Difference Between Orthographic and Isometric Projection

Pre-requisites: Projections in Computer Graphics

Representing an n-dimensional object into an n-1 dimension is known as projection. It is the process of converting a 3D object into a 2D object, we represent a 3D object on a 2D plane {(x,y,z)->(x,y)}. 

Orthographic Projection 

When the direction of the projection is normal (perpendicular) to the view plane, we have an orthographic projection. In another word, Orthographic projection means a method of representing the exact shape of a 3 Dimensional object on a 2 Dimensional sheet in two or more views.

It is also simpler than the two parallel projections. In orthographic projections, the direction of the projection is perpendicular to the projection plane. In that projection, Projectors are parallel to each other and also perpendicular to each other. It is also called a Multi-view Projection.

Advantages

• One of the advantages of this projection is it can preserve both distances and angles. 

Disadvantages

• There are so many hidden surfaces that in the real images can not clearly visible.  

Isometric Projection

In Isometric Projection, all three dimensions of an object is shown in one view. All sizes of an object can be measured directly. The issue is that an isometric projection enables the measurement of two of the three altered principal axes using the same scale factor. Measurements along the third transformed primary axis need the use of a different scale factor.

If exact scaling of the projected object’s dimensions is required, it leads to a mistake. The aforementioned problem is handled in isometric projection by keeping the three reducing components equally.

Advantages

• An isometric projection does not need multiple views. 
• The measurements can be made to scale along principal axes.

Disadvantages

• This projection is only useful for rectangular shapes.   
• This projection distorts shape and depth.

Difference Between Orthographic Projection And Isometric Projection 

Orthographic Projection	Isometric Projection
Provides a 2D view of the object.	Provides a 3D view of the object.
Each view of orthographic projection shows only one side of the object.	Isometric projection displays at least three sides of the object.
In orthographic projection, the projection plane is parallel to one of the principal planes.	In isometric projection, the projection plane is not parallel to any of the principal planes.
It does not preserve depth.	It does include depth.
The true shape and size of an object are preserved.	The projected object is foreshortened equally in all three directions.