Linear perspective drawing is the art of depicting a three-dimensional (3D) image onto a two-dimensional (2D) flat surface. In simpler terms, it means, creating the illusion of depth on a flat 2D sketch. In perspective, all the contents in the sketch seem to gradually decrease in size as they recede, and all the parallel lines coming out from the objects in the sketch appear to meet at one particular point.
Linear Perspective Drawing Attributes
A thin line where the Earth and the sky appear to meet each other is the horizon line, and it is always at the eye level. For example, if you are standing along the coast and looking at the ocean, you will notice that the water meets the sky at your eye level. Similarly, even when you are traveling at a height of 1,200 feet above sea level in an airplane, the line where the ocean meets the sky is still at your eye level. Hence, irrespective of where you are looking from, the horizon line always appears to be at your eye level. In terms of perspective drawing, this is the key element when portraying space in a particular sketch.
Vanishing Point (VP)
From an observer's point of view, a VP is a point where all the parallel lines seem to meet and gradually disappear. For example, parallel lines of a railway track seem to meet at a distant point.
When two or more diagonal lines are drawn on existent receding parallel lines, and when these lines meet at the vanishing point, they are known as orthogonals or convergence lines.
Types of Linear Perspective Drawings
As the name suggests, a one-point perspective drawing has one vanishing point at the horizon line. Therefore, all the receding lines coming from the object or any sketch seem to meet and vanish at the VP. Single-point perspective adds more depth to the image, and gives it an illusionary effect. One-point is usually used to illustrate railway tracks, hallways, highways, roads, corridors, and the like.
A two-point perspective is one of the most widely-used perspective drawings, as it gives a very realistic feel to the sketch. This particular perspective consists of two vanishing points on the horizon line, and this angle is generally termed as a ¾ perspective or an angular perspective. When an observer is viewing a building from its corner, all the parallel lines on the right side of the building meet at the right vanishing point, and the parallel lines on the left side of the building meet at the left vanishing point. This perspective works well in sketches that have various objects with vertical straight lines, like a group of buildings.
A three-point perspective drawing is usually an exaggerated form of illustration, and is usually drawn with the spectator either below the horizon (ant's-eye view) or above the horizon (bird's-eye view). This perspective drawing has three vanishing points, two on the horizon line and one either above or below the horizon. In the above example, we see that the right and left parallel lines of the buildings are extended and projected to the right, and the left vanishing points on the horizon line and the vertical parallel lines are projected to the third VP in the sky or the ground.
If you are looking at the building from an ant's-eye view, the topmost point is known as the Zenith (highest point), and when you look at the building from a bird's-eye view, the lowermost point, is known as the Nadir (lowest point). A 3-point perspective is used mainly for skyscrapers, and it is slightly difficult to understand as compared to the previous two types of perspectives. This is because of the third VP that is added here, and it rules out all the parallel lines.
This is a curvilinear version of a two-point perspective, and can give a panoramic or a 360° view, as the number of vanishing points surpass the least needed amount. In simpler terms, the vertical lines emerging from a two-point perspective sketch which meet at the vanishing points would now get curved at the VPs. This type of projection can be viewed both vertically as well as horizontally, and when viewed vertically, it describes a bird's-eye view, and at the same time an ant's eye-view too. In this projection, four vanishing points are equally spaced, two on the horizon line, and one above and below, to define four vertically-drawn lines in a 90° angle related to the horizon line.
An easy way to define a five-point perspective drawing would be that, it is a collection of 5 one-point perspective drawings, the difference being, it has curved lines instead of horizontal or vertical ones. The entire visual field is put together into the shape of a circle, and the lines are distorted, giving a wide-angled or a fish-eye lens effect to the image. For example, imagine yourself at the center of a globe, a five-point view allows you to see the entire half of the globe that is in front of you.
The two differences between a 5- and 4-point perspective drawing are, a five-point drawing has curved, vertical and horizontal lines, and it has a fifth point at the center (central vanishing point), both of which are not depicted in a four-point sketch.
Lesser-used Perspective Drawings
Although not heard of much, this kind of perspective is actually more common than the previous ones. It does not have any parallel lines fading at the vanishing points, hence, the name zero-point perspective. This type of perspective is used in a nonlinear scene, where there are no parallel lines meeting at a distant point; for example, in landscape drawings like valleys, mountain ranges, etc. However, a perspective projection without any vanishing points would still be able to produce an illusion of depth. For instance, when you look at a drawing or a picture of a mountain range, the mountains which are at a distance will appear smaller than the ones that are actually closer to you.
We already know that a 5-point drawing lets us view everything in front, in a 180° perspective. But the one thing that is missing here is the view that is exactly behind us. This is the sixth vanishing point, which is located exactly opposite the fifth vanishing point (behind the viewer), and it gives a 360° view, but a six-point perspective requires two separate illustrations. It is not as difficult as it might sound, as this kind of perspective is actually 2 five-point perspective drawings put together. One sphere covers what is in front and the other covers what is at the back of the viewer.
These were the different types of perspective drawings and the various purposes that they serve.