Pictorial drawing techniques: HSC Industrial Technology Graphics Technologies

What this dot point is asking

Where orthogonal drawings describe an object precisely in separate flat views, pictorial drawings show it in a single three-dimensional view that is easy to understand at a glance. NESA expects you to produce isometric, oblique and perspective drawings and to explain how each represents three dimensions and where each is best used. Pictorial drawing communicates ideas quickly, so it appears throughout your design folio and is tested in the written paper.

What pictorial drawing is

A pictorial drawing shows three principal faces of an object in a single view, so the shape is understood immediately without assembling separate views in the mind. Pictorials are not usually used for full dimensioned manufacture; instead they communicate the idea, the form and the appearance, which is why they are central to design presentation and the early stages of a project.

Isometric drawing

In isometric drawing the three axes are drawn at equal angles, the vertical staying upright and the two horizontal axes going back at thirty degrees to the horizontal. Measurements along all three axes are drawn to true scale, so an isometric drawing keeps proportions accurate and can be measured along the axes. It gives an undistorted, even-looking view and is the most common technical pictorial. Its limitation is that circles become ellipses, which take more care to draw, and it looks slightly unnatural because it has no perspective.

Oblique drawing

In oblique drawing one face is drawn flat-on, in true shape and size as if you were looking straight at it, and the depth lines run back from it at an angle, often forty-five degrees. Because the front face is undistorted, oblique is quick to draw and ideal for objects with circular features on the front, since those circles stay true circles. To stop the object looking too deep, the depth is often drawn at half scale (cabinet oblique). Its weakness is that it looks distorted from some angles and is less realistic than perspective.

Perspective drawing

Perspective drawing reproduces how the eye actually sees, with parallel lines appearing to converge on vanishing points on the horizon, so distant parts look smaller:

• One-point perspective uses a single vanishing point, with the front face flat-on, suiting interiors and head-on views.
• Two-point perspective uses two vanishing points, giving a realistic corner-on view of an object or building.

Perspective is the most lifelike method and is used for presentation and architectural visuals, but measurements cannot be taken directly from it because everything is foreshortened.

Choosing a pictorial method

Select by what you need from the drawing:

• Isometric: when you want a clear, measurable technical view with even proportions.
• Oblique: when speed matters and the object has important circular features on one face.
• Perspective: when realistic appearance matters more than measurement, as in presentation and architectural work.

When you justify a pictorial choice in your folio, name the method and explain why its balance of speed, measurability and realism suits the purpose of that drawing.