Code structure

The code of VCMI is divided into several main parts: client, server, lib and AIs, each one in a separate binary file.

The big picture

VCMI contains three core project: VCMI_lib (dll / so), VCMI_client (executable) and VCMI_server (executable). Server handles all game mechanics and events. Client presents game state and events to player and collects input from him.

During the game, we have one (and only one) server and one or more (one for each player computer) clients.

Important: State of the game and its mechanics are synchronized between clients and server. All changes to the game state or mechanics must be done by server which will send appropriate notices to clients.

Game state

It's basically CGameState class object and everything that's accessible from it: map (with objects), player statuses, game options, etc.

Bonus system

One of the more important pieces of VCMI is the bonus system. It's described in a separate article.

Client

Main purposes of client

Client is responsible for:

• displaying state of game to human player
• capturing player's actions and sending requests to server
• displaying changes in state of game indicated by server

Rendering of graphics

Rendering of graphics relies heavily on SDL. Currently we do not have any wrapper for SDL internal structures and most of rendering is about blitting surfaces using SDL_BlitSurface. We have a few function that make rendering easier or make specific parts of rendering (like printing text). They are places in client/SDL_Extensions and client/SDL_Framerate (the second one contains code responsible for keeping appropriate framerate, it should work more smart than just SDL_Delay(miliseconds)). In rendering, Interface object system is quite helpful. Its base is CIntObject class that is basically a base class for our library of GUI components and other objects.

Primitive controls

VCMI provides a set of controls a window can be build from. We have already written basic counterparts of most of standard controls like buttons, labels etc. Here is a list of them:

• AdventureMapButton - standard button class for general use (its name is after its first application). Optimized for buttons having standard .DEF graphics. When it's pressed, all functions from its callback field are called.
• CHighlightableButton - basically a checkbox. Has two callbacks: one for selecting and one for deselecting. It inherits from AdventureMapButton because most of graphics handling is common/
• CHighlightableButtonsGroup - a radio button group. It consist of many CHighlightableButtons. Functions from onChange are called when selection is changed (the parameter is the ID of selected button).
• CSlider - a typical slider.
• CLabel - a label with custom font and color. It does nothing interesting.
• CPicture - any bitmap.
• CTextInput - a textbox.
• CGStatusBar - a statusbar for general use.

Adventure map interface

TBD

Town interface

TBD

Server

Main purposes of server

Server is responsible for:

• maintaining state of the game
• handling requests from all clients participating in game
• informing all clients about changes in state of the game that are visible to them

Lib

Main purposes of lib

VCMI_Lib is a library that contains code common to server and client, so we avoid it's duplication. Important: the library code is common for client and server and used by them, but the library instance (in opposition to the library as file) is not shared by them! Both client and server create their own "copies" of lib with all its class instances.

Lib contains code responsible for:

• handling most of Heroes III files (.lod, .txt setting files)
• storing information common to server and client like state of the game
• managing armies, buildings, artifacts, spells, bonuses and other game objects
• handling general game mechanics and related actions (only adventure map objects; it's an unwanted remnant of past development - all game mechanics should be handled by the server)
• networking and serialization

Artificial Intelligence (AI)

Neural network

Neural network is an unused and abandoned part of Genius AI.

Expert System

Expert system is unfinished AI module which could allow understanding of game mechanics in rule-based fashion. It is supposed to utilize bonus system which hold info about many different game mechanics and could be potentially used to build complex strategies.

Modding tools

Modding engine and tools are not yet finished nor avaliable to end user.