Isometric Projection |Difference Between an Orthographic and Isometric Projection

Isometric Projection

An isometric projection is the perspective representation of an object placed so that the three significant edges (which correspond to the three dimensions of the object) form equal angles of 120.

Unlike multi-view projection, isometric projection allows you to represent all three dimensions of an object. It, therefore, involves the use of perspective.

One does not find any horizontal edge in this type of projection. Consequently, no face of the object is parallel to the sheet. Instead, the object has one or more edges in the foreground. In this type of projection, the visual rays are perpendicular to the drawing sheet while the object is tilted relative to the latter.

Advantages of Isometric Projection

The advantage of this type of projection is that all measurements of edges parallel to isometric axes (the axes corresponding to the three dimensions of an object) correspond to the scale at the actual lengths. Therefore, we can rely on the dimensions of an isometric projection to know the real dimensions of an object.

However, the measurement of the object’s angles is not respected, and it happens, in some instances, those specific shapes are distorted (for example, the circles become oval).

Difference between an orthographic and isometric projection

The difference between these types of views lies in the fact that, in the Isometric Projection, the objects have different sizes depending on the distances they are from one another. In other words, in the Orthogonal or Orthographic view, we cannot notice the difference in size regardless of the objects’ distance.

Applications of Isometric Projection

The figures on the left are the views in a dihedral system, while on the right, an isometric projection with a partial section is seen.

In design and technical drawing in industrial design, a piece is represented from different points of view, perpendicular to the natural coordinate axes. Apart mechanical movement generally has shaped with axes of symmetry or flat faces. Such axes, or the edges of the faces, allow defining an orthogonal projection.

An isometric perspective of the part can easily be drawn from such views, allowing for a better understanding of the object’s shape.

  Isometric Projection in Architecture

The Louvre’s castle, isometric drawing by Violle, used this system in many drawings of his buildings, avoiding accentuating the importance of some volumes over others and making it independent from the observer’s point of view.

The perspective of this drawing of the castle is not isometric; if it were, the castle towers would be drawn with the same height and diameter. Besides, the roofs’ ridgelines would be parallel to each other, forming a rhombus or rhomboid depending on the castle floor.

In videogames, several videogames put their characters into action using an isometric point of view, or rather, in the usual jargon, in “3/4 perspective”. From a practical angle, this allows you to move the graphic elements without changing the size, an inevitable limitation for computers with low graphic capacity.

To avoid pixilation, in some cases, the projection was taken to a 2: 1 system, that is to say, at a 26.6º inclination (arctan 0.5) instead of 30º, which does not correspond to an isometric projection itself, but “diametric.”

The progressive increase in computers’ graphic capabilities has made possible the increasingly widespread use of more realistic projection systems, based on the perspective naturally perceived by the human eye: the conical perspective.

Common Use of Isometric Projection

Because isometric projection keeps the relative proportions of an object the same on all three axes, it is commonly used in architectural and technical drawings to allow in-plane measurements to reflect the real object or building measurements accurately. The aerial isometric perspective is also used in many computer games.

No more than four sprites are required to represent any game object, and it allows game characters to travel any distance without needing to change perspective.


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