Objects can project {geometric projection} onto planes. Plane figures {plane of projection} {projection plane} {image-plane} can transform to objects {image-picture} by one-to-one correspondence. Lines {projection ray} can join corresponding points from figures to images.
Projections {axonometric projection} can keep vertical lines vertical, have main horizontal axis at angle 45 or 30 degrees to verticals, and have third dimension at angle of 45 or 60 degrees to main horizontal axis.
Projections {isometric projection} can have all vertical lines stay vertical, and both other axes at angle 60 degrees to verticals.
Projections {oblique projection, object} can keep all vertical lines vertical, have main horizontal axis at right angle to right of verticals, and have third axis at angle 45 degrees to left of verticals. Oblique projection has projection rays not perpendicular to the plane.
Parallel projection {orthogonal projection, geometry} {orthographic projection, orthogonal} can have projection rays perpendicular to the plane. Orthogonal projection can be on horizontal plane {horizontal projection} {plan, projection}, vertical plane {elevation, projection}, or other planes {section, projection}. Plans {figured plan} can mark vertical distances from plane to figure.
Orthogonal projection {first angle projection} can be on bottom horizontal plane {plan projection, first angle}, back left vertical plane {front elevation, first angle}, and back right vertical plane {side elevation, first angle} {end elevation, first angle}. Front and plan are like looking into far lower corner from outside room.
Orthogonal projection {third angle projection} can be on top horizontal plane {plan projection, third angle}, front right vertical plane {front elevation, third angle}, and front left vertical plane {side elevation, third angle} {end elevation, third angle}. Front and plan projections are like looking into top front corner from outside room. This projection makes common edges closer and is usually better.
All three dimensions can be in one picture {pictorial projection}.
Pictorial projection {metric projection} can be to scale.
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Date Modified: 2022.0225