Presentations are traditionally two dimensional environments, but with the proliferation of 3D TVs, projectors, and laptops, the world of presentations will probably start to embrace 3D, but will it be more successful, and longer lasting than the faltering steps of 3D in cinemas?

Well, unlike the cinema, which is usually about entertainment, presentations are about informing the audience, and with 3D, presenters have the potential to be able to communication even more information. There are already additional plug-ins that can be used to create 3D effects in PowerPoint to take advantage of these new displays, but if you don’t have one, then it’s no good. Instead, can you take advantage of the extra dimension with your current set up of PowerPoint and a standard screen? What are the things that you need to consider?

Depth & size perception

First, let’s look at how we actually perceive depth and size, and so benefit from the extra information that an additional dimension can provide. A key feature of visual perception is the ability to transform the two dimensional retinal image into the perception of a three dimensional world, seen in depth.

There are three key cues for depth and size perception:

  • Monocular cues require the use of only one eye, although they can readily be seen when both eyes are open.
  • Binocular cues involve the use of both eyes together.
  • Oculomotor cues are kinaesthetic cues that depend upon the sensations of muscular contractions of the muscles around the eyes.

Monocular cues can be used in 2D situations, such as a presentation, whereas binocular cues and oculomotor cues are used for 3D, real world stimuli. You therefore need to focus on these 2D monocular cues to achieve the effects that you need.

In the real world, objects are three dimensional; however there are many instances where three dimensional information or objects need to be conveyed in only two dimensions. Monocular cues to depth are often called pictorial cues as they are used by artists trying to create the impression of three dimensional scenes on two dimensional canvasses. There are several different monocular cues to depth that you could use to create the perception of depth and size.

Linear perspective is created by parallel lines pointing directly away which seem progressively closer as they recede into the distance e.g. the edges of a motorway. This convergence of the lines creates a powerful impression of depth in a two dimensional drawing.

Aerial perspective is related to linear perspective. When light travels through the atmosphere, it becomes scattered, making distant objects seem hazy. You can mimick the effect of aerial perspective by reducing the contrast of features within an image, leading these features to appear more distant.

Most objects e.g. carpets, or cobbled streets, possess texture and textured objects slanting away from the observer have a texture gradient. This texture gradient causes objects further away to appear less detailed and closer together than they would do closer up.

Interposition is an effect whereby nearer objects hide part of a more distant object from view. The strength of this cue can be seen in Kaniza’s (1976) illusory square, which gives a strong impression of a square in front of four circles, even though many of the contours of the square are missing.

Flat, two dimensional surfaces do not cast shadows and so the presence of shading indicates the presence of a three dimensional object. If you use the shading and bevel functions native to PowerPoint 2007 and above to illuminate objects in different ways, you can give the impression of objects being either concave or convex, despite all the objects actually being the same.

If the size of an object is known, then its retinal image can be used to provide an accurate estimate of distance, but if the object is not a familiar size, then distance judgements can be inaccurate. Ittelson (1951) had observers look at three playing cards (half size, regular size, double size) through a peephole to force monocular vision and eliminate depth cues other than familiar size and found that the observers assumed that all three cards were the same size, and judged their distances to be nearer or further away, depending upon the actual size of the card.

Motion parallax refers to movement of an object relative to the viewer, with the movement being greater for the closer of two objects e.g. if looking through the window of a moving train, the apparent speed of objects passing by seems faster, the nearer that they are to the observer. Motion parallax can generate depth information in the absence of all other depth dues, and can be achieved using different layers and speeds of motion paths in PowerPoint.

Size constancy

Despite having several different types of monocular cue to infer a third physical dimension, the visual perception of objects is still based on the pattern and wavelength of light falling on the retina in the eye, giving a retinal image.

Objects are perceived to have a given size, regardless of the size of retinal image, based on the object’s relative position in its environment, including different layers and perspective. It is possible to use layers and perspective to make objects appear to be different sizes. However, familiar objects have a known size and are thought of as that size, despite the size of the retinal image.

If an object is closer to you, then the retinal size may increase, but the perceived size will stay the same. Likewise, if the object is further away, a smaller retinal image will not change the perception of actual size. So if an image of a banana is projected, it is always perceived to be 20cm long and not 4m, despite the size of the retinal image suggesting an increase in size

However, if the object is with other objects in the same layer, then the relative size of these objects can be used to provide fine detail judgement of actual size, which means that you should always try to include some level of comparison to give real depth to your presentations, and ensure that size is correctly perceived.

One example of how size constancy and the use of layers and perspective can make objects appear to be different sizes is demonstrated in an Ames Room. Jen is smaller than Ed, but not by much, yet in an Ames Room, she can either look much smaller, or much larger. This affect is achieved by playing with sizes, layers, and perspective, and relies upon the viewer being in a specific location.

Ames Room 1

Ames Room 2

So, what’s the secret behind this effect? By having a distorted room and viewing from the right angle, the Ames Room can trick perception that the room is not distorted, making the individuals or objects inside it appear much smaller or larger than reality.

These types of effects can also be achieved by manipulating the fact that your audience is always in the same position during a presentation, and using size, layers, and perspective to achieve the desired effect.

Multi-dimensional presenting

You can employ a number of different techniques to create the illusion of 3D in your presentations, and so you can increase the amount of information that you can convey, and often ensure that the information is in a form that is more relevant to audience members, helping them to understand concepts more quickly and more easily.

In fact, why stop at just 3D? With the ability to change the content of a slide, using animations over time, a further dimension is available to presenters and audiences, giving you what are now relatively common four dimensional presentations – searching Google for ‘4D presentation’ provides you with 11 million results. Imagine the possibilities and get to work, starting with a few tips on creating 3D effects in PowerPoint.

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Richard Goring

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