Theme Park Builder 3D The Game

Technical Design Document Graphics

General Water Details

Water is a multi-component entity composed of a surface, refraction and layers of alphas and visual effects.

Role

Entity

Dependencies

Agents, Construction, (Game Agent).

Synopsis

It should be possible to have several people working on different sections. This project is strong on C++ classes using some high level patterns which is necessary for several reasons. Organization is the first big reason, it makes the project manageble as this thing will become enormous at some point. Next is the ability to build simple modules that all work together ans inherit basic functionality like saving data, all objects have that ability. Then there us the need for multi threading. Because the AI is seperate from the main code, it can thread off to do path finding on a second core while the game plays on. RCT had to write elaborate timing sequences to do the same. The other is the ease of adding in the networking code. This thing will have a central hub that passes all communications from module to module.

Description

Look up the object pattern "Chain of Events" and "Delegates" for what this pattern's behavior. User input generates click, keystroke and movement events. This event pattern delivers these event to their intended target. Events are not connected directly to ride parts, graphics or even the agents that drive the engine. Instead events are linked to subscribers that handle the message and direct it to the appropriate delegate for the task. The delegates or tasks assigned are assigned tp event stream for a particular operation or movement. The event agent creates these delegates from templates and then assignes them to the event when the user selects options from the menus or clicks objects. The templates are thin classes that are easily mutalble to handle differnt tasks and behaviors. Once an event is dispatched to a delegate it can consume it or pass it to the next in the chain. One or more delegates may respond to a single event depending on use. The first one to get the event can respond and end the event or pass it on to the next delegate. If the delegate consumed it buy performing an action it may return null breaking the chain or true to pass it along. In the case of the Undo/Redo system, the event is obsereved, data collected and passed to the next in the chain.

Event Recap

To garrantee an action gets attention it must be the first or second to get it.

First to use the event may be the only one so pay attention to events in the same chain when setting one up.

A delegate must be considerate to pass it on if nothing ocurred in that delegate's domain.

This event system is also used in the game Highrise Developer a Tower building simulator. The beauty of this is that the delegates can be swapped as user operations are changed. Say you click add feature like Add Street Lamps. A delegate is built from a template to an agent that builds park elements. The agent is also sent parameters as to which street light was selected. Then when the used moves the pointer, a streetlight appears there as a ghost image for placing and allignment. When the used clicks the left button the object will be placed. If the user clicks the right button an option menu may appear or other operaion. Some of this logic will already be working in the initial code so you will get to see it first hand.

Advantages

Little or no switch logic is needed

Highly maintainable since delegates are small specialized classes.

High degree of seperation between UI and programming logic.

Team work allows for one coder on the UI and another on the logic.

Disadvantages

Steaper learning curve, transparency shields event initiators from logic.

The number of templates specialized may become extensive in later development.

Event Base Class Implementation (EventBase)

Properties: Protected

None

Methods: Public Virtual

Preliminary list which only covers basics

bool OnResize (Vector2i viewSize) return false; bool OnMouseDown (int Button, Vector2i Scene, Vector2i Camera) return false; bool OnMouseUp (int Button, Vector2i Scene, Vector2i Camera) return false; bool OnKeyDown (int Key) return false; bool OnKeyUp (int Key) return false; bool OnMouseMove (Vector2i Scene, Vector2i Camera) return false; bool OnMouseWheel (int Delta) return false; bool OnClose () return false; bool OnToolHit (const std::string& Name) return false; bool OnOpen (const char* pPath) return false; bool OnSave (const char* pPath) return false;

Notes

Events are the messenger for front end modules to interact with agents and objects. Delegates provide the link from the event trigger to the destination handler. Delegates are swappable eliminating switch logic which makes the code more responsive. At first this metodology is perplexing due to the transparency of the sender to handler relation. Once we are accustomed to the event logic, it becomes easier to build up features and assets. The event handler allows for real time acction response and multi threading. IE: If you change the language settings in the preferences the game changes right there.