The Camera View Vector

What's this about?

A powerful way to think about your synthetic camera setup is in terms of the view-vector. Ideally you need to be able to position both the eye point and the focal point using model coordinates so you can accurately simulate a view in your building or environment. In addition, by understanding how the view vector of computer graphics relates to the terminology of traditional drawing, you can produce appropriate graphic output in a controlled way.

1-point vs. 2-point vs. 3-point Perspectives

When constructing a perspective by hand, there is quite a bit of procedural difference between drawing a "1-point," "2-point," or "3-point" perspective. It seems like there are different ways of drawing these three sorts of drawings, but in fact the 1-point and 2-point drawings are simply "degenerate" forms of the 3-point (generic) perspective.

You control which kind of drawing you get by controlling the location and orientation of the virtual camera relative to the geometry of the model. As shown in the illustration, if your camera is perpendicular to the main alignment of the geometry, you will get a 1-point perspective. If the view vector is parallel to the ground, but NOT perpendicular to a face, you get a 2-point perspective, and if the view vector is in a totally arbitrary orientation, as on the right, you will get a 3-point perspective.

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