How to Construct a 3D / Anamorphic Perspective Chalk Drawing by Tracy Lee Stumwww.tracyleestum.com / www.streetpainting.com(with excerpts included from B. Bizarroʼs treatise on 3D projection drawing)

To Complete this lesson you will need.....

1 pad 11”x 14” drawing paperA few sheets of 8 1/2” x 11” multi-purpose paperYardstick &/or 18” rulerPencil/eraserProtractorCompass1 pad 8 1/2” x 11” vellum or tracing paper (vellum recommended)Drafting tapeScotch tape

A basic knowledge of drafting, perspective, geometry, and drawing will be helpful in this lesson.

The space we have to create our 3D chalk art is 6ʼ x 8ʼ feet. We are going to create a scale drawing of our working area and our chalk drawing. This first drawing will be a perspective drawing. Letʼs make the scale 1 unit = 1ʼ foot. The horizontal line at the bottom of the drawing (the base line) represents the bottom edge of our chalk drawing - draw that along the bottom edge of your paper. It also represents the ground that the street drawing will be placed on. The drawing area is composed of 6 units, while the distance the viewer is standing from the drawing is 5 units. (Each unit is 1ʼ foot in length.) Next we will establish the horizon line, which is parallel with the base line. The height of the viewerʼs eye (POV) from the base line determines where the horizon line falls. This vertical line on the right (X) represents a viewing height (or horizon line) of 5ʼ feet 5” inches above the ground. The horizon is always at eye level. Draw the horizon parallel to the ground and continue this line to the edge of your paper.

Figure 1A

Next extend the bottom edge of your drawing 2 units to the left as shown in Figure 1B. You may need to attach an additional sheet of paper to accomplish this. Extend the bottom edge of your drawing 5 units to the right - this represents the distance between the observer and the bottom edge of your painting (Y). Create a point of view (POV) 5 &1/2 units above the ground at this point (X). Using a long ruler or yardstick, intersect POV with the base line units to create reference points that will establish where the horizontal perspective lines will fall on the grid. (The blue lines represent the line of sight from the viewer.) Next draw the horizontal lines across the grid at the intersecting points.

Figure 1B

When you are finished, you will have a good representation of a what a 6ʼ foot x 8ʼ foot grid on the ground will look like to someone standing 5ʼ feet away from a height of 5ʼ 5”. (At this point you can go over the lines of the perspective grid in permanent ink if you like.) See Figure 1C.

Figure 1C

Next we will place an image onto this perspective grid. Draw the image (dolphin in a pool) on the perspective grid as shown in Figure 2. In this example, the image is drawn on a new sheet of vellum which is placed over our perspective grid - you will need to see both the grid and the drawing throughout the designing process. Keep your design drawing as concise as possible.

Figure 2 - Perspective Grid

Place some vellum on top of your drawing. Make it enough to create a squared version of your grid, this will become the Projection Grid. Square the grid as shown in Figure 3. It helps to draw the outer perimeter first, measure 1 unit marks along the perimeter then connect the marks. The squared grid represents 1ʼ x 1ʼ foot squares you will draw on the ground in chalk.

Figure 3 - Perspective Grid with Projection Grid placed on top.

Now, before we proceed, we should consider the viewing angle and perspective. We have already established that our observer is 3ʼ feet away from our work of art (POV) but now it is time to create an anamorphic projection point that will approximate the phenomena of parallax that occurs as a result of having two eyes.

To demonstrate parallax, hold your thumb out at arms length, look at you thumb, close one eye and observe where your thumb is in relation to some background object. Now, keep your arm extended, close the eye you are looking through and look at the same background object through the other eye. Notice how your thumb seems to shift

horizontally in relation to the fixed background point. Also notice that the greater the distance to the fixed background point, the greater the shift. Parallax projects out in a beam like a movie from a projector.

Without moving the eyes, human range of vision is about 120 degrees horizontally. Moving the eyes from side to side horizontally increases that range to about 180 degrees. Since our work will be seen on the ground and flat, we wonʼt concern ourselves with vertical range of vision. Due to parallax, our anamorphic projection point ends up in front of our POV and not directly on it. Using a protractor and a compass, we will create an anamorphic projection point for our drawing similar to the one shown in the example in Figure 4. The grid size in figure 4 is different from ours but the principle still applies. A horizontal line is drawn at least 5 grid units long intersecting POV (figure 4). An arc is drawn with radius 2.4” inches. Marked are 30 degree points along the arc at the West and East ends. The points are connected. The intersection of drawing vertical center and 30 degree horizontal is the projection point (PP).

Figure 4

The illusion of 3D in chalk art (or any 2-dimensional art form) is achieved by intentionally distorting images but the method of distortion is an exact science and not guesswork. The distance of POV from the grid base line is equal to the distance of the viewer from the base line, in this case, 3 units or 3ʼ feet. Lines are drawn radiating out from the projection point (PP), not the POV. The lines are also used as spacial reference points as they intersect grid lines.

As a step by step guide to find PP, referring to Figure 4 above, follow the steps below:

1. Place the POV 3 units along the vertical center of the drawing from the bottom edge of the drawing remembering that our photo will be taken 5ʼ feet away from the chalk drawing edge.

2. Draw a horizontal line through POV at a right angle to drawing center. Make the line 5 units long.

3. Using a compass, draw an arc slightly under 2.5 units radius4. Using a protractor, find the 30 degree points on the arc on the East and West ends of

the arc.5. Intersect a line from 30 degree points on the East and West ends of the arc with

vertical center of the drawing, mark projection point. We now have our anamorphic projection point. This point will be used to project key elements in our perspective drawing onto our squared grid just like the example given above.

Accuracy is important at this stage. Take your time and make sure all your measurements are correct. Accuracy of drawing and measurement are key to a successful 3D illusion.

Figure 5

Using a yardstick and the projection point, find key elements in the perspective drawing (green lines), readily identifiable reference points, and project them onto the squared Projection Grid (as shown in the red lines). Locate portions of the design that intersect grid lines and make them correspond to the squared grid. For example, the eye on the dolphin is used as key reference point for projection (Figure 6). I used the blue lines to indicate these points. The grid is used to tell where the major points should end. Imagine what a movie would look like if instead of the screen being perpendicular to the projector, if it were tilted at an angle away from the audience. The image on the screen would appear to become more distorted as the screen tilts away from the audience. That is how you have to draw in order to distort the image to compensate for the unusual viewing angle. Less distortion close to the audience, more distortion away from the audience. The finished grid with the distorted dolphin image is called the Projection Grid.

Figure 6Projection Grid(reference drawing)

When working on transferring the drawing to the projection grid, use the numbered squares as an additional guide when placing key aspects of the design. It will feel very unnatural to draw like his at first, but after you have done a few, you will feel more natural to draw this way the more 3D chalk pieces you do.

When you are complete with the basic lay-out, the projection grid is the reference you will work from when making your chalk painting. Start with something relatively simple to build up your confidence when working with distorted images. You will lay out the Projection Grid on the ground exactly as in your reference drawing, and using this as a map, place all the appropriate lines where they are indicated on your reference drawing.

You may also find that you can create the projection grid with a computer program - however, while this may be a time efficient approach, I think it is always important for the artist to understand the principles behind the techniques he employs, hence this document!

Some additional notes: When you are ready to photograph your finished chalk piece, mark a point on the ground that corresponds to the POV in your design (5ʼ feet away in our example). Shoot from the POV point, not the PP point. (The projection point is ALWAYS in front of the POV.) Add a person interacting with your chalk piece to make the final photo more authentic and amazing!

You may also want to use your set up digital camera as a means to check the progress of your work as you proceed. Make any visual adjustments as seen necessary through the camera lens. I often find that while my drawing is accurate, there may be some elements that when seen through the lens, appear to be slightly off. Use your artistic intuition to improvise as needed!

It is important to note that holes in the ground, such as the one in this image, are drawn circular on our squared grid. Any openings in the ground of a 3D chalk piece are drawn circular. Perspective creates the oval shape that will be seen. Likewise, if you want something to appear circular in your painting, a sphere for example, you will need to draw it in an elongated oval shape - the camera lens will then corrects it into a sphere when shot from the correct POV.

And finally, proper lighting and shading of your image will create a much more believable illusion. You may want to search for a reference that has the correct lighting and colorization indicated to help with this.

Suggested additional reading:Andrea del Pozzo - ʻPerspective in Architecture and PaintingʼJurgis Baltrusaitis - ʻAnamorphosesʼ

Website on Modular Perspective for Street Painting:www.perspectivegeometry.com

Examples of 3D chalk art in 3D / Anamorphic Perspective by Tracy Lee Stum