Orthographic Projections

The simplest from parallel projection is orthographic projection (is used commonly in engineering drawings). In this case we correctly represent the true size and shape of a planar face of the object. Orthographic projection is a projection on one of the coordinate planes x = 0, y = 0 or z = 0. The projection matrix onto the plane z = 0 has the form:

(2.29)

Note that in the third column (column z) all elements are zero. Consequently, the transformation coordinate z of the coordinate vector will be zero.

Similarly forming the matrices for the projection on the plane x = 0 and y = 0:

(2.30)

(2.31)

One orthographic projection does not give enough information to recreate the visual and practical form of the object. Therefore for practice it is necessary to form several orthographic projections.

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