ZIMSEC O Level · Technical Graphics and Design · Form 1, Form 2, Form 3
Pictorial drawings show an object in three dimensions in a single view.
Isometric drawing
- Vertical lines stay vertical; horizontal edges are drawn at 30° to the horizontal.
- All measurements along the three axes are true lengths.
- Circles appear as ellipses: construct them using the four-centre method or plotted points.
- Start with a box (crate) enclosing the object, then cut away.
Oblique drawing
- The front face is drawn true shape and true size.
- Receding lines are drawn at 45°.
- Cavalier oblique: receding lines full length. Cabinet oblique: receding lines half length (looks more realistic).
- Place the face with circles or the most detail at the front.
Perspective (introduction)
One- and two-point perspective use vanishing points on a horizon line to show depth realistically.
Freehand sketching
Quick sketches using light construction lines help develop and communicate design ideas.
Exam tip: In oblique drawing, put curves and circles on the front face, where they keep their true shape.
Check yourself
- At what angle are horizontal edges drawn in isometric?
- What is the difference between cavalier and cabinet oblique?
- How does a circle appear in isometric?
Show answers
- 30° to the horizontal.
- Cavalier uses full-length receding lines; cabinet uses half-length receding lines.
- As an ellipse.
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