Data organization in the assignment
Marek Trtík
PA199
2
Typical game architecture
Math
Graphics
Physics
Audio
Network
AI
Animation
Engine libraries
Scripting
…
Game data
Game
mechanics
Game libraries
Quests/story
system
…
Our
Focus
3
 General enough for games:
 Game objects are often composed in an acyclic hierarchies, e.g.,:
 Car – the wheels and doors are attached to the body.
 Animation skeleton – bones form a tree.
 Items (like weapons) are attached to an agent/player.
 Simple to implement and easy to traverse (tree DFS, BFS):
class GameNode {
GameNodeWeakPtr parent;
std::list<GameNodePtr> children;
…
Game data: Tree structure
4
class GameNodeHierarchy { // The only owner of all nodes
GameNodePtr root;
public:
static GameNodeHierarchy& instance(); // Singleton
template<typename NodeType, class... ParameterTypes>
std::shared_ptr<NodeType> push_back_child(
GameNodePtr parent,
ParameterTypes... args);
…
Game data: Tree structure
5
 A component is a class instance of some Engine/Game library.
 Holds specific data.
 May also provide a functionality – code.
 Allows for a data-driven approach:
 Attaching components to a GameNode => Specification of node’s
purpose in the game.
 Intuitive and easy to use.
 Also easy to implement:
Game data: Component based
6
class Component {
bool active;
GameNode* node; // The node this component is attached to.
public:
virtual ~Component() {} // IMPORTANT: Allows for an inheritance!
…
 We need to extend GameNode to store attached components:
Component system
7
class GameNode {
…
std::list<ComponentPtr> components;
public:
template<typename ComponentType>
std::shared_ptr<ComponentType> find_component() const;
void push_back_component(ComponentPtr component);
…
 An important component for a game is a frame of reference:
Component system
8
class Frame : public Component { // Frame of reference
FramePtr parent; // A frame in which this one is defined.
// We do not need to know about children.
Vec3 origin;
Quat orientation;
Vec3 scale; // Optional; for uniform scaling use just: float scale;
mutable Mat44* to_world; // Cached; compute on demand.
mutable Mat44* from_world; // Cached; compute on demand.
…
Frame of reference
9
 We can define a script component:
class GameScript : public Component {
public:
virtual void update() {} // To be called by ScriptingEngine
};
 A simple scripting engine can then be defined as follows:
Scripting in C++
10
class ScriptingEngine {
std::list<GameScriptPtr> scripts;
public:
static ScriptingEngine& instance(); // Singleton
void update(); // Call ‘update’ on each script.
template<typename ScriptType, class... ParameterTypes>
std::shared_ptr<ScriptType> create_script(ParameterTypes... args) {
auto script = std::make_shared<ScriptType>(args...);
scripts.push_back(script); // Keep track of all created scripts.
return script;
}
…
Scripting in C++
11
Example: Data hierarchy of our game
Ball
SphereCollider
SphereController
…
Frame
Paddles
PaddlesController
Frame
Paddle1
…
Frame
Wall
WallController
Frame
Brick1
Frame
…
Ground
Frame
…
… …
Root
12
 A sketch of an implementation of the discussed topic is in IS:
game_data_hierarchy.ZIP
Reference