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Learning perspective - Page 4 of 4 - Draw Like A Pro


Learning perspective

How to give an impression of depth

Several “tricks of the trade” work very well in drawing. You have already observed some of them such as the superimposing of two drawings, the use of shadow, relief and of course perspective. It is also possible to combine several methods. The two most often chosen by artists are relief and perspective. When used together they can lend an astonishing impression of realism to a drawing. See if you can find the different means used in these vignettes.

Visual ray and principal point Wherever you look, you “cast” a visual ray in a direction. The ray travels in a straight line from your eye to the centre of the image it perceives and moves with your eyes. Take aim with an imaginary rifle on a target. The visual ray corresponds to the trajectory of the bullet. The point where the bullet reaches the target is called the principal point.

Your vision is more or less conical. That is to say, when you look in a particular direction, the width of your vision is no more than 20 centimetres or so in the foreground , and a few hundred metres in the distance. The further you look, the wider the field around the principal point. Depending on the orientation of our visual ray, objects appear distorted to our eyes, obeying the laws of optics and perspective.

This sketch, which is deliberately short on detail, shows that the same distortion of perspective is perceived when looking at a railway track or ladder as it appears to us when stood upright against a wall, aiming towards the highest rung. The ladder is vertical, the railway line horizontal but their transposition in perspective is exactly the same. Here is the essential point to grasp: an object is distorted not according to it its position in space but according to the angle by which the visual ray reaches it.

So when you begin a drawing it is important to work out the height and orientation of your visual ray and to keep to it. This means choosing a single point of view. If you overlook this point and combine several points of view, your objects and figures will appear very awkward.

Imagine a horizontal disc centred around your head at eye level and stretching into infinity. This disc gives expression to a major element of perspective: the horizon plane.

The horizon plane is an imaginary line situated at eye level and stretching into infinity. It is marked in red in these three illustrations.

You would of course only see a section of it – a horizontal line spread over 360°.

This line is called the horizon line. Now suppose you transport yourself – along with your imaginary disc – to a coastline. This is what you would see. You would notice that the line exactly divides the landscape between the sky and the water, merging with what we usually call the horizon. While we’re at it, let’s continue to use our imagination a little.

Climb up the tallest coconut palm on the island and see if the natural horizon has now passed below the disc which you have kept at eye level. You will notice that this is not the case. The horizon, the horizontal plane, the horizon line and your eye rise and fall together. The thing to remember is that the horizon line is always situated at eye level.

It is the same with a photograph. The horizon rises with the camera.

Here are two images of the same scene. The first picture is seen by a spectator (you) whose eyes are at the same level as the figure on the right. So the two horizon planes are merged.

The second image places the observer higher up than the first one. This time, your eyes are at the level of the higher figure. The horizon plane is still merged with the natural horizon which seems to have risen at the same time as you – but be careful!

The draughtsman’s horizon plane, linked to his viewpoint, determines the height of the natural horizon. If other figures are placed below or above, they see the horizon higher up or lower down.

When you choose the height of the horizon in a drawing, you impose a point of view on anyone looking at the picture. Your choice will determine whether the spectator is in a dominant situation in relation to the subject. Look at these pictures. Try to feel the secondary effects due to the choice of viewpoint. Sharpen your artistic sensibility by trying to analyse what has an impact on you. Feel how the choice of viewpoint leaves an impression. In other words, think about the relation established between the subject (the actor) and you (the spectator). Don’t worry if it is not immediately clear to you. Your perception will gradually gain strength as you exercise it.

Here, you dominate the figure represented but in a somewhat benign way since you are looking down on him. However, his position at the centre of the picture gives him a certain importance.

This viewpoint creates an impression of confrontation between the figure and yourself. The centred composition, the horizon line placed at mid-height gives the picture a symmetry which removes the human aspect apparent in the preceding image.

This time, with the viewpoint below, the figure dominates you. He has gained a certain ascendancy over you and you seem to be in his power.

The same situation, but this time with an off-centre and very low-angle view, leaves a different impression. The figure still dominates but you yourself are not under his domination, or at least not as much as in the preceding image.

So you see, perspective is not just a tool for representing something accurately, it is also a means for enlarging your artistic vocabulary. Le cadrage Don’t confuse viewpoint with composition. The same scene, viewed from the same place, can be centred differently as a matter of aesthetic choice. The viewpoint determines perspective distortion whereas the composition selects the surface exposed to the eye.

Here are three different compositions or frames of the same picture. The result makes us feel that we are looking at three different images.

And yet the viewpoint is exactly the same.

The red line represents the horizon plane of both the figure and the spectator. The horizon plane is at the same level in all three pictures.

The framing is no more than a purely aesthetic choice of presentation or composition. Take a look at this picture. There’s something special about the perspective.

The vertical lines formed by the edge of the wall hanging, the side of the dresser and the axis of the clock remain vertical in perspective. So far so good.

The lines which are horizontal in reality, the two unoccupied sides of the table, are still horizontal when put in perspective. Is this a coincidence? What do you think?

All the other lines which are horizontal in reality, such as the shelves of the dresser and the left and right side of the table, are at an angle in the painting. What’s more, they all converge on a single point. They seem to be receding towards a precise point of the horizon. That’s why this point is known as the receding or vanishing point. It is exactly at the level of the painter’s eye, i.e. at the level of the natural horizon. If the wall in the background were transparent and if the house were beside the sea, the sky and the sea would indeed be separated by the red line. And this would be the case whether the house is situated on the beach or on top of a rocky coastline.

The question is, then, what is special about this perspective view?

The artist has chosen a frontal view for this picture. If we are to understand the impact of this choice on the perspective we need to do something: we need to establish the plan of the room.

Here is the basic plan. What do you notice? You see that all the items of furniture are parallel to the walls. The artist, whose visual ray culminates at the red point, did not take up a position in a corner but squarely opposite the wall at the back. He could have placed himself in a corner and have his visual ray culminate at the same point. If he had done so, all the articles of furniture would have been presented to him by an angle and not by a side. So here the artist has chosen to present all the sides of the objects and the walls either at right angles to his visual ray or parallel to it, but never diagonally.

In a frontal view, the perspective is said to be “parallel”. We note also that all the lines parallel to the visual ray converge on the principal point. This time we can call it the vanishing point since it fulfils the two roles simultaneously. All the other vertical and horizontal lines, perpendicular to the visual ray, remain vertical or horizontal once placed in perspective. It’s quite simple really.

Now you have a plan and a horizon line. You know where the principal point (which is also sometimes the vanishing point) is placed. So you will now be able to build a very simple scene in which you can put your newly acquired theoretical knowledge into practice.

You are going to draw an object which is familiar to us all – a shoe box. You notice I use the simpler and more expressive word “box” rather than “regular parallelepiped”.

You want to put this box in perspective so that you can show the three dimensions in a single picture. Your drawing will unquestionably appear more solid, more constructed, if you bear in mind what you know about the viewpoint. For an accurate representation of the scene, you will start by choosing a viewpoint. You want the box to be just in front of the spectator but slightly lower than his eyes. The box will be below his horizon plane, lower than his eyes, and therefore under the horizon line.

Seen from the side, the box is placed slightly under the visual ray. So you will see the top but not the bottom, the front but not the rear.

When you look at the scene from above, this is what you see:

  • the visual ray linking the eye to the principal point passes through the median axis of the box
  • the right and left sides of the box are parallel to the visual ray
  • the front and rear sides are perpendicular to the visual ray

You have all the necessary knowledge for building up this perspective.

Lines remaining vertical or horizontal Receding lines, parallel to the visual ray The box is seen face on and is therefore in parallel perspective. In such cases, as you already know:

  • the vertical lines will stay vertical in the drawing
  • the horizontal lines perpendicular to the visual ray will stay horizontal
  • the horizontal lines parallel to the visual ray will all converge on the principal point; they recede towards the horizon hence their name “receding lines” or “vanishing lines”

Now look at the box and you will see that it corresponds perfectly to these criteria. The horizontal lines remain horizontal or recede in relation to the visual ray. The vertical lines remain vertical.

Now what would happen if we moved the box to the right or the left or even up or down? Lines remaining vertical or horizontal Receding lines, parallel to the visual ray

If you did this, one of the sides would appear and the others would disappear, but as long as these movements are not accompanied by a rotation of the box, the same rule applies.

La perspective angulaire On the other hand, if you were to rotate the box on its vertical axis, things would change considerably. Here, new rules would apply since you would be leaving the world of frontal perspective and entering the more complex realm of angular perspective. We shall in fact shortly be exploring this notion.

Lines remaining vertical or horizontal Visual rays Receding lines, parallel to the visual ray

Now take a look at these three pictures. The outline view emphasises the sides parallel to the visual ray (in turquoise blue) and the sides perpendicular to it (in yellow). As you see, the box can be centred on the visual ray or moved to one side or the other.

The visual rays traced in blue help us to understand which parts of the box will be visible on the drawing Next, here are the three possible positions for the box in elevation: above, on and below the visual ray. Three times three makes nine, so there are nine types that you are going to come across regularly.

Part 2 of the Persepctive lesson, learning to use view points and perspective

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