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开发者分享3类动态难度调节机制及其具体应用

发布时间:2019-11-06 08:59:35 Tags:,

开发者分享3类动态难度调节机制及其具体应用

原作者:Caleb Compton 译者:Vivian Xue

在上周的文章中,我探讨了一些游戏中最有趣也最常见的隐藏机制。然而,有一类隐藏机制相比之下更加多样化且普遍——调整游戏难度和平衡的机制。这些机制被总称为动态难度调节(dynamic difficulty adjustment,下文简称DDA)。

DDA是电子游戏根据玩家水平调整游戏难度的过程。若玩家表现优秀,游戏将加大难度和挑战。相反,若玩家打得很吃力,游戏可能会降低难度帮玩家度过难关。

DDA分为短期和长期两种。短期DDA与游戏的随机数生成器挂钩,目的是为了防止玩家遇到极端情况,一直幸运或一直倒霉。这些随机系统在某些时刻对游戏进行平衡,一般不会对游戏进程造成长远影响。

而长期DDA是根据玩家的水平调整游戏的整体难度。由于每位玩家的技能水平不同,统一的难度等级或选项无法覆盖所有玩家的需求。长期DDA的目标是使游戏对每位玩家来说既具有挑战性,又可克服。

最后,还有一种“永远开启”的难度调节系统。这些系统总是在游戏中呈活跃状态,在不引起玩家察觉的情况下提高或降低游戏难度。当玩家期待游戏有所改变,当玩家的内隐行为发生变化,这些系统将派上用场。

1. 橡皮筋效应

一种最常见,且最受批评的DDA运用被称为“橡皮筋效应”。这种应用常见于赛车游戏中(尤其是《马里奥赛车》系列),之所以这样命名是因为玩家和电脑对手仿佛被一根橡皮筋连了起来。

这种DDA的工作方式是,玩家领先时,电脑对手加速,玩家落后时,电脑对手减速。玩家领先或落后得越多,电脑对手的反应就越活跃。这种DDA目的是使比赛更具“竞争性”,防止玩家在领先或落后太多。然而它极容易被玩家察觉,并且由于电脑对手不受该系统限制,玩家会感觉不公平。

虽然“橡皮筋效应”是赛车游戏的突出特点,许多其它类型游戏中也存在相似的机制。例如在体育游戏中,AI对手总是在玩家领先时突然变强,或者是在RPG中,敌人随着玩家升级而变强。

这些机制不一定总是糟糕的,但它们经常被过度使用。虽然紧张刺激的角逐令人向往,有时把对手远远甩在后头(或者让玩家来控制电脑对手的强弱)同样能带来满足感。在许多情况下,橡皮筋机制与其它形式的DDA并无不同,除了一点,它很容易被察觉。成功的DDA应该是无形的——玩家永远感受不到它。

Super Mario Run(from mit)

Super Mario Run(from mit)

2. 短期DDA

某些DDA考虑的不是控制游戏的整体难度,而是确保玩家不会因游戏的随机数生成器而一直幸运或倒霉。几乎所有电子游戏中都存在某种随机数生成器,当事情不如你所愿时,你总是感觉很失落(任何连续错过90%命中率攻击的宝可梦玩家都可以证明这一点。)

另一个存在随机数生成器的游戏是《幽浮:未知敌人》(XCOM: Enemy Unknown),当你在打普通或简单模式时。在这款策略游戏中,玩家能够看到每次攻击的命中率,然而这些数字并不可靠——在简单模式中,实际命中率是显示命中率的120%。

此外,游戏会根据之前的情况调整这些百分比。如果玩家已经失去了队友,或者连续几次错失目标,命中率会被调高。同样的,如果外星敌人连续多次攻击成功,它们的命中率会被降低。

另外一个例子是《马里奥赛车》的随机道具系统。玩家越接近第一名,他们获得的道具就越差。当玩家排在首位时只能获得金币和绿龟壳(游戏中最弱的增强道具),排在第12名时能获得极强的道具,比如蓝龟壳(能够追踪并撞倒第一名,基本上无人能挡)和炮弹比尔,这将使玩家在短时间内全面提速,处于无敌和自动驾驶状态。

这是一种短期DDA,它基于你在比赛过程某一时刻的名次。当你使用炮弹比尔倒一跃升到第一名,你会立刻发现自己获得的道具弱的多。这种道具分配系统会加强“橡皮筋效应”。

3. 长期DDA

一种普遍的长期DDA形式是让整个游戏世界随着玩家升级而升级。《辐射》、《上古卷轴》等游戏都运用了该系统,它将玩家的等级作为能力的代表,据此调整敌人的强弱。这将防止玩家达到某个级别后轻松秒杀敌人而导致游戏变得过分简单。

另外一种长期DDA通过跟踪玩家的行为(比如死亡频率和升级速度)来逐渐调整难度。例如,当玩家死亡频率过高时,游戏会通过一些微调变得更简单。这将帮助玩家通过游戏最难的部分,防止他们进入死循环。

DDA能够调节的因素有很多,包括敌人的速度、血量、数量和灵敏性,玩家的血量或攻击伤害,还有一些环境因素例如道具数量或时间限制。通过逐步微调这些因素,比如在玩家每次死亡后把难度调整到一个理想的状态,使玩家无法察觉。

这样做的一个例子是《寂静岭:失落的记忆》。玩家在噩梦中被敌人追着跑,游戏会在玩家每次死亡后慢慢调整难度,从而使玩家得以前进。他们采用的做法是移除AI敌人的一个“感官”(如嗅觉、听觉和视觉),使敌人更难发现和追踪玩家。当玩家死亡次数达到一定数量,游戏开始减少敌人的数量。

4. “永远开启”

最后一类DDA与前面几种不太一样,因为从技术的角度来看它们不属于难度调节。然而,它们与DDA存在关联,因为它们以一种玩家(但愿)无法察觉的方式影响游戏难度。唯一的区别在于它们永远处于活跃状态——它们不会基于玩家表现而变化。

一个很好的例子是《鬼泣》(Devil May Cry)系列。尽管同时面对一大群敌人感觉很刺激,但无法抵挡背后的攻击,或者同时面临太多威胁而无力应对也会令人痛苦。这也是为什么在这款游戏中(和许多其它游戏中),镜头以外的敌人会放慢攻击速度甚至完全停止攻击,从而让玩家专注于他们所能看到的威胁。

《半条命》采用了相似做法。由于同时应对成群的敌人是如此困难,游戏对敌人进行设定,最多两名敌人同时向玩家发动攻击,剩下的则在四周奔跑对玩家进行包抄。

另外一种“永远开启”的难度调节表现在游戏的碰撞系统上。例如,在许多平台游戏中,游戏允许玩家在脱离平台边缘的一瞬间跳跃。这可以避免玩家因太慢按下跳跃键而挂掉的情况。

相似地,物体的击中判定面积并不一定像它们呈现的那样。尽管有时这可能令人失望或产生错误,但你也可以将它转化为有利的事物。举个例子,我们可以把一些积极的物品(如增强道具和收集物)的击中判定面积做大一些,使它们更容易被收集。

相似地,我们也可以把地雷或导弹这类物体的判定面积缩小一些。以免玩家觉得自己躲掉了攻击,结果还是被打中了。

本文由游戏邦编译,转载请注明来源,或咨询微信zhengjintiao
In last week’s article I examined some of the most interesting and common hidden mechanics in games. However, there is one category of hidden mechanics that is more varied and pervasive than any other – mechanics that adjust the game’s difficulty and balance. These mechanics are collectively known as dynamic difficulty adjustment.

Dynamic difficulty adjustment (DDA) is a process in which video games will adjust the difficulty of the game over time based on the player’s performance. If the player is doing well the game will become more difficult to add challenge. On the other hand, if the player is struggling the game might reduce the difficulty to keep them from getting stuck.

Dynamic difficulty adjustment can be both short term and long term. Short term DDA usually has to do with the game’s random number generator, and is designed to prevent the player from having long strings of extreme luck, whether good or bad. These systems are more about balancing in the moment, and don’t generally have long term effects on the game going forward.

Long term adjustments, on the other hand, are designed to adjust the difficulty of the entire game to a level that the player can handle. Because every player has a different skill level having one single level of difficulty, or even a handful of options, is not going to be able to cover all players. Long term adjustments are designed to make the game challenging, but surmountable, for each individual’s abilities.

Finally, there are “Always On” difficulty techniques. These techniques are always active in the game, and are designed to make the game more or less difficult without the player ever noticing. These systems come into play when the player has certain expectations about how the game should behave, when the actual internal behavior is different.

1. The Rubber Band Effect

A common, and much criticized, usage of DDA is what is known as “rubber banding”. This technique, which is commonly associated with racing games (and especially the Mario Kart series), is so named because it creates the feeling that the player and their computer opponents are connected with a rubber band.

The way this technique works, when the player is ahead the opponents speed up, and when the player is behind they slow down. The further ahead or behind the player is, the more the computer opponents react. This technique is designed to make the race more “competitive”, and prevent the player from getting too far ahead or behind at any point. However, this technique can be extremely obvious to the player, and it can feel unfair that the computer doesn’t have to follow the same rules as the player.

While true rubber banding is isolated to racing games, many other games can incorporate mechanics that feel very similar to rubber banding. An example of this would be a sports game where the AI team gets better the further ahead the player is, or an RPG where enemies level up to keep up with the player.

These techniques are not necessarily inherently bad, but they are often used too aggressively. While it can be tempting to make every race / game close and suspenseful, it can also be equally satisfying to leave your computer opponents in the dust (or give your player the power to control how tough the computer should be). In many ways, rubber band mechanics are no different from other forms of DDA, except that they are easily noticed by the player. For DDA to be most successful, it should be invisible – the player should never feel it happening.

2. Short-term Thinking

Some forms of dynamic difficulty adjustment are less about controlling the overall difficulty of the game, and more about making sure that the player does not experience long strings of luck (good or bad) from the game’s random number generators (RNG). Pretty much every video game has some RNG elements, and it can be very frustrating when things just don’t go your way (as anybody who has lost in Pokemon because they keep missing a 90% accurate move can attest).

An example of this can be found in the XCOM: Enemy Unknown, if you are playing on the normal or easy difficulties. In this strategy game series players are shown a percentage for each attack, which represents their likelihood to successfully hit the opponent. However, these percentages are not reliable – on Easy difficulty the actual percentages are 120% of what is shown.

In addition, the game adjusts these percentages over time based on previous events. If the player has lost teammates, or has missed several times in a row, their odds of hitting will go up. Similarly, if the alien opponents have hit several times in a row their chances will be reduced.

Another example can be found in Mario Kart, in the way the game distributes items. The closer the player is to first place the worse items they get. While first place may only get coins and green shells (the weakest boosts and projectiles in the game), 12th place will get extremely powerful items such as blue shells (which home in on first place and are practically unavoidable) and bullet bills, which give them an extreme boost of speed, invulnerability, and autopilot for a short time.

This type of item distribution is short term because it is only based on your position in the race at the moment. If a bullet bill helps you go from last place to first, you will immediately notice that the items you are receiving are far weaker. This item distribution can also increase the sense of rubber-banding, as described earlier.

3. Long-term results

One common form of long-term DDA is to have the world level up as the player does. This technique, which can be found in games such as the Fallout and Elder Scrolls series, uses the player’s level as a representation of how powerful they are, and adjusts the strength of enemies accordingly. This prevents the game from getting too easy once the player has reached a certain level and is able to easily defeat all the enemies.

Another long-term technique that is often used is to track the player’s behavior, such as how often they die and how quickly they are making progress through the game, to adjust the difficulty over time. If the player is dying too frequently, for example, the game can make some slight adjustments to make the game easier. This can help the player get past difficult sections of the game, and can prevent them from getting stuck indefinitely.

There are a countless number of factors that can be adjusted by DDA. These include things such as the speed, health, amount and intelligence of enemies, the player’s health or damage output, and environmental factors such as increasing the amount of items or adjusting a time limit. By slightly adjusting these factors over time, such as each time the player dies, the game can adjust its difficulty to the desired level in a way that the player will never notice.

A great example of this can be found in Silent Hill: Shattered Memories. During nightmare scenes when the player is being chased by enemies the game slowly adjusts the difficulty each time the player dies until they are able to move forward. The way this is done is by removing a “sense” (such as smell, hearing, and sight) from the AI enemy, which makes it harder for them to detect and locate the player. If the player dies enough times it also begins to reduce the number of enemies.

4. “Always On”

This final category is a bit different than the previous ones, because it is technically not a form of difficulty adjustment. However, these examples are related to DDA because they affect the difficulty of the game in a way that players will (hopefully) never notice. The only difference is that these hidden effects are always active – they don’t change based on player performance.

A great example of this can be found in the Devil May Cry series. While it can feel amazing to take on a huge group of enemies at the same time it can also suck to be blindsided by attacks from behind, or have so many threats that you cannot respond to all of them. This is why in this game (and many others) enemies that are not currently on-screen will often slow down or even stop attacking entirely, to allow players to focus on what they can see.

A similar technique can be found in Half-Life. Because it can be so difficult to deal with hordes of enemies at the same time the enemies were actually designed so that no more than 2 would attack the player at the same time. The rest of the enemies would instead run around the player to “flank” them.

Another way to create these “Always On” adjustments is to tweak the way that collisions work in your game. In many platforming games, for example, there is a short period of time where players are still allowed to jump after walking off a platform. This can prevent situations where players fall to their deaths because they waited slightly too long to press the jump button.

Similarly, the collision boxes around objects in games are not always exactly what they would appear. While this can occasionally be frustrating or a mistake, it can also be used to your advantage. An example of this would be making the hitbox around positive items, such as power-ups and collectibles, slightly larger than expected to make them a little easier to collect.

Similarly, you could make the collision around things such as landmines or projectiles slightly smaller than they appear. This can prevent situations where players believe that they avoided the obstacle, only to be hit by it anyways.

Until Next Time! (source:Gamasutra

 


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