Functions of Game EnginesU70

PMD2: Understand the functions of components of game engines

Date due: Monday 22/04/13

From the Unit Spec – PMD2

GC Pass Merit Distinction

2

summarise accurately the functions of components of game engines using some subject terminology appropriately

explain components of game engines with reference to detailed illustrative examples and with generally correct use of subject terminology

comprehensively explaincomponents of game engines with elucidated examples and consistently using subject terminology correctly

• The five key subcategories of this GC are:

• Graphic rendering• Animation systems• Other systems• AI• Middleware

• Note that you must show evidence of understanding all of these categories in order to achieve the GC.

PMD2 – Understand functions

Graphic rendering is the process of an engine displaying the visual elements of a game for a player to see.• This process usually takes over 50% of a CPU’s processing power.

Because of the enormous processing requirement, culling methods are employed to reduce waste rendering. This is achieved by determining what does not need to be rendered, based on specific criteria.

Renderers often make use of several techniques in order to realistically display 3D images, including ray-tracing, fogging, shadowing and anti-aliasing.

PMD2a – Graphic rendering

Backface literally means the faces of an object which are at the back, relative to the camera’s current position. This is the most common form of culling, and is almost always applied automatically by hardware.

View frustum is the field of view at any given time. This means that objects outside the view frustum will be automatically culled; there is no point in rendering an object which is not visible to the player. This check is performed by calculating whether the geometrical position of the object will fall inside the frustum volume.

Portal culling divides a given scene into cells, with portals between them. This is most often used for indoor scenes, dividing levels into separate rooms. Essentially, objects which are not in the same cell is the camera will not be rendered, as there must be a wall between them (therefore making the object out of sight). However, when the view frustum intersects with a portal, an additional frustum will be created and calculated based on the camera’s current position. This allows objects seen through windows and doorways to be rendered.

This diagram shows how the major forms of culling work. Any faces highlighted in red will be culled due to the camera’s current position. If the camera were to move position, some of the culled faces may then need to be rendered.

Detail culling calculates whether an object would be visible based on its distance from the camera. If it is a small object which is far away, there is now need to render it. A more advanced form of this is level of detail, which scales the level of detail based on the distance, rather than on/off rendering.

Occlusion culling is the hardest form of culling to implement. It involves geometric equations to determine whether or not there is another object blocking it from view, thus making it eligible for culling.

Source

Furthers on occlusion culling

Animation systems are used to create or render models and rigs within the game engine. These can be pre-rendered, as with a walk or idle cycle, or they can be rendered real time, as with ragdoll physics.

When animating, the two primary methods are to use either inverse kinematics or forward kinematics (research these).

PMD2b – Animation systems

As well as animation systems, game engines often incorporate other system functions, or sub-engines, such as physics, sound or networking. Most modern games make use of physics and sound engines, while all online games must use some form of networking.Physics engines are often incredibly complicated, and can easily cause a great deal of problems if not properly implemented. Skate 3 has a notoriously bad physics engine.

PMD2c – Other Systems

Most games which feature NPCs will have at least some basic AI implemented. AI covers any action that an NPC is expected to take automatically, based on some form of input. Common tasks include pathfinding and obstacle avoidance, behaviours and fuzzy logic.

Fuzzy logic is probabilistic logic. This means that reasoning can be approximated or scaled, as opposed to Boolean logic, which must return either true or false.

PMD2d – AI

Middleware in the games industry usually consists of secondary engines which work alongside the primary game engine, or as a plugin to it. These can include physics, sound and rendering engines, among other things. Examples include:• Havok - physics engine• Bink - video encoding, used to play FMVs in

games• DemonWare – networking outsourcers

PMD2e – Middleware

You need to write this up as a webzine or blog articles, entitled “Game Engines And Their Functions”.

This piece of extended writing should aim to have the same written standard as that required by any other piece of theory work, but remember the specific unit requirements.

Use the unit spec as a checklist to ensure you have covered everything that you need to.

Write-Up and examples

The following are examples of the differences between Pass, Merit and Distinction grade writing. Use them to inform your work.

Write-Up and examples

Pass Merit‘In computer graphics the renderer is viewed as one of the most important parts. The renderer allows us to see the models in the game world. It basically puts all the graphics features in the game together so it can be viewed on screen. With so much to do it needs a lot of processing power. It is the part that is most often criticised when viewed by those playing the game, as graphics can play a key role in how commercially successful a game will become.’

‘Graphics rendering is viewed as one of the most important parts of a game engine. The renderer allows us to see the models in the game world properly lit, textured etc. It basically puts all the graphics features in the game together so it can be viewed on screen. With so much to do it needs a lot of processing power. About 50 per cent of the CPU’s processing power is used to pass graphical information towards the renderer. Game graphics is the part that is most often criticised by those playing a game; it can play a key role in how commercially successful a game will become.’PMD2 – Understand methods

The following are examples of the differences between Pass, Merit and Distinction grade writing. Use them to inform your work.

Write-Up and examples

Distinction‘The renderer is the most important part of every game engine, and it is usually where the building of a game engine begins. If you had no renderer you wouldn’t be able to see anything. This is because the renderer visualises the scene for the player from information passed to it by the game engine. The CPU spends over 50 per cent of its processing time on the rendering process. If the game developers get the rendering wrong it can cause the whole game and company to look like a joke in the game world, so they have to get it right. The renderer’s job is to give the game the excellent graphics that people love to see in games. If you have the best renderer available then you have the potential to make the best game from a graphics point of view. OpenGL and DirectX are well known for their rendering capabilities and are widely used in the professional market because of their reliability.’

PMD2 – Understand methods