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Tertiary Motion and Vector Consistency During Gameplay
by Altug Isigan on 02/01/10 12:15:00 pm

The following blog post, unless otherwise noted, was written by a member of Gamasutra’s community.
The thoughts and opinions expressed are those of the writer and not Gamasutra or its parent company.

 

Video Games: A Natural Enemy to Tertiary Motion?

Film is often hailed as the art of montage or editing, which is the re-arrangement of recorded events. Montage or editing creates the type of motion that we call tertiary motion (or sequence motion). In other words, tertiary morion is the visual development of a screen event based on shot variation, especially through the use of cuts. Herein lies one of the bigger differences between films and video games. While in most films, tertiary motion is at the heart of the aesthetic experience, in games we rarely see tertiary motion during gameplay because it makes control difficult. Games are rather based on a combination of secondary motion (camera movement) and primary motion (object movement) [1].  

Principal Motions in Video Games

Despite the huge technical developments in the history of video games  tertiary motion could not really break through as a major form of ludic narration. Even in very cinematic experiences like God of War, the use of tertiary motion is very limited.  The reason for this is the difference in the positioning of the  player. The players participation requires a feel of  control over her movement and decisions, which is seemingly not getting along well with tertiary motion types (because basically these appear to be the result of someone else's decision and destroy continuity in agency).

Let's classify games according to the types of cinematic motion they utilize:

Primary Motion Games

The typical action-arcade game of the 70s would be a game based on primary motion (object motion). Like theatre so to say: we have a static frame or a ’stage’ and objects move within it, or in and out of it: Pong. Space Invaders, Centipede can be given as examples. Tertiary motion (or sequence motion) usually would be only observable at the beginning of the game, during transitions between levels, and at the end of the game (but not during gameplay). For example, the game would cut or fade to another static screen, like the Highscores screen. A few games that broke this rule come in mind, but they rather seem to be rare: Asteriods used cuts (tertiary motion) during gameplay, which functioned as a jump to another ’slide’ when your spaceship travelled out of the previous one. Joust worked the same way. A genre that seemed more suitable for this kind of Tertiary motion was the adventure game, because of it’s sequential progress of puzzles and the progress from “room to room” of which each one was a different slide.

Secondary Motion Games

With the introduction of side-scrollers, secondary motion (a moving camera during gameplay) became an essential part of video games. Not only objects moved, but also the camera. Again tertiary motion cannot be found much during gameplay, but rather at the beginning and ends, or inbetween levels. In such games secondary motion is usually limited along the x and y-axis. The game scrolls to the left or the right, or up and down. In some games you can also zoom into events, but this is not to be confused with continuous motion along the z-axis. A notable genre in which secondary motion along the z-axis is fundamental is the car an air plane simulation genre. Games like Pitstop and some early Star Wars games come in mind.

Advanced Secondary Motion: 3D Games

When 3D graphics arrived, we were now able to move the virtual camera continously along the z-axis, and into whatever other direction we want; which gave incredible depth to the games, but actually still none of these games are based on tertiary motion. Usually at the beginning of an FPS, we are “discovered” by an NPC, who speaks while directly looking into the camera, thereby establishing the “subjective camera” that represents us, and after that, we move this “subjective” camera (secondary motion) around and engage with enemies that come within our range-of-view (enemy being examples of primary motion).

The Problem of Vector Consistency During Gameplay

One of the important problems that is caused by tertiary motion during gameplay is that of vector inconsistency. As the camera quickly switches from one position to another, a move which is often referred to as jogging, it is possible that the player loses the feeling of control and has difficulties in maintaining directional continuity. Since immersion requires the illusion of agency, and agency is based on a feeling of control over actions, the resulting disorientation will pull the player out of the depths of her experience. One reason for tertiary motion being so distracting is that it happens often based on a decision of the game AI, and not the character. It is normal that any player would perceive this as an interference to gameplay and a loss over agency. This problematic situation requires tertiary motion to be build very carefully into gameplay. Vector Consistency is one of the concepts that can help us in this regard.

Indeed, one of the things that the camera use in games obeys to, seems to be vector consistency. In many games the camera is locked onto the player character (based on certain parametres like distance, angle etc, which do not change during gameplay). Vector consistency is maintained during the whole process, even if we have very lively secondary motion (like in FPS or TPS games where the player constantly moves around in a 3D World).

How Is Vector Consistency Ensured in Video Games?

Vector consistency is maintained in a few simple ways:

1) Either the camera frame is identified with our gaze (which makes it a subjective camera), or;

2) the camera follows the player’s avatar in a pre-set way, visually assisting the player in maintaining the feel of agency.

In both cases, the camera motion is glued to the player or his representation, rarely ever leaving this locked position. Despite all the action, there is no visual jumping that confuses the player. This is quite different from what happens in film. In film you rarely see scenes with cameras locked onto the subject for a long time, and if, then these scenes often aim for the creation of a specific meaning [2].

The Challenge of Interactive Media: Vector Consistency during Tertiary Motion

However, despite the cam-lock in games, slight cam-moves are used frequently. Usually their aim is to add depth to gameplay or give comfort to the player by providing cam adjustment to the conditions. For example the cam drags behind for a few seconds when you accelerate your car in Need for Speed, which helps you to feel the energy under the hub. In some shooters on the other hand (for example Full Spectrum Warrior) the camera strafes to the right or to the left to gain more field-of-vision for the player when he rests close to a wall corner that hinders sight. However these are secondary motions in accordance with the active vector, and often contribute to the experience, rather than taking away from it. The question is how tertiary motions like cuts should be built into gameplay without making the feel of control suffer.

The 30 Degrees Rule: A solution for video games?

It has been said that a cut that changes the camera-angle less than 30 degrees confuses the film spectator, because the change in the angle usually feels too insignificant as to cause a difference in the situation it narrates. Therefore the spectator doesn’t get what reaction is expected from him and wonders why the cut actually happened. On the other hand, in games, the player gets confused when during ongoing motion in gameplay the angle changes too radically, because the player loses connection to the motion vector he believes to “ride” on in that very moment. It could be interesting to conduct a research on how players feel in regard to different angles. When do they feel the change in the angle takes away control from them? When is a change in the angle so insignificant that it gets them confused on what they were expected to think or feel? 

Cutting along the Z-Axis

Probably the best way to avoid confusion during cuts is to select a frame that is located onto the direction of the motion vector that the player holds. If this is primarily the z-axis, then our cut should jump anywhere along the z-axis, preserving the initial angle. Cuts should remain in a spectrum that ranges from Long-shot to close-up’s, not playing with the angle at all.

Moving the Camera when the Player stands still

Also, it could be claimed that the player will tolerate more tertiary motion if she doesn’t move at the moment of the switch, because there is a stable frame of reference that puts the camera motion in context, without causing confusion.

The Jogging Technique
One way to include more tertiary motion in games (and as a result, having them more ‘cinematic’ in style) would be to emphasize the outcome of small events through quick, short-lasting camera position switches, known as “jogging”.

Assume that in an ambush, I fire a bullet to an enemy at a distance. The camera could quick-jump to a position that shows me with a close up the impact of the bullet I just fired, but only for half-a-second, long enough to tell me that I hit or was very close to hit. (actually any game with a sniper-mode should have the basis for such a camera-algorithm already built into the game engine).In other words, the AI would respond by switching cam position if my bullet ‘lands’ within a certain range of the target, including the target itself.

The quick switch to a close shot of the player’s attempt to hit the enemy, could be a way to get her deeper involved with her objective, to hit the enemy. Examples of jogging can be seen in the Need For Speed series, in which the camera jogs to positions in which we see our cars flying through the air in slow motion from the most spectacular angles. But once the car touches the ground again, we are back in “normal” mode.

Jogging with Caution

It could be annoying for the player to see the cam switching too often, because basically it happens not as the result of a player decision. Also the interaction between game mechanics and various AI-controlled  features can cause problems: for example it would be a huge task to get AI-contolled jogging to work proper when a player uses an automatic guns in a FPS: imagine the camera jogging for every bullet that lands within the target territory! That would be several jogs per second. Such tertiary motion features would need to be tested in a variety of situations and probably presented as features that can be turned off if the player doesn’t feel confortable with the jogs.

One rule with jogging is that it should be done at locations or in situations in which the player has time to adapt to the return to normal gameplay mode after the jogging; meaning that in no way she should lose an advantage as a result of the absence of control during the jog. Going back to the shooting example, a player probably would get angry with the game if she should discover that she was killed while the camera was jogging and the player had no control over the event. In short: Jogging should be meaningful in both aesthetic and narrative/dramatic terms, AND it should prevent all actions that could damage the players status during jogging from happening.

AI That Serves the Intention of the Player is Key

The problem of visual and vectoral continuity is less a problem when the player herself decides to change the angle and moves the camera deliberately, because then the player is fully aware of the intention behind the camera move (which simply is her own intention). It becomes rather problematic when the design of the cam algorithm is not really able to follow the basic player intentions that emerge during gameplay. The player continually will experience a lack of correspondence and feel that the game is difficult to control. Even if the cam design is ok, a player atill can mess up things and lose sight (or orientation), so some games provide this cool button that resets your view to the “standart” camera position of the game. This means you can re-build your feeling of continuity, and that is the reasons why it feels so much home, so much safe to be able to do this.

Is it the Turn of Tertiary Motion?

My direct answer is no. But achievements in both AI and gameplay literacy (yes, it is very important what gamers know about "reading" games) can change that. 

It can be said that even today, in times in which we can play as cinematic games as God of War, that sceen events in most of the video games genres are articulated differently from those in film.  In video games thing become problematic when tertiary motion is involved. In most games, events are placed along the pathway of one long uncut shot, seen through a single camera that continously travels through the virtual environment. An important part of storytelling and dramatization is done with the help of graphication devices such as HUD-displays and other visual elements that blend in during gameplay.. and sound of course.

These differences require filmic writing approaches in game development to be reviewed. Not necessarily in terms of the basic principles of drama  but in regard to proper visual narration. While writing, the writer maybe needs to be aware that the video game “director” cannot make as heavy use of tertiary motion as the film director can. The writer must understand that writing for games requires player control to be considered while she writes how the scene unfolds.

Notes

[1] This is also the main reason why game-trailers shouldn’t be seen as promises regarding gameplay. A trailer is something to watch, not to control; usually it is built on an amount of tertiary motion that the game would not be able to support during gameplay for reasons of player control.

[2] One memorable exception is the film Lady in the Lake, fully shot in first person perspective. Wikipedia quotes a The New York Times film critic writing the following: "In making the camera an active participant, rather than an off-side reporter, Mr. Montgomery has, however, failed to exploit the full possibilities suggested by this unusual technique. For after a few minutes of seeing a hand reaching toward a door knob, or lighting a cigarette or lifting a glass, or a door moving toward you as though it might come right out of the screen the novelty begins to wear thin."

 

References

http://en.wikipedia.org/wiki/Lady_in_the_Lake

 

This article has been published earlier on my game blog The Ludosphere.


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Altug Isigan
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Hi Bob,



sorry, I completely missed this comment and I'm very late with my response.



You put those two approaches very well. In this article, I try to describe a way to deal with player control issues for both approaches. It's not a well written article I must admit, but it helped me to formulate some basic ideas. Spectacle versus control remains the important challenge in game design, and the more games acquire a cinematic character, the trickier will it be to make control convenient for the player.



I do not exactly agree with the point that a shift to more complex (cinema-like) visualization necessarily results in gameplay automatically suffering from it. It rather suffers when the chosen visual presentation style is in conflict with the player's need for control over her actions. There is no formula to get this into balance, each game project needs its own questions to be answered in that regard. I believe that games like God of War show us that is isn't impossible, and that a highly active camera can enhance gameplay, rather than being in conflict with it. But then, tertiary motion consists of a different set of visual style elements and I think it's exactly this set of style elements which hasn't been explored significantly yet by game developers. My article is an attempt to put the issue in context and thow up a few questions and answers.


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