Functions of Game Engines

1. Functions of Game Engines U70 PMD2: Understand the functions of components of game engines Date due: Monday 22/04/13

2. From the Unit Spec – PMD2

3. PMD2 – Understand functions • 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.

4. PMD2a – Graphic rendering 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.

5. 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. 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. 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

6. PMD2b – Animation systems 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 kinematicsor forward kinematics (research these).

7. PMD2c – Other 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.

8. PMD2d – AI 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 includepathfinding 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.

9. PMD2e – Middleware 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

10. Write-Up and examples 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.

11. Write-Up and examples The following are examples of the differences between Pass, Merit and Distinction grade writing. Use them to inform your work. PMD2 – Understand methods

12. Write-Up and examples The following are examples of the differences between Pass, Merit and Distinction grade writing. Use them to inform your work. PMD2 – Understand methods