Oblique projection

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 side or top.

Principles of Oblique Projection

Oblique projection is characterized by the use of parallel lines that are drawn at an angle to the projection plane. Unlike orthographic projection, where the projection lines are perpendicular to the plane, oblique projection allows for a more flexible representation of objects.

In oblique projection, the object is oriented such that one face is parallel to the projection plane, and the other faces are projected at an angle. This results in a distortion of the dimensions along the axes that are not parallel to the projection plane.

Comparison of different graphical projections

Types of Oblique Projection

There are two main types of oblique projection:

• Cavalier projection: In this type, the projection lines are drawn at a 45-degree angle to the projection plane. The scale along the receding axis is the same as that of the other axes, meaning that the dimensions are preserved.

• Cabinet projection: Here, the projection lines are also drawn at a 45-degree angle, but the scale along the receding axis is halved. This results in a more realistic representation of the object, as it reduces the distortion.

Diagram of oblique projection on the yz-plane

Applications

Oblique projection is widely used in technical drawing, engineering, and architecture. It is particularly useful for creating quick sketches and visualizations where a simple representation of the object is sufficient. The technique is also employed in video games and computer graphics to create a pseudo-3D effect.

Comparison with Other Projections

Oblique projection differs from other types of projections such as isometric projection and perspective projection. In isometric projection, the angles between the projection of the axes are equal, and the scale is uniform along all axes. Perspective projection, on the other hand, involves converging lines that mimic the way the human eye perceives depth, resulting in a more realistic image.

Various projections of a cube above a plane

Advantages and Disadvantages

The main advantage of oblique projection is its simplicity and ease of use. It allows for a straightforward representation of objects without the need for complex calculations. However, the distortion inherent in oblique projection can be a disadvantage, as it may not accurately represent the true dimensions of the object.

Related Pages

• Orthographic projection
• Isometric projection
• Perspective projection
• Technical drawing

Comparison of oblique projection from the top view

Comparison of oblique projection from the front view

Example of a piece in cavalier perspective