Difference Between Parallel and Perspective Projection in Computer Graphics

Parallel Vs. Perspective Projection: Know the Difference Between Parallel and Perspective Projection in Computer Graphics

Projection is the process of mapping the three-dimensional points on a plane that is two-dimensional. There are basically two major types of projections. In this article, we will discuss the difference between parallel and perspective projection in computer graphics. But let us first know a bit more about each of these individually.

What is Parallel Projection?

This type of projection is helpful for the engineers and architects who create the working drawings of any object. They require a complete representation of these objects with two or more views on different planes. That’s where parallel projection comes into play.

Parallel projection helps a person display the intended picture in its true size and shape. The created projection is known as orthographic when it is perpendicular to the available view plane. The extending parallel lines emerging from all the vertices of an object form a parallel projection by intersecting on the plane of the available screen. This point of intersection is known as the vertex.

What is Perspective Projection?

This type of projection is useful for the people who draw three-dimensional scenes, such as artists. Such people don’t require the true size and shape of an object- they only require the visual representation of that object on a three-dimensional plane.

The lines of projection from an object do not remain parallel in a perspective projection. They converge finally on a single point (also called the center of projection). We obtain the projection of an image on a screen by the intersection points of the lines converging with the screen’s plane. The image that we obtain on the screen appears as if the viewer’s eyes are present at the very center of the projected object. The lines of this projection correspond to the path traveled by the beams of light originating from the object.

Perspective foreshortening and vanishing points are the two primary characteristics of perspective. The overall length and the objects present in a 3D world appear smaller due to perspective foreshortening. The more distance we create from the center of projection- the smaller the objects will appear on the plane.

Difference Between Parallel and Perspective Projection in Computer Graphics

Here is a list of the differences between Parallel and Perspective Projection in Computer Graphics.

Parameters

Parallel Projection

Perspective Projection

Representation of Objects

It represents any given object in a different way- as we view it on a telescope.

It represents any given object in a three-dimensional manner.

Shape and Size of Objects

It does not alter the shape or the size of the given object on a plane.

In this perspective, the objects that stay far away appear to be smaller in size, while the ones near to the viewer’s eyes appear bigger in size.

Distance from Center of Projection

The distance of the given object is infinite from the center of the projection.

The distance of the given object is finite from the center of the projection.

Accuracy of View

It can provide a user with an accurate view of the given object.

It cannot provide a user with an accurate view of the given object. The shapes and sizes of the projection tend to differ from its origination.

Lines of Projection

The parallel projection lines are parallel to each other.

The perspective projection lines are not parallel to each other.

Projector

The projector is also parallel.

The projector is not at all parallel.

Types of Projection

There are basically two types of parallel projections:

  • Oblique
  • Orthographic

There are basically three types of perspective projections:

  • One Point
  • Two Point
  • Three Point

Realistic View

Parallel Projection does not form a realistic view of the world and its objects.

Perspective Projection generates a very realistic view of the world and the objects present in it.

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