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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