Topic 6 of 7 · Form 5
Pictorial projection and perspective
Isometric drawing uses true lengths on all three axes; isometric projection uses the isometric scale (lengths reduced to about 0.816 of true length), which is the true projected size.
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Isometric projection versus isometric drawing
Isometric drawing uses true lengths on all three axes; isometric projection uses the isometric scale (lengths reduced to about 0.816 of true length), which is the true projected size.
Worked example: An edge is 100 mm long. How long is it drawn in isometric projection?
100 × 0.816 = 81.6 mm
Curves in isometric
Plot circles and irregular curves using ordinates or the four-centre approximation.
Planometric and oblique projection
Planometric (plan true shape, rotated 45° or 30°/60°) for interiors; oblique (cavalier and cabinet) for objects with circular front faces.
Perspective
- One-point (parallel) perspective: one vanishing point – interiors and corridors.
- Two-point (angular) perspective: two vanishing points on the horizon line – buildings and products.
- The picture plane, station point, horizon line, ground line and measuring lines.
Rendering
Shading to show form and material; shadows; colour and texture; highlights.
Check yourself
- What is the isometric scale factor?
- Which type of perspective is best for drawing an interior view of a room?
- Where are vanishing points located?
Show answers
- About 0.816.
- One-point (parallel) perspective.
- On the horizon line (eye level).
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