Orthographic projection – from a 3D object to three views
Design & TechnologyEngineering Drawing & DesignAges 13–14
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Engineering Drawing & Design
An object (a box, a wedge, an L-shaped block, a cylinder, or a hexagonal prism) rotates by mouse or touch; three orthographic views are drawn automatically and placed using first-angle projection convention: the front view on top, the top view below the front view, and the side view to the right of the front view; hidden edges are drawn as dashed lines. Change the length, width and height and watch all three views update accordingly. The 2D | 3D switch shows the actual object in the corner formed by the three projection planes (frontal plane behind, horizontal plane below, profile plane on the right), with projection rays and each view printed on its plane; the scene can be rotated.
Lesson: Orthographic projection of an object; projections of polyhedra and solids of revolution
What it shows
Orthographic projection describes a 3D object with several 2D views, each formed by parallel projection rays perpendicular to a projection plane. In first-angle projection the object sits between the viewer and each plane, so the top view is drawn below the front view and the left view to the right of it. Each view shows only two of the three dimensions: the front view shows length and height, the top view length and width, and the side view width and height. Edges hidden behind material appear as dashed lines, and a cylinder gives rectangles in two views and a circle in the third.
How to use
Choose an Object and drag the 3D view to rotate it, or press Auto-rotate, while the three views update beside it. Change Length, Width and Height one at a time and ask students which views change size. Switch Draw hidden edges (dashed lines) on and off with the L-shaped block or the hexagonal prism to see where dashed lines appear. Finally switch to 3D to show the object inside the three projection planes with its projection rays.
Parameters you can change
- Object Rectangular box, Triangular prism (roof shape), L-shaped block (step), Cylinder, Regular hexagonal prism
- Length 20–100 mm
- Width 20–100 mm
- Height 20–100 mm
- Draw hidden edges (dashed lines)
Questions to explore
- Which dimension never appears in the top view, and in which two views can you read the height?
- Why does the side view of the L-shaped block contain a dashed line while its front view does not?
- What shapes are the front, top and side views of a cylinder?
Common questions
What is the difference between first-angle and third-angle projection?
First-angle and third-angle projection differ in where the object sits relative to the projection plane, which changes where the views are placed. In first-angle projection the object lies between viewer and plane, so the top view goes below the front view and the left view to its right; in third-angle the plane lies between them, so the top view goes above and the left view to the left.
What do the line types mean in an orthographic drawing?
Thick solid lines show visible edges, thin dashed lines show hidden edges and thin chain lines of long and short dashes mark the centre lines of holes and cylinders. When a visible edge and a hidden edge fall in the same place only the visible one is drawn, because solid lines take priority over dashed ones.
How many views do you need to describe an object?
Three views are enough for most simple objects, because each view shows only two of the three dimensions and together they show all three. A shape turned around one axis may need only two views while a complex part may need extra views or a section, so drawings use the fewest views that show every feature clearly.
