Post by a Chunk on May 30, 2019 15:31:18 GMT
The Metrics of Space: Tactical Level Design
by Luke McMillan
Read this article at our new site HERE: www.nextleveldesign.org/index.php?/featured-content/articles/the-metrics-of-space-tactical-level-design-r95/
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
Figure 6
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
Figure 8
Secondary Metric: The Ability to Move, and Possibilities for Movement
When dealing with the rational design of 3D spaces, the designer needs to be aware of how control interfaces can make movement in a 3D space more or less difficult.
Figure 9
The use of space needs to be analyzed with the addition of the primary metric, line of sight.
Even though a large space may offer the player greater amounts of opportunity, a limited line of sight will override any advantage that the space brings with it, and this is similar to the use of the flashlight in Doom 3. (Figure 9)
Alternatively, when the player's view frustum is sufficiently large enough in comparison to the virtual space, they will be the most empowered (Figure 10). A simple way of thinking about the combination of these two elements is to consider that the size of a game space is always filtered through the player's view frustum; hence, in terms of a hierarchy of difficulty metrics, virtual space will always be secondary, as the world is ultimately communicated to the player via the camera system.
Figure 10
Approach Vectors
Virtual space is a trade-off for the player between possibility for movement and possibility for ambush. The easiest way to understand this trade-off is by considering the relationship of line of sight, virtual space, and enemy approach vectors.
There are three ways of understanding how approach vectors affect the game's difficulty. Difficulty of approach vectors is dictated by whether an enemy occupies the players existing view frustum, whether they have to move view frustum, or if they have to move view frustum and change world position to engage.
Easiest Approach Vectors: Those which the player can see in their immediate view frustum without the need to adjust their position or view. (Figure 11)
Figure 11
Figure 12
Most Difficult: Any approach vector that requires the player to shift their view the most from its current position.
Figure 13
Player Psychology: Correction Cycles
Humans are excellent "guesstimaters." We tend to iteratively guesstimate our way to the solution of problem by continually guessing, observing, and correcting. Imagine you are reaching out for your cup of coffee. You will move your hand, observe its new position, and then update the amount of movement required to meet with the target. This will happen many times per second until you reach your goal. (Figure 14) (This is akin to Steve Swink's "delicious cupcake" example in Game Feel.)
Figure 14
Figure 14 is an example of our guesstimation process when honing in on a static target. The large red triangles represent the margin for error in any guesstimation phase; the larger the triangle, the more room for error in that guesstimation step.
As we hone in on our target via movement, observation, and correction (update), we gradually reduce our margin of error. However, if an object continues to move, then the amount of possibilities will not reduce in a linear fashion, like Figure 14 suggests.
To give another example, let's assume that the player is undertaking the same process of move, observe, update for a static object -- say they are trying to adjust their crosshair so it is over a target. They will gradually move the crosshair until the margin of error becomes lower and lower via this process of refinement.
Now, imagine of the target suddenly reacts to the player and attempts to evade them via strafing away (Figure 15). The player will now need to significantly update their process of guesstimation, bringing more possibilities, and hence a greater margin for error, until they eventually hone in on the enemy again.
Figure 15
Although open spaces open up the possibility for the player to be flanked or approached from many more approach vectors by enemies, more open spaces also allow the opportunity for evasive maneuvers by the player.
In Figure 16, the player has the advantage, as there are more evasion vectors than enemy approach vectors. In a previous article where I dealt with the notion of compression and funnelling, I refer to these vectors as "expansion vectors" -- an element which can alleviate the tension caused by compression via enemy encroachment on the player.
Figure 16
Figure 17
Figure 18
Figure 19
Now that we have an understanding of the essential metrics and player psychology, we can now look at how level geometry begins to modify these relationships from both a difficulty perspective as well as an emotional perspective.
Figure 20 is a simple depiction of how level geometry begins to modify the player's the emotional state and strategy by affecting the view frustum. Frame 1 of Figure 20 shows an artificial representation of the player's view frustum, whilst frame 2 depicts the actual view frustum after occlusion.
Figure 20
Figure 21
In this example, the player will need to rush into unknown space in order to engage the enemy. They will be hesitant to do this, as it will require changes to GFOV and world position in order to engage. Further to this, as the room has been occluded, they will have not situational awareness in this environment -- they may even believe that they are moving into another tight hallway.
There is, however, an upside; confined spaces are sometimes beneficial for the player, as it reduces the possible amount of approach vectors that an enemy can use against them. The trade-off, though, will always be a reduction in the possible evasive movement vectors, so evaluating this particular scenario requires more knowledge of the enemies' behaviors.
Figure 22
Corridors like those depicted in Figure 22 are choke points which cause compression on the player -- when compressed, the player will feel extremely anxious, and move quickly to get out of this environment, especially in deathmatch type scenarios where human players will exploit these choke points.
Figure 23
Figure 24
Figure 25
Figure 26
Figure 27
Figure 28
Figure 29
Height Elements
Just as planar objects affect the metrics of space, so to do height elements. Earlier in the article, we considered how gantries could be used as an advanced type of occluder, allowing the player to gain an advantage as they have greater situational awareness.
It is also important to once again demonstrate how line of sight takes priority over virtual space in terms of metrics that determine difficulty.
Although the player will have limited evasion vectors, a gantry like the one depicted in Figure 30 will give the player strafing abilities whilst they are targeting enemies on the lower floor. The combination of these two elements combined give the player the most advantageous position in this scenario.
Figure 30
Figure 31
Figure 32
Figure 33
Figure 34
A Conclusion, of Sorts
The term "conclusion" is misleading; in terms of understanding the impacts of space on difficulty and player psychology, what is presented here is merely the tip of the iceberg. The next step in understanding virtual space is to consider that within game geometries, we have a number of attractive and repulsive forces. I have previously discussed the theoretical components of this in another article, which deals with the notion of compression and funneling, and I have hinted at its benefits throughout this article.
Understanding dynamic relationships is the next piece of the puzzle. We need to understand the dynamic forces that compel the player to move and engage with the level geometries. For now, though, this rational approach to difficulty ramping in 3D FPS games can be easily applied to your own design concepts. If spaces are designed with the player's situational awareness in mind, then we can begin to incorporate other design tools, such as Jesse Schell's interest curves, to further improve our designs.
Source: www.gamasutra.com/view/feature/176933/the_metrics_of_space_tactical_.php?
Follow Luke
Website: 330mega.wordpress.com/