Believability Notes

Chapter 1 Introduction

1.1 What is “believable”  ?

The meaning of “believable” is something that we consider to be true, or a person who we believe to be trustworthy. Believable can also be understood as “suspension of disbelief”. This can be defined as the ability to overcome the observer’s doubts that the subject presented is real or some form of truth. A common way to achieve this is to enable the observer to relate to the subject of the work on a personal level. In the artistic domain, examples of believable subjects can be a character in a play, the plot of a novel or an animated figure.

1.2 Suspension of Disbelief

Suspending disbelief has been the primary endeavour in character-based arts across all mediums, from sculptures and painting to theatre, over writing to radio and up to television and video games.

Throughout the evolution of media our ability to emulate reality in our creations, has become more refined. With this increasing degree of realism and fidelity, suspending disbelief in the viewer appears to become easier to achieve. Yet when we compare expressive media according to how much “work” is left to the observer’s imagination, we see that it has become more difficult. To bring across the “Gestalt” of a character (expressions, body language, choice of actions etc.) in a modern medium, requires the artist to pay attention to a much greater set of details and nuances, than was required in a less explicit, more abstract medium. If the artist does not cater to these details, the work will be less believable.

A medium like written text can “use” the reader’s imagination to fill in the details, while an inherently explicit medium like interactive animation is posed against closer scrutiny for lacking detail.

For example if a writer writes, “There is a room, it is dark”, the reader will imagine a dark room as he knows it from experience. On the other hand if a painter draws a black square and says “This is a dark room”, the observer is likely not to believe this, unless the painter considers and includes the details of the room: the dimension of the room, the perspective of the eye. The painter also has to put light into the dark room to make these properties visible.

–possibly describe the difference between believability and realism–

It could be said that Leonardo Da Vinci, who took around 5 years to create his masterpiece, the Mona Lisa, would have struggled even more to produce an animation of the same intrinsic quality– let alone an interactive animation. The medium of painting, with all its expressional limits allowed him to focus on the characteristic nuances that make it a masterpiece. A 10 second animation with 15 images a second, while retaining all that detail, would have taken a lifetime (~750 years, actually).

1.3 Details

Description of what those details are. Based mainly on thesis by Loyall and Disney and the Stanislavski.

While realism applies to the generalities, the physics of the world, believability rests in the nuances. Before I describe what these are, let me talk about a problem that occurs with increased realism, especially with human characters.

1.4 The Uncanny Valley Effect

For creators of believable human-like characters the Uncanny Valley concept has been a problematic issue. Originally the term was coined by psychologists Ernst Jentsch in 1906 (Jentsch 1997) and Sigmund Freud in 1919. The theory states that if a realistic human-like figure comes too close to looking like a real human being, an observer will suddenly switch from an empathetic, to a repulsed response. (White, McKay et al. 2007) state that this effect can be observed for static or moving images, figurines and robots and doesn’t just apply to the visual impression (looking like a human), but also to movement (moving like a human).

The movie “Final Fantasy: The Spirits Within” (Sakaguchi and Sakakibara 2001) is a good example. It featured characters that looked very realistic when static (Figure 1). The artists considered almost all the criteria for physical photo-realism, such as light reflections and refractions in the skin and eyes, texture, moisture and natural colours. Yet when seen in motion, the animated characters often elicit a feeling of discomfort, a feeling that somehow these characters look less like living breathing people and more like walking, talking corpses.

A way to avoid the Uncanny valley altogether is by avoiding realism. Non-realistic anthropomorphic characters, such as Disney’s Donald Duck do not run the risk of seeming too human-like, yet can be used to transport believable human traits – a method also used in Aesop’s Fables.

My work aims to show a new approach to creating interactive believable characters. My focus is not on creating human-like figures.

1.6 Key Related Research Projects

1.6.1 Oz Project and HAP Architecture by Joseph Bates and Bryan Loyall at CMU

I would not say that the agents created with HAP are autonomous. The agents have no ability to correct their behaviour and therefore fall under Searl’s Chinese room argument about weak AI. HAP creates an interactive narrative with additional, implied rules and dynamics that the author might add unintentionally while creating the agent’s rules. The agent is therefore not an interactive personality.

Jentsch, E. (1997). “On the psychology of the uncanny (1906).” Angelaki: Journal of Theoretical Humanities 2(1): 7-16.

Sakaguchi, H. and M. Sakakibara (2001). Final Fantasy: The Spirits Within. Japan.

White, G., L. McKay, et al. (2007). “{Motion and the uncanny valley}.” J. Vis. 7(9): 477-477.

Plants vs. Zombies Review

This is a summary of the issues we discussed during the Sussex Games Reading Group meeting on the 26th of June 2009.

Its a review of “Plants vs. Zombies” by PopCap:

1. Could have become harder quicker
2. After playing the Demo you couldn’t port your progress into the Full version
a. EA did this with the Sim and Spore Creature designer
3. Timed Demo gives impression that game is very short
4. Difficulty spikes – why does it get easier after being hard? –> What am I doing wrong?
5. Certain items are much more useful than others
6. Some of the plant descriptions could have been more informative for the difficult levels (optional plant set hint).
7. Half way through a level some plants can become useless (mainly because you don’t want to waste your slots for them).
8. Usability: Can’t move plants around in slots, to re-order them you have to empty the slots
9. Usability: Zen garden has problem when moving plant. You can accidently click and move the plant to the wrong point
10. Usability: Zen garden – you can’t swap plants, only move them to a empty slot.
11. Tree of knowledge doesn’t give any good hints, basically useless. Promises reward. World of goo’s tower is much better.
12. Golden watering can doesn’t help much.
13. Usability: Golden Watering can doesn’t show exactly what it waters.
14. The almanac didn’t have consistency when it came to the stats
15. The bomb plants are very similar and their different strengths are not signposted very well.


Do you sometimes find yourself getting worse at writing? I don’t know if it’s down to burnout, or whatever else – but I was just reading some of the things I wrote a year ago and I must say, I wish I was that clear about things now. Isn’t research supposed to clear things up? It seems to me that right now I feel like I am just starting, whereas when I started I had a pretty clear picture.
Specifically, I am currently trying to write my literature reviews for my Transfer from MPhil to PhD and I’m finding it so difficult to summarize the papers I’m reading that I’m resorting to “how to write a literature review” guides. Then I looked back at the lit reviews I had done for my proposal (yes, that was before my research) and they are great! They summarize all the key points, compare and contrast them to my project and cross reference the most important works! It’s ridiculous!

Natal and VR

Microsoft presented project NATAL at E3 this year. This has rekindled my interest in the matching VR display problem (we want that holodeck!). Anyway, my main interest is in multiview displays or panoramagrams.

The idea is that a display presents multiple images at different angles, this generating a different image for each eye from whichever angle you look at it – generating stereoscopic image.

I think the future solution to this will be something like nano-pixels, where a group of light sources (lED or something smaller) form a half sphere. The seperate rays are deliniated by tiny tiny tubes (maybe not quite nano) that prevent the eye from seeing the others from a given angle.

This, together with a motion detection tech similar to NATAL and a VR setup like the CAVE would pretty much check all the boxes for a holodeck, although we still cant hold project objects onto our hand that way (we’d need a display on our hands with the current solution, which seems infeasable). So it’s not perfect, but definately a step forward as it works without periferals and with multiple participants: both the motion detection and the multiview screen techs are user-number independent.