Re-visiting the post on Daniel Lebeskin's drawings reminded me that I had a draft post on technical drawing that needed adding to. I am always interested in how small differences in appearance can mean a lot when constructing a drawing and this is the same when dealing with technical drawing as it is with more expressive drawing conventions.
Most technical drawing systems were determined by draftsmen who needed to ensure their drawings could be read by the people who worked from them. Therefore one of the key issues was that measurements could be transferred accurately.
In a perspective drawing things get smaller as they recede away from the picture plane, this gives a powerful and convincing depiction of objects moving away from us, but for an engineer this is far too 'emotional' to have any direct use value. A technical drawing focuses on 'the object' of the drawing, whilst a perspective drawing is orientated towards the viewer and highlights the relativity of the viewer/object duality.
One way of thinking about the difference between the types of technical drawing systems is where the initial visual interest lies. Plans, sections and elevations (orthographic drawings) indicate two dimensional thinking, whilst axonometric drawings use the three axes of length, width and height for measurement and all measurements in these directions are made parallel to these axes. They are literally three dimensional.
A plan is also about shaping up an idea, a plan reduces three dimensional complexity and by reducing the amount of information allows you to concentrate on specific aspects of an idea of something.
The drawing above by T.N. Architecture is concerned with an idea of 'narrative cities' stories about a city's formation, function, and ideology. The city is seen from above and events are moving, lines contact one another and each line has a different character expressing a different function or idea. It is a plan, an idea of a possibility and both artists and architects understand how powerful plans are.
Bruce Nauman: Exhibition plan
The drawing above is by the artist Bruce Nauman and is a plan for an exhibition. He is thinking carefully about how to articulate the spaces and where projectors need to go. The plan view allows him to focus on the problem.
In an isometric projection the focus is on the edges of a shape, and by drawing the sides moving off at 30 degree angles, an equal emphasis on both sides of a space or object is maintained. If you look at the drawings below you can get a very clear idea of their three dimensional shape and both sides of these objects are given equal visual weight.
In the drawing below by Osbert Lancaster we have an 'almost' isometric drawing. There is a touch of perspective added by shifting the drawing slightly off the underlying parallel lines. If you look at the angle made by the back edge of the drawing it would eventually meet at a long away vanishing point the angle coming from the front edge. This compromise is fine for a cartoonist but would be of no use for an engineer. The point here being that as an artist you can merge or blend together different types of visual projection in order to achieve the type of space that works for your idea.
Isometric: Osbert Lancaster
The image above by Escher uses the spatial ambiguity of an isometric projection to allow him to develop spatial paradoxes. See more thoughts on these issues here.
Oblique: cavalier projection by Chris Ware
In the oblique projection used by Chris Ware the emphasis is placed directly on an entry into the space from the front edge of the image. As you move into the space it is cut into by slices making it harder to read what is in spaces further back in the drawing than it would be if an isometric had been used, but Ware is aware of this and his spaces are made to control and host uncomfortable psychological narratives. Oblique projections are usually drawn using either 45 or 63.5 degree angles. There are two sorts, cavalier and cabinet projections. In the drawing above we can enter the space from the front and the right hand side. In comparison the Osbert Lancaster drawing feels a little less constrained and regimented.
In a Cavalier projection the direction of projection is at 45 degrees to the horizontal and line lengths are as measured.