Perspective (from Latin perspicere, to see through) is an approximate representation, on a flat surface (such as paper, or the a co,puter image), of an image as it is perceived by the eye. The two most characteristic features of perspective are that objects are drawn:

  • Smaller as their distance from the observer increases
  • Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight


Types of perspective

Of the many types of perspective drawings, the most common categorizations of artificial perspective are one-, two- and three-point. The names of these categories refer to the number of vanishing points in the perspective drawing.

One-point perspective

Railroad tracks with single vanishing point above the top of the image.
Model by "EFB" from 3D Warehouse.
Rendered using IRender nXt.

One vanishing point is typically used for roads, railroad tracks, or buildings viewed so that the front is directly facing the viewer. Any objects that are made up of lines either directly parallel with the viewer's line of sight or directly perpendicular (the railroad slats) can be represented with one-point perspective.
(Model by EFB on 3D Warehouse)

Two-point perspective

Walls in 2-pt perspective.
Walls converge towards 2 vanishing points.
All verical beams are parallel.
Model by "The Great One" from 3D Warehouse.
Rendered in SketchUp.

Two-point perspective can be used to draw the same objects as one-point perspective, rotated: looking at the corner of a house, or looking at two forked roads shrink into the distance, for example. One point represents one set of parallel lines, the other point represents the other. Looking at a house from the corner, one wall would recede towards one vanishing point, the other wall would recede towards the opposite vanishing point.

SketchUp two-point perspective

SketchUp provides a special mode for two-point perspective. When this is selected, the view is changed so that vertical lines remain vertical (no vanishing point), and when panning or zooming the view, the target is moved as required so that the perspective of the image does not change. (Normally when you pan an image, the camera target is moved to the new center of the image, which causes the perspective to change.)

Three-point perspective

Three-point perspective rendered from computer model.
Model by "Noel" from Google 3D Warehouse.
Rendered using IRender nXt.

Three-point perspective is usually used for buildings seen from above (or below). In addition to the two vanishing points from before, one for each wall, there is now one for how those walls recede into the ground.

See also