The principal volumes of the traditional sedan can be split into separate compartments or boxes: the hood/bonnet is the first box; the passenger compartment the second, and the trunk/boot the third - i.e. it's a 'three-box' car. A three or five-door hatchback (no separate trunk compartment) is a 'two-box' car.

A 'one-box' design is achieved by pulling the base of a hatchback's A-pillars and screen forward, but unlike cab-forward designs, the driver and passenger are left where they are. The impression from within is one of spaciousness - though the space gained is largely unusable

One-box designs communicate extra size or volume: the spacious and versatile 1997 Mercedes A-Class is actually shorter than the current, cramped Mini. The main drawbacks are the shift of the A-pillars from the drivers' peripheral vision towards his direct field of vision, and solar gain from the panoramic windscreens.

Though Fiat might challenge the claim, the 1992 Renault Twingo is generally regarded as the first mass-produced one-box car. Commercial vehicles with 'forward control' seating have been one-box for years which is perhaps why Americans refer to their MPVs as 'vans'.

Although 'artistic license' with perspective, proportion (and wheel diameter) may be expected and understood in both 2-D and 3-D, the reality exists in the package drawing. Drawn over a 'tens lines' grid to a stated scale, it can be measured.

Typically, the package drawing is delivered, via the engineers, to designers as an assembled collection of largely non-negotiable 'hard points' in the form of the unclothed functional contents of a car. This will include recommended length, width and height, wheel centers, engine, drivetrain and fuel tank location, screen angle and position, maximum and minimum percentile manikin positions (with sightlines) which will also impact on the interior's design, as will inner wheelarch intrusion, etc.

In 2-D elevation, or 3-D CAD form, all this will provide the initial underlay over and around, which a designer will have to demonstrate his sketches can be persuaded to fit - without loss of 'character'.

See also package

The Approach Angle is measured by drawing a tangent from the leading edge of a front tire upwards to the lowest point on the front overhang.

The Departure Angle, by a line similarly drawn from the trailing edge of a rear tire to the lower rear overhang.

The Breakover Angle is that created by drawing tangents from the trailing edge of the front tire, and the leading edge of a rear tire to meet at the center point under the sill/rocker panel.

There is no legislation covering ramp angles, but maximizing them is functionally critical on off-road vehicles and of cosmetic interest to owners of sports cars with minimal ground clearance. 

A rendering is the definitive expression of a design idea. Although light, shade, color and reflections - all possibly computer-enhanced (typically using Photoshop) - may be expected 'ingredients' of a rendering, it has more to do with the precision, accuracy and care with which a design is described. This is quite likely to be 'sharpened' by the use of drawing aids such as ellipse guides and French curves.

Photo-realistic definition won't be required between designers well used to looking at, enjoying and 'interpreting' sketches, but is necessary to explain and sell a design idea to, for example, non-designer clients in decision-making roles (such as senior management). In some cases, common views and colors may even be stipulated to remove preference between competing renderings.

(See also concept sketch, rendering, package drawing, tape drawing, underlay)

Drawing is still regarded as the language of designers. Sketches are an important visual expression of a designer's creative thought process, but not generally the end product.

Sketches are used as an aid to evolving and visualizing an idea. Initially they will be rapid, exploratory and ‘evocative' rather than definitive - trying to catch the 'spirit' or 'mood' of the idea. The line quality, detail and form definition will become clearer as an idea is developed (hence sometimes, development sketch) until it is resolved in a rendering. A sketch is, by definition, unfinished, though most designers prefer the relaxed 'atmospheric looseness' and 'un self-consciousness' of sketches.

There is debate about whether sketching is a thinking process in itself, whether the thinking and sketching are 'simultaneous', or whether the thinking is done 'normally' and transmitted, via the hand, to paper, for appraisal by the eye.

Sketches are not generally made for other people and development sketches or 'thinking drawings', complete with center, section and perspective construction lines, may never actually be seen. In this sense, if they have no development potential, sketches can be thought of as 'disposable' rather than ‘precious'. Having said that, these are an important record of both a designer's range of ideas and the ability to develop any preferred idea.

Favorite weapons are a soft, blue Prismacolor or Derwent pencil (which easily produce expressive lines) or, for the more skilled, a Biro (which doesn't) on thin 'layout' paper. Sketching may also be done on the computer using Photoshop, but most designers find the lack of 'immediacy' inhibits the process. The expression 'napkin sketch' defines the notion of 'immediacy'.

In the creative sequence, the sketch model is used as a 'quick and dirty' (and cheap) means of translating a 2-D sketch into 3-D to make sure that the essence of the graphically successful sketch is not lost - or indeed, to confirm that the translation is actually possible. As with the sketch, the sketch model is a means to an end, not an end in itself.

For students, this will mean a small-scale - 1/10 will do it - blue Styrofoam model; for the professionals it's more likely to be a ¼ scale clay model. For both, there is the 3-D computer-modeling (usually using Alias software) alternative, the simple objective being to map-in the broad surfaces and, importantly, check the conjunctions of these surfaces. As these 3-D renderings are developed they may be checked in 'real' 3-D by milling a rough foam or small rapid-prototyped 'wax' model before committing considerable resources to milling-out a full-size model either in clay or high-density foam.