Types of Projections

There are several different projection methods available to computer-generated visualizations, each one with its own benefits.

Perspective Projection

The Dragon PLY model Rendered with ezViz Batch Mode (deprecated) with a Perspective Projection
The Dragon PLY model Rendered with
ezViz Batch Mode (deprecated) with a Perspective Projection

Perspective Projections are the closest to "real-life" projections. The image is rendered similar to how it would appear to the human eye, so that there is a vanishing point and objects in the distance are smaller than objects closer to the viewer. Unfortunately, parallel surfaces will bend and distort to the vanishing point. In the dragon image shown, the bounding box is a perfect rectangular object, but the top and bottom sides appear to be pointed toward each other due to warping caused by the fact that they are oriented away from the viewer.

Orthographic Projection

The Dragon PLY model Rendered with ezViz Batch Mode (deprecated)with an Orthographic Projection
The Dragon PLY model Rendered with
ezViz Batch Mode (deprecated) with an Orthographic Projection

Orthographic projections (also known as parallel projections) are popular in CAD programs. In an orthographic projection there is no vanishing point, so that surfaces and lines that are parallel in real-life remain parallel in the rendering. Also, objects do not get smaller in size as they move away from the viewer, making measurement and scaling much easier. Unfortunately, it becomes impossible to determine distance with non-overlapping geometry. (e.g., two cubes placed apart at different distances to the viewer, will both appear identical).


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