Choosing a projection - the architect's pocket reference
Projection is the way a three-dimensional object is flattened onto a two-dimensional sheet. The choice of projection determines how the drawing reads, how easily it can be measured, and how convincingly it represents the real object. The four families below cover virtually every drawing situation a designer will encounter; the rules for choosing between them have been stable for a century. For a side-by-side comparison see our iso vs axo vs perspective guide.
Isometric - equal in every direction
Isometric projects all three principal axes at 30° from horizontal, equally spaced 120° apart. Equal foreshortening on every face means a 5 mm cell on the page represents 5 mm on every face of the modelled solid. Isometric is the workhorse of mechanical and product sketching, and a long-standing favourite for furniture, joinery and architectural concept work.
Reach for it when: you need a measurable pictorial that treats every face equally - exploded assembly drawings, mechanical part studies, furniture concepts, brickwork coursing, masonry studies.
Axonometric - a category, not a single projection
Axonometric is the umbrella term for parallel pictorial projections that aren't strictly isometric. Three sub-families dominate practice:
- Dimetric (e.g. 30°/60°) - two equal axes plus a different third. Useful when one face of the object deserves emphasis.
- Trimetric (e.g. 30°/30°) - three independent foreshortening factors. The most photographically convincing of the parallel projections, at the cost of being harder to measure directly.
- Cabinet / cavalier (oblique) - frontal face stays true-shape; depth runs at 45°, normally at half scale. Unbeatable for any object whose primary face is the one the viewer should read first.
- Planometric - true plan rotated 30° or 45°, verticals erected straight up. The classic British architectural axonometric.
Reach for it when: one face deserves emphasis, when patent illustrations rule out perspective, or when video-game tile mock-ups (the classic 2:1 dimetric) demand a regular angled grid.
Browse axonometric templates →
Perspective - the eye of the beholder
Perspective replaces measurable parallel projection with vanishing points, producing the most photographically convincing pictorial of all the families. It sacrifices direct measurability for naturalness and dramatic effect. Reading list: A working illustrator's perspective bookshelf covers the canonical references.
- 1-point - single vanishing point on a centred horizon. Use it for corridors, tunnels, head-on streetscapes, atria seen down their length.
- 2-point - two vanishing points on opposite ends of the horizon, well outside the printed frame. The standard scaffold for any view that catches a building on its corner.
- 3-point - two horizon vanishing points plus a third either far above (worm's-eye view of a tower) or far below (bird's-eye view into an atrium). The most dramatic and the only honest representation of tall buildings observed from street level.
- Curvilinear / fisheye - five-point construction that bows lines outward from the centre, mimicking what a wide-angle lens or human peripheral vision actually sees.
Reach for it when: you need to communicate spatial experience rather than measured proportions - competition sketches, client presentations, urban-design vignettes, cinematic establishing shots in storyboards.
Browse perspective templates →
Cross-section (orthographic) - the measured view
Cross-section grids are the millimetre and centimetre lattices of orthographic drawing - pure plan, elevation, or section, projected at right angles to the page. The classic three-weight ruling - faint 1 mm cells, medium 5 mm subdivisions, bold 10 mm reference lines - gives the eye a measuring framework without competing with the drawing on top.
Reach for it when: the drawing must be measurable above all else - engineering details, planning-application drawings, tender drawings, lab notebook plots, hand-plotted graphs.
Browse cross-section templates →
The pocket decision tree
- Need a measurable pictorial that treats every face the same? Isometric.
- Need to emphasise one face? Cabinet (frontal view) or dimetric (any face).
- Need photographic realism in one direction? 1- or 2-point perspective.
- Need to honestly represent a tall building from street level? 3-point perspective.
- Need to measure off the page? Orthographic / cross-section.
- Need to communicate sequential experience over time? Storyboard.
The right projection is the one whose strengths line up with the question you're trying to answer. GridCraft publishes calibrated grids for every family above, so the decision becomes about communication rather than about what kind of paper happens to be in the studio drawer.