A Pupil's Reference Guide To Using Graphics and

Presenting Projects in the School Curriculum

Isometric Circle Construction

To draw an Isometric circle

There are other methods that are available but the reason for starting with this method gives

the greatest long term benefit for a pupil wishing to develop their visualisation skills.

These are the drawing skills that are used when constructing and developing ideas. Unique in

the sense that the drawing outcome is not from the direct observation of objects that already exist.

The use of Drawing instruments or templates rather than just pencil and paper will inhibit the flow

of communicating ideas visually.

As pupils practice the processes shown below and as confidence grows with regard to the bounded,

ellipse position, radius of curves and tangent points where the curve changes, they can gradually

dispense with much of the visual stages of construction.

The early use of boxes surrounding the shape helps to develop the "crating" process and three-dimensional

thinking.

Fig. 1.

Shows the circle with its centre and tangent points. It is a true circle, because angles and sizes are precisely

as they are drawn.

Fig. 2

Still in a true view, the vertical and horizontal lines that bisect the square, prove the position where the inscribed circle touches the square. These are the tangent points.

The green construction lines are lines that will need to be added to an isometric version of the square. They cross the diagonal construction lines and provide the compass centre points for two of the four curves that will make up the isometric circle. ( The circle will distort from a true circle to an elliptical circle).

Fig. 3

Just drawing the isometric "Square" is a stumbling block to pupils in the early development of three-dimensional conceptualisation. Often because it is an early step used to draw representations of solid objects. Yet to the learner it is a "diamond shape". Why has it become narrower? Why can I not use the centre of the circle that was used in Fig. 1? The use of photographs with isometric crating overlaid on the image can illustrate the presence of the bare graphical shape with the benefit of the illusory presence of colour, tone, texture, shadow and reflection qualities. Thus giving the purpose for the basic isolated techniques being shown. There is no escaping the truth that it is not three-dimensional but part of the methods used to represent it.

Using the principles of angles and line length will help to create the Diamond shape. The corner to corner lines and the other lines by reference to measurement and relative position.

The green circles indicate the point position of the compass in order to draw the curves of the ellipse.

Fig. 4

Each curve is confined to the quartered part of the square. It is helpful to recognise that an ellipse differs from a true circle because its radius is not the same throughout. The diagonal lines shown on Fig 1 are equal in length, whereas on Fig 3, 4, 5, and 6 one is shorter than the other. The smaller radius of the ellipse is drawn by placing the compass point on the longer "diagonal".

Fig. 5

Shows the compass position for drawing the other quarter curve. The grey shading indicates the quarter of the ellipses drawn using the smaller curve.

Fig 6

The blue area shows the quarter of the ellipse drawn with the larger compass curve.

The lines apart from the ellipse are construction lines, so draw them thin and light.

As pupils become more proficient, judging the tightness and position of the curves will reduce the need for so much drawing construction work.

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