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The Metrics of Space: Tactical Level Design

September 4, 2012 Article Start Page 1 of 5 Next
 

What makes good level design? PhD and educator McMillan -- who's worked with Ubisoft to create a curriculum for game design -- examines how point of view effects players, showcasing a variety of gameplay scenarios which show different tactical choices players may be confronted with.

There are various means of understanding how the perception of 3D spaces in games changes the player's emotional state.

One methodology used in level design is that of architectural perspective -- the relationship of the player and the spaces that they occupy at any given time. Many implementations of this approach do not consider more dynamic relationships involving the player, other agents and the environment.

This article looks at dynamic relationships within 3D space in order to understand how we can use dynamic objects in conjunction with level geometry to adjust game difficulty and the player's emotional state. To achieve this goal, this article will take the novel approach of evaluating the tactics of players in the context of modern, 3D FPS games.

Objectives:

  • An understanding of how we can tailor the difficulty level of virtual spaces in games through a better understanding of what makes 3D FPS levels more or less difficult.
  • A look at how difficulty ramping can be achieved using a number of different approaches.

The Metrics of Space

In order to take a rational approach to the design of 3D game spaces, we need to identify a number of metrics. The primary metric that alters difficulty is player line of sight. The greater a player's line of sight, the more able they are to plan ahead and think strategically about the game world.

Greater line of sight also allows the possibilities for a larger amount of tactical options, as the player will have more time to plan and also a greater situational awareness. On the other hand, reducing the player's line of sight will result in disadvantaging the player, as they will have less situational awareness and less time to act to certain problems.

I must point out that this observation is in relation primarily to the FPS genre. If we were to phrase this in broader terms, we could make the same conclusions by citing a player's "situational awareness"; however, as this article is level design-centric, I will instead dissect this notion of line of sight.

We can measure line of sight using two key principles: the angle created by geometric field of view (GFOV) as well as the fidelity of graphical resolution, which will tell us how far the player can accurately see. (Figure 1)


Figure 1

Geometric Field of View & Display Field of View

When dealing with the rendering of 3D spaces, we are primarily concerned with the geometric field of view (Figure 2). The GFO is the most commonly discussed type of field of view metric, as this field of view is that of the player's camera. The width is represented as an angle that measures the horizontal span of the frustum. The far clipping plane is the point at which the game engine stops rendering. We sometime hear this referred to as "draw distance". Complex rendering systems will express this element of visual acuity in "arc minutes."


Figure 2

Less discussed is the concept of display field of view, or DFOV (Figure 3). This is the field of view dictated by the player's distance to display and the size of the display that they are playing the game with. Interestingly, the DFOV plays an exceedingly important role in the navigation and subsequent difficulty of 3D space, but only for female gamers. Research conducted by Tan, Czerwinski, and Robertson (2006) suggests that female players have the most to gain when the DFOV and GFOV angle is a 1:1 relationship. Interestingly, males seem to be far less affected in their navigation of 3D spaces when this relationship is changed, even dramatically.


Figure 3

Portals & Occluders, and Line of Sight

A portal is any game device that allows for greater-than-usual line of sight. We could consider a gantry that surrounds an upper level of a factory level as a type of portal, as the player is able to use the open floor plan to gain a view of the floor beneath them (Figure 4). This is why we often see players taking the "high ground" in a tactical scenario, as the height elevation allows for a greater situational awareness as opposed to if the player remained on the lower parts of the map. Windows and doorways also constitute portals within game levels.


Figure 4

Any type of weapon of game object that allows the player to have greater control over their view of the virtual world is extremely powerful. Weapons like the sniper rifle, which its ability to increase line of sight, are extremely powerful as a consequence. These powerful abilities, however, are usually compromised in some way. The sniper rifle, although giving the player greater line of sight, will always reduce the player's GFOV (Figure 5). Or the homing rocket used in Unreal Tournament will leave the player exposed to attack whilst in use.


Figure 5

Occluders can also modify graphical fidelity, and subsequently limit peripheral vision, or the player's view distance. The flashlight used in Doom 3 is one of the best examples of an occluding device that does both of these things (Figure 6).


Figure 6

The flashlight technique is also interesting from a spatial perspective, as it makes small spaces seem artificially larger, and encourages the player to explore parts of a room or level that they wouldn't otherwise do if it were fully lit. On face value, Doom 3's levels have an extremely linear design when compared to the franchise's earlier titles; however, the player is kept in the smaller spaces longer, as the use of occlusion means that they need to spend longer gaining a situational awareness of each room.

The "noise" effect used in Silent Hill 2 (Figure 7) is also another alternative occluding device, used to reduce the player's line of sight and subsequently make them feel more cautious. It is also important to note that effects like this often serve an important technical purpose, as they reduce the draw distance required in large, open environments whilst also giving the illusion that the environment is larger than what it seems. We often see simulated weather effects such rain, fog and simulated snow used to achieve a similar goal.


Figure 7

In the context of games, level designers can use the principle of portals and occluders to adjust the difficulty of a game's virtual space. Figure 8 demonstrate the difference in difficulty associated with using occlusion. In the example of the left, the player has a significantly heightened sense of situational awareness, as they can see through the walls. This will mean that they will be on the "front foot" when it comes to engaging any enemies.


Figure 8

In the example on the right, occlusion is used to limit the player's situational awareness. By doing so, the player will undergo moments of anxiety when exploring new spaces, as they will need to quickly familiarize themselves with the layout of the space so that they can plan strategically for a number of possibilities. Although there are many psychological outcomes from these mechanisms, in the context of this article, we are dealing primarily with occluders and portals as a function of difficulty ramping using 3D spaces.


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