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For many years architects and engineers have utilized a system known as orthographic projection to accurately represent three-dimensional objects graphically on paper. In recent years the term "multiview

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Figure 5.1A An example of a simple drawing of objects that essentially requires only two views to read.

FRONT VIEW SIDE VIEW

Figure 5.2 A drawing of an object requiring three views to interpret correctly.

drawing" has come into general use, indicating that more than one view is used to illustrate an object, but the terms are essentially synonymous. "Orthographic" comes from the Greek word for "straight writing (or drawing)." Orthographic projection shows the object as it looks from the front, right, left, top, bottom, or back, and different views are typically positioned relative to each other according to the rules of either first-angle or third-angle projection. Ortho views depict the exact shape of an object seen from one side at a time as you are looking perpendicularly to it without showing any depth.

A single view of an object is rarely adequate to show all necessary features. Figure 5.3 is an example of orthographic projection showing the six principal views used by architects and engineers in construction and industrial drawings.

Common types of orthographic drawings include plans, elevations, and sections. The most obvious attribute of orthographic drawing is its constant scale-that is, all parts of the drawing are represented without foreshortening or distortion, retaining their true size, shape, and proportion. Thus, in an orthographic drawing, a window shown to be 8 feet wide by 4 feet high will always be drawn at this size, no matter how far it is from our viewpoint (Figure 5.4).

Plans are really orthographic views of an object as seen directly from above. Floor plans are the most common form of plan; they delineate the layout of a building. A floor plan is represented by a horizontal section taken through the building or portion of a building just above the windowsill level. In addition to the arrangement of rooms and spaces, floor plans need to show the location of various architectural elements such as stairs, doors, and windows and details such as wall and partition thickness. Generally, the greater the scale of a drawing, the more detail that it is expected to contain (Figure 5.5). Thus, a drawing at a scale of 1/4" = 1'0" will typically contain more information and show more detail than a drawing at a 1/8" = 1'0" scale. Likewise, a scale of 1:2 is greater than that of 1/4 inch = 1 foot, 0 inches. Other types of plans used in building construction may include site plans, which typically show the layout of a site; foundation plans. which show the building structure; and reflected ceiling plans, which are normally used to locate light fixtures and design features.

Two important rules that must be adhered to in orthographic drawing are the placement and alignment of views, depending on the type of projection to be used. These rules are discussed below. In addition, projection lines between the views must be aligned horizontally and vertically.

Orthographic (multiview) projection is a generally accepted convention for representing three-dimensional (3D) objects using multiple dimensions (2D) of the front, top, bottom, back, and sides of the object. In practice, the minimum number of views possible is used to describe all the details of the object. Usually, a front view, top, and single side view are sufficient and are oriented on the paper according to accepted convention. Figure 5.6 represents a multiview projection for a simple house. The projection clearly shows that it is a form of parallel projection, and the view direction is orthogonal to the projection plane. Isometric projection attempts to represent 3D objects using a single view. Instead of the observer viewing the object perpendicular to it, the object is rotated both horizontally and vertically relative to the observer. There are rules and conventions to guide the creation of both types of projections. Additionally, either of them can be supplemented with various types of dimensions.

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Orthographic Multiview Drawings And Projections - Building Codes

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For many years architects and engineers have utilized a system known as orthographic projection to accurately represent three-dimensional objects graphically on paper. In recent years the term "multiview 0 Diameter Figure 5.1A An example of a simple drawing of objects that essentially requires only two views to read.

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ENGINEERING DRAWING | MULTIVIEW PROJECTION

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Pictorial drawings are not often used for construction purposes. However, on some working drawings pictorial views are used to reveal information that orthographic views alone would be incapable of showing; other situations may require a pictorial drawing essentially to supplement a major view. Pictorial projection, unlike multiview projection, is designed to allow the viewer to see all three primary dimensions of the object in the projection. Pictorial architectural drawings and renderings are very easy to understand and are therefore used extensively to depict a three-dimensional view of an object and for explaining project designs to laypersons for sales-presentation purposes. They enable an inexperienced person to interpret drawings and quickly visualize the shape of individual parts or various components in complicated mechanisms. To convey as much information as possible, the view is oriented to show the sides with the most features. In many cases, orthographic (multiview) drawings provide information in a format that makes it difficult for laypersons to visualize the total project.

Orthographic/multiview drawings are typically dimensioned and are usually drawn to a specific scale (Figure 5.23). Although pictorial drawings may be dimensioned and drawn to scale, their main purpose is to give a three-dimensional representation of the building or object. As illustrators often take artistic liberties with scale and proportion, the reader should only use pictorial drawings for general reference. And although they are not usually dimensioned and exact scaling is not required, proportions are nevertheless expected to be maintained. When pictorial drawings are dimensioned and contain other specifications that are needed to produce the part or construct the object, they are considered to be working drawings.

Whereas a multiview drawing is designed to focus on only two of the three dimensions of the object, a pictorial drawing provides an overall view. The tradeoff is that a multiview drawing generally allows a less distorted view of the features in the two dimensions displayed while lacking a holistic view of the object (thus needing multiple views to fully describe the object).

The same dimensioning rules that apply for an orthographic/multiview drawing also apply to a pictorial drawing. These include:

* Dimension and extension lines should be drawn parallel to the pictorial planes.

* When possible, dimensions are placed on visible features.

* Arrowheads lie in the same plane as extension and dimension lines.

* Notes and dimensions should be lettered parallel to the horizontal plane.

The three main types of pictorial drawings that are extensively used in architectural presentations are perspective drawings, isometric drawings, and oblique drawings.

The main difference between isometric and typical perspective drawings is that in the latter the lines recede to vanishing points. This gives the drawing a more realistic appearance but is technically inaccurate. Isometric drawings, on the other hand, show true dimensions. However, they create an optical illusion of distortion, mainly because the human eye is accustomed to seeing long object lines recede. For this reason, isometric drawings are primarily utilized for clarification of small construction details, since they depict their true size dimensions. In an oblique drawing two or more surfaces are shown at one time on one drawing. The front face of an object is drawn in the same way as the front view of an orthographic sketch.

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Pictorial Drawings - Building Codes - Northern Architecture

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Pictorial drawings are not often used for construction purposes. However, on some working drawings pictorial views are used to reveal information that orthographic views alone would be incapable of showing; other situations may require a pictorial drawing essentially to supplement a major view.

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diagram of something cut in half - Google Search

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