PROJECTION DRAWING
A three major drawing systems result from the way
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a three-dimensional subject is projected onto a twodimensional plane of projection, or more simply, onto
the picture plane.
• Projectors transfer points on t he subject to the
picture plane. These projectors are also called
sightlines in perspective projection.
• The drawing surface or sheet of paper is the virtual
equiv
alent of the picture plane.
Three distinct projection systems result from the
relationship of the projectors to each other as well
as to the picture plane.
Orthographic Projection
• Projectors are parallel to each other and
perpendicular to the picture plane.
• Axonometric projection is a special case of
orthographic projection.
Oblique Projection
• Projectors are para llel to each other and oblique to
the picture plane.
Perspective Projection
• Projectors or sightlines radiate from a central
point that represents a single eye of the observer.
Once the information for a three-dimensional
construction or environment has been entered into
a computer, 3D CAD and modeling software can
theoretically present the information in any of these
projection systems.
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I ARCHITECTURAL GRAPHICS