A parallel projection is a projection of an object in three-dimensional space onto a fixed plane referred as the projection plane or image plane, where the rays, known as lines of sight or projection lines are parallel to each other. The projection is referred to as orthographic if the rays are perpendicular to the image plane and oblique or skew if they are not.
Parallel projections are popular in technical applications, since the parallelism of an objectâ€™s lines and faces is preserved, and direct measurements can be taken from the image. Among the parallel projections, orthographic projections are the most realistic and are commonly used by engineers whereas certain types of oblique projections such as cavalier projection, military projection are very simple to implement and are used to create quick and informal pictorials of objects.
A perspective projection can be described as the projector lines (lines of sight) that converge at the center of projection, which results in many visual effects of an object. Perspective projection depends on the relative position of the eye and the viewplane. A perspective projection of an object is often considered more realistic than a parallel projection, since it nearly resembles human vision and photography.
An important property of perspective projection is that it preserves straight lines; this allows us to project only the end-points of 3D lines and then draw a 2D line between the projected endpoints.
Characteristics Of Perspective Projection
- Types of perspective projection include: one-point, two-point and three-point perspective projection.
- Perspective projection cannot give the accurate view of object
- Perspective projection represents the object in three dimensional way
- Perspective projection forms a realistic picture of object
- In perspective projection, the distance of the object from the center of projection is finite.
- Projector in perspective projection is not parallel.
- Perspective projection cannot preserve the relative proportion of an object
- The lines of perspective projection are not parallel
Characteristics Of Parallel Projection
- There are two types of parallel projection, that is, orthographic and oblique parallel projection.
- Parallel projection can give the accurate view of object.
- Parallel projection represents the object in a different way like telescope.
- Parallel projection does not form realistic view of object.
- In parallel projection, the distance of the object from the center of projection is infinite.
- Projector in parallel projection is parallel.
- Parallel projection can preserve the relative proportion of an object.
- The lines of parallel projection are parallel.
Perspective Vs. Parallel Projection In Tabular Form
BASIS OF DIFFERENCE | PERSPECTIVE PROJECTION | PARALLEL PROJECTION |
Description | A perspective projection can be described as the projector lines (lines of sight) that converge at the center of projection, which results in many visual effects of an object. | A parallel projection is a projection of an object in three-dimensional space onto a fixed plane referred as the projection plane or image plane, where the rays, known as lines of sight or projection lines are parallel to each other. |
Types | One-point perspective Projection. Two-point perspective projection. Three-point perspective projection. | Orthographic parallel projection Oblique parallel projection. |
Accurate View Of Object | Perspective projection cannot give the accurate view of object. | Parallel projection can give the accurate view of object. |
Object Representation | Perspective projection represents the object in three dimensional way. | Parallel projection represents the object in a different way like telescope. |
Realistic View of Object | Perspective projection forms a realistic picture of object. | Parallel projection does not form realistic view of object. |
Distance Of The Object From The Center Of Projection | The distance of the object from the center of projection is finite. | In parallel projection, the distance of the object from the center of projection is infinite. |
Projector | Projector in perspective projection is not parallel. | Projector in parallel projection is parallel. |
Preservation Of Relative Portion Of An Object | Perspective projection cannot preserve the relative proportion of an object. | Parallel projection can preserve the relative proportion of an object. |
Lines Of Projection | The lines of perspective projection are not parallel. | The lines of parallel projection are parallel. |