Oct 2, 2015

AutoCAD - Prospective views

Prospective view
      Prospective view drawing is an approximate representation or image as it is perceived by the eye on a flat surface like paper.
Characteristics of prospective view
  • Smaller as their distance from the observer increases
  • Foreshortened: the size of an objects dimensions along the line of sight are relatively shorter than dimensions across the line of sight.


All prospective drawings assume a viewer is a certain distance away from the drawing. Objects are scaled relative to that viewer.
An object is even not scaled properly, a circle often appears to be ellipse and a square can appear as a trapezoid. This distortion is referred to as foreshortening.
A prospective representation of a scene that includes parallel lines has one or more vanishing points in a prospective drawing. Any number of vanishing points are possible in a drawing, one for each set of parallel lines that are angled relative to the plane of drawing.

Types of prospective:

One point prospective view
            One vanishing point is typically used for roads, railroad tracks or buildings viewed so that the front is direct facing the viewer. Any objects that are made up of lines either directly parallel with the viewer’s line of sight or directly perpendicular can be represented with one point prospective view.




Two point prospective view
            Two point prospective can be used to draw the same objects as one point prospective, rotated: looking at the corner of a house, or looking at two forked roads shrink into the distance.


Three point prospective view
            Three point prospective is usually used for buildings seen from above (or below). In addition to two vanishing points from before, one for each wall, there is now one for how those walls recede onto the ground. This third vanishing point will be below ground. Looking uo at a tall building is other common example.



            

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