How do isometric, planometric and oblique drawings show a product in three dimensions, and when is each used?
Pictorial drawing methods: isometric (30 degree axes), planometric (true plan rotated) and oblique (cavalier and cabinet) drawing, the axis angles and scaling of each, and choosing the right method for the object and purpose.
An SQA Higher Graphic Communication answer on pictorial drawing methods, covering isometric, planometric and oblique (cavalier and cabinet) drawing, their axis angles and scaling, and how to choose the right method for an object and purpose.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this key area is asking
The SQA wants you to draw a product pictorially (in three dimensions) by the standard methods: isometric, planometric and oblique (cavalier and cabinet), knowing each method's axis angles and scaling, and choosing the right one for the object and purpose. A pictorial shows the whole product in one view, which orthographic cannot.
Isometric drawing
Circles on an isometric face become isometric ellipses, drawn with the four-centre method or a CAD ellipse tool aligned to the relevant axes. Isometric is the default measurable pictorial: good for showing a component clearly while still letting sizes be taken along the axes.
Planometric drawing
The strength of planometric is that the top view stays true, so it shows layout (the arrangement of rooms or furniture) accurately while still giving a 3D impression.
Oblique drawing
Choosing a method
The choice depends on the object and the message:
- Isometric for a general, measurable 3D view of most components.
- Planometric for interiors and layouts, because the plan is true.
- Oblique for objects whose front face carries circles or detail, drawn true (cabinet for realism, cavalier for full depth).
Worked example
Examples in context
Furniture catalogues and assembly leaflets lean on oblique and isometric because they read instantly without specialist training. Architects use planometric to present a room layout in 3D while keeping the plan true. CAD packages can output any of these pictorials from a single 3D model, so the skill is choosing the right one for the audience, not just constructing it.
Try this
Q1. State the angle of the two horizontal axes in isometric drawing. [1 mark]
- Cue. 30 degrees above the horizontal.
Q2. State the depth scale used in cabinet oblique drawing. [1 mark]
- Cue. Half size (the depth is reduced to look realistic).
Q3. State which pictorial method keeps the plan true and is good for interiors. [1 mark]
- Cue. Planometric (axonometric).
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher (style)4 marksDescribe the axis angles and scaling used in isometric drawing and in planometric drawing.Show worked answer →
In isometric drawing the two horizontal axes are drawn at 30 degrees above the horizontal, and the vertical axis stays vertical. All three axes are drawn to the same scale (true lengths along each axis), so it is easy to take sizes from a measured drawing. No face is shown at its true shape, because every face is inclined.
In planometric drawing the plan is drawn true (its true shape, often rotated, commonly 45/45 or 30/60), so the top of the object is undistorted, and verticals are then drawn straight up from the plan. Verticals are often drawn full size, though they may be reduced (to about two thirds) to look more natural.
Markers reward: isometric = two axes at 30 degrees with equal scaling on all three axes; planometric = a true (rotated) plan with verticals projected up (often full size, sometimes reduced).
SQA Higher (style)3 marksExplain the difference between cavalier and cabinet oblique drawing, and state when oblique is a good choice.Show worked answer →
In oblique drawing one face is drawn true (full front face), and the depth is projected back at an angle, usually 45 degrees. The difference between the two types is the depth scale: in cavalier oblique the depth is drawn full size (true depth), while in cabinet oblique the depth is reduced, usually to half size, to look more realistic because full-depth oblique looks too deep.
Oblique is a good choice when an object has a complex or circular front face, because that face is drawn true (so circles stay as circles and detail is easy to draw and read) while the depth is simply projected back.
Markers reward: cavalier = full-size depth, cabinet = half-size depth, and that oblique suits objects with detail or circles on the front face, which is drawn true.
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