Perspective drawings, isometric drawings, and oblique drawings are the three basic forms of pictorial drawings that are commonly used in architectural presentations.
In perspective drawings, the viewer's position is related to the subject through the use of lines called "perspective lines." These lines make it possible to see the scene from any angle without changing the overall size or appearance of objects in the picture. They also help to give an accurate representation of three-dimensional space on a two-dimensional surface. Perspective drawings are created using tools such as compasses, protractors, and ruler/template devices.
Isometric drawings show objects in a two-dimensional plane with no regard for their actual height or depth. Thus, isometric drawings can be useful in representing large subjects or complex arrangements of objects without obscuring details. They can also serve to illustrate how objects relate to one another when they cannot be shown in perspective. Isometric drawings are drawn using geometric shapes and simple photography techniques.
Oblique drawings show objects that are not parallel or perpendicular to the viewing screen. This type of drawing is useful in depicting scenes where only part of the subject is visible or in illustrating concepts in architecture that cannot be expressed in perspective.
Perspective drawing is classified into three types: one-point perspective, two-point perspective, and three-point perspective. In one-point perspective, objects closer to the viewer appear smaller than those farther away. In two-point perspective, all objects in view occupy equal distance from the viewer. In three-point perspective, objects closer to the viewer appear larger than those farther away.
One way to think about it is that in one-point perspective, everything is equally far away from you; therefore, if something is closer to you, it has to be smaller. In two-point perspective, whatever direction you look, things are in relative positions of equality distance from you; if something is closer to you, it must be smaller. In three-point perspective, whatever direction you look, things are in relative positions of size from you; if something is closer to you, it must be larger.
One advantage of using this method for teaching geometry to children is that they find it easier to understand. The disadvantage is that it can be difficult to draw in two-point or three-point perspective without looking like a fool!
Architectural drawings, structural drawings, civil drawings, mechanical drawings, electrical drawings, and so on are examples. Working drawings have traditionally been two-dimensional orthogonal projections of the structure or component being described, such as plans, sections, and elevations. In recent years, three-dimensional (3D) models have become popular in place of physical drawings for many applications because they can include information about size and orientation that a printed plan cannot convey.
With today's technology, it is possible to create digital drawings which contain both 2D and 3D elements. These are called mixed-mode drawings. They provide all the advantages of both traditional methods, which use only one form of drawing, and modern methods, which utilize multiple forms of drawings.
Mixed-mode drawings are useful when you need to display different aspects of the same object. For example, if you were designing a book cover with complex curved surfaces, you would use a mixed-mode drawing to show both the front and back views of the cover at the same time.
There are several types of mixed-mode drawings available for architects and designers. Here are two common ones: sfumato and photorealistic.
A sfumato drawing shows the shape of an object without specifying what material it is made of or how it is finished.