Object-Oriented Design: What You Need to Know -Part 2

BTEC Extended Diploma in Computer Games Design

Unit 71: Object-Oriented Design for Computer Games

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Object-Oriented Design: What You Need to Know

Advantages of Using the Following Objects:

> Sprites; A sprite is mainly used within 2D game making, however it can be found within 3D also. It is used to represent an object, it is more common in 2D games, as it is a flat image that can be animated through changing the image frame to progress the movement. As you can see below, the sprite is a basketball and it changes state to form the frames to make it look like it is bouncing through animation.

> Characters; Characters often shape a game, either through their story or their actions. There are some genres of game that require no characters, but genres such as First/Third person and RPG etc, depend on a good strong character to shape the story of the game.

> Weapons; Weaponry within a game depends on genre, again, some games can get by without any weapons. However games like Shoot ‘em ups and Strategy RPG games rely on weapons. As you can see below, it’s not just guns that are considered as weapons. Tools, Swords, Knifes, Daggers… The list is endless. Game makers are getting more and more creative with weapon choice.

> Rooms; Rooms within a game often make up the playable area, that generally consists of multiple rooms. Rooms often have different collectibles within them, this could be different weapons or power-ups, sometimes even clothes or medical supplies. For example, below is a in game screenshot of Call of Duty: Black Ops II Zombie Map- Town. The player is in one of five rooms across the map. There is no significant power-ups or weapons within this bit of the map, however it is a wide open space often used to create some space between you and the zombies. 

> Scenery; Scenery within games is important to set the story, as well as the feel within the game. Below is a scene from Skyrim, a medieval adventure game set in a fictional country, Skyrim. The eerie mountains and old villages set the scene and feel to the game perfectly. The scenery is a vital aspect to any game in order for the genre, story and artistic elements to connect and flow in exceptional way.

> Instances; Instances within 3D game making and 2D game making vary significantly. Within 3D game engines, Unreal in particular, instances are found within the objects assets, such as their materials. Where as a 2D software such as Game Maker, use instances to change the course of events. For example, if the player was to collide with a locked door and there was an instance in place the engine could check to see if the instance count of an object, such as a key, had been collected, if so the door would unlock. This is how a lot of things work within Game Maker.

> Rewards; Rewards, such as power-ups, extra health or bonuses,  often boost the game play. There may come a time where the player is short of lives or low on health, finding an extra life or additional health, the chances of encouraging the player to play on will rise. Each reward would be their own OOD and each would function in their own ways, some would be similar in what assets the have and use, but solely individual also.

How are the Following Objects Defined within Specific Game Objects?

> Colour; The colour of an object is defined not only by sight, but through the material it is connected with. In some cases, it could have multiple colours. However the base colour or the subsurface colour is how the object would be identified.

> Size; The size of an object can most obviously be recognized by the size of said object. Also through the Details panel, within the transform section, there is Location, Rotation and Scale. Not only can you identify an objects size through here, but you can also alter it.

> Speed & Movement; Both speed and movement can be visually identified, however it can be identified through the blueprints that make the movement possible. Animating through unreal can be tricky, but once it has been digested and condensed into simpler terms it seems pretty easy to understand. The speed of the animation can be set through a blueprint also.

> Sounds; Importing sounds into Unreal is the easiest way to an atmosphere and emphasis into the game. Once the sounds have been imported, creating the blueprint gets a bit more trickier. Depending on the depth and detail of the sounds, the blueprint could be very large and complex like below, or it could be much simpler.

> Health & Lives; Health is a huge factor in most games, lives too. The importance of health in a game such as Legend of Zelda or Mario is pretty big, without lives or health, the game is over and you have to start again from the last save. Implementing a health system into unreal is done by using a blueprint widget. It gets more complex when it comes to adding and taking away the health, as well as drawing the health bar.

Actions and Events of Some Objects:

> Characters; Characters are the main part of each game, using Link from the Legend of Zelda series as an example. You can see that the state of Link is that he is mainly wearing green and he is carrying weaponry. The behaviours of Link are mostly swordplay and general movement. The actions and events of Link are the main aim of the game, Rescue Princess Zelda. All of Links actions revolve around this one task.

> Weapons; Like previously mentioned, game developers are getting more creative with the weapons they're designing. Below is the Raygun Mark II from the DLC pack that gave us Buried on Call of Duty: Black Ops II Zombies. It is a zombie exclusive gun and is very powerful. The actions of weapons are most obviously, the damage in the health of other characters or enemies. The main event for the Raygun Mark II would be when the gun is presented to the player when they open the mystery box and gain the ability to play with this weapon. Generally speaking, the main events for any weapon would be the damage caused and executing different levels of damage.

> Rewards; Rewards within games are a huge boost the the playing experience, whether it be a new weapon, a boost in health or unlocking a new area, rewards keep the player playing. The most recognized game for power ups would be the Mario series. From mushrooms changing the size of the player to giant chain chomping metal balls, the power ups in Mario are infamous in themselves. Rewards can change the course of the game, either good or bad. In terms of implementing them within Unreal blueprints, a collision event would be put into place, the rest would vary on the type of reward gained. As well as the blueprints varying, the events and actions would also depend on the type of reward earned.

> Sounds; The events of a sound blueprint would include all of the different inputs and outputs needed to execute the sound. The sounds could be triggered by the players actions, this could be by walking into a trigger box or a specific area. Another action that could cause a sound to be played could be during a battle, the clink of swords or echoing gunfire.

> Lives; In some action rpg mmo games, it isnt just health and lives that the player has to keep track of. You can see below two bars, the top bar in the green resembles the players life, the blue bar at the bottom represents how much mana a player has left. This particular health bar is from the game League of Legends. Mana is used when preforming special moves, however some characters have unlimited mana so don't have to replenish it by drinking a potion. Potions are a common thing in games with health bars, they help to restore health when the player drinks them. Looking at the potions, the action would be the player consuming the health potion and the event would be gaining  full, or partly restored health.

Implications of the Following Inheritance:

> Parent - Child; Parent - Child Behaviours can cause problems within blueprints, sometimes the child object doesn't maintain the variables and values that are inherited from the parent object. This sometimes interferes with the values that the object is trying to put into place for themselves.

> Inherited Behaviours; Much like within the real world, a child, or child object, will reference what their parent does and often mimic and copy what they see. This is the same within Unreal. Like previously stated, the child object will create their own values and assets, but will still have a section of values and assets inherited from the parental object. The values will all work the same.

> Overriding Events; Objects within unreal can override each other, sometimes this can cause errors, like seen below. Other times, you can only override objects that have output functions. This limits the functionalable blueprints.