Oblique projection

Type of graphical projection used for technical drawings

Oblique projection is a simple type of graphical projection used for producing two-dimensional images of three-dimensional objects. It is a form of parallel projection where the projection lines are not perpendicular to the projection plane. This technique is often used in technical and engineering drawings to represent objects in a way that combines a view of the front with a view of the sides.

Principles of Oblique Projection

Oblique projection is characterized by the fact that the projection lines are drawn at an angle to the plane of projection. This angle is typically 45 degrees, but other angles can be used depending on the desired effect. The key feature of oblique projection is that one face of the object is shown in true scale, while the other faces are distorted.

Comparison of different graphical projections

In oblique projection, the object is oriented such that one face is parallel to the projection plane. This face is drawn in its true shape and size, while the other faces are projected at an angle, typically resulting in a foreshortened view.

Types of Oblique Projection

There are several types of oblique projection, each with its own characteristics:

Cavalier Projection

In cavalier projection, the projection lines are drawn at a 45-degree angle to the plane of projection. The scale along the receding axis is the same as the scale along the axes parallel to the plane of projection. This means that the dimensions along the receding axis are not foreshortened.

Example of cavalier projection

Cabinet Projection

Cabinet projection is similar to cavalier projection, but the scale along the receding axis is halved. This results in a more realistic appearance, as the foreshortening reduces the distortion of the object.

Cabinet view of a potting bench

Military Projection

Military projection, also known as military perspective, is a form of oblique projection where the projection lines are drawn at an angle that is not 45 degrees. This type of projection is often used in military applications to represent terrain and fortifications.

Military perspective example

Applications of Oblique Projection

Oblique projection is widely used in technical drawing and engineering because it allows for a clear representation of the front and sides of an object. It is particularly useful for illustrating complex objects where the internal structure needs to be shown clearly.

Cavalier perspective of a fortification

Advantages and Disadvantages

The main advantage of oblique projection is its simplicity. It is easy to construct and understand, making it ideal for quick sketches and technical illustrations. However, the distortion of the object can be a disadvantage, as it may not accurately represent the true proportions of the object.

Related Pages

• Orthographic projection
• Isometric projection
• Perspective projection