side views), while axonometric views—such as isometric or dimetric—show a rotated view to give a sense of 3D without introducing perspective distortion.
