Plan oblique and Isometric Technical Drawings

So within this blog we have visited the different projection techniques we can use to represent our interiors, buildings and objects etc. We have highlighted how to draw plans, elevations and sections, and understand how important they are when bringing a design idea to paper and presenting them to a client. We have mastered 1-point perspective, 2-point perspective and 3-point perspective, increasing our ability to draw a space from a true perspective view.

This session was spent studying and delving deeper into the third pictorial system, plan oblique and isometric drawing. Plan oblique and isometric drawings are just great ways of drawing the interior from  an angle perspective, highlighting all elements including the floor plan, walls, doorways, furniture etc. lets look at the two in more detail.

Plan Oblique

(Fig 1.) A basic diagram of building plan drawn in plan oblique
(Fig.2) An interior in plan oblique

In a plan oblique drawing, the floor plan can be used as the basis for the drawing, and then each object can be elevated vertically. It is important to keep the room dimensions within the drawing, this is done by creating dimensions for each object which are a true representation of the scale and then drawing them up using a scale ruler. A plan oblique drawing rotates the floor plan 45 degrees, in some cases 30/60 degrees depending on the plan, all objects, furniture etc. will then be projected vertically to make it 3-D and oblique.

Isometric drawings

(Fig.3) A basic building interior drawn isometrically, it can be seen here how the horizontal lines in the width and depth planes are shown at 30 degrees to the horizontal. isometric drawings appear slightly more distorted but works better in most cases.
(fig.4) drawing an object isometrically.

Isometric drawings again require the floor plan to be projected vertically, this time with the ground plane axes being drawn at 30 degrees, which makes this drawing appear slightly distorted; all elements within the plan which are parallel to the ground plane will be drawn at a 30 degree angle.

Self directed

After understanding the use of plan oblique and isometric drawing and their appliance within design planning, it was then our turn to have a go at drawing up a couple of isometric and oblique drawing plans ourselves working within the following scaled dimensions:


The instructions were as follows:

  1. Draw the room plan (using the information above) in both isometric and plan oblique.
  2. Draw the remaining 2 orientations with the plan oblique technique
  3. Draw the remaining 2 orientations with the isometric technique
(Fig.6) drawing circles in isometric

Before starting on the plans, we first understood isometric and oblique drawing by practicing with drawing circles. We drew a circle to fit perfectly within a square meaning that all of the sides of the circle touched all of the sides of the square as seen on the second drawing in Fig 6. To then make this diagram oblique we rotated it 45 degrees clockwise and then project the circle vertically making the object 3-D, as seen within the bottom diagram in Fig 6.

(Fig.7) Two of the same diagrams drawn in plan oblique, we practiced rotating the diagrams twice simply to get used to different situations, and rather understanding the art of drawing in oblique. This construction formed from a flat base (floor plan) all elements were then projected vertically to make a 3D drawing.
(Fig.8) This is the same diagram as shown in (Fig.6) except drawn isometrically. The plan appears flatter than a plan oblique drawing and slightly less raised, as the ground planes are only angled at 30 degrees.

Isometric and Oblique drawings are just a very convenient way for designers to construct a quick 3D sketch for the client of what the final interior/building will look like, it gives a more true accurate vision than a floor plan as all furniture and additional objects can be seen more clearly. The main difference in the aesthetics of an isometric and oblique drawing is that an isometric drawing will put more emphasis on the edge of the interior/building, whilst an oblique drawing tends to focus more on the face or front of the interior/building.


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