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 projects: 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.

Configuration

Most of VCMI configuration files uses Json format and located in "config" directory

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.

Video player

Located in client/VideoHandler.cpp/.h, have several platform-specific versions:

• For 32-bit Windows - using original 32-bit libraries (binkw32.dll, smackw32.dll)
• For *nix systems - using ffmpeg libraries.
• Empty player for 64-bit Windows

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

Serialization

The serialization framework can serialize basic types, several standard containers among smart pointers and custom objects. Its design is based on the boost serialization libraries. In addition to the basic functionality it provides light-weight transfer of CGObjectInstance objects by sending only the index/id.

Different major version of VCMI likely change the format of the save game. Every save game needs a version identifier, that loading can work properly. Backward compatibility isn't supported for now. The version identifier is a constant named version in Connection.h and should be updated every major VCMI version and eventually development versions. Do not change this constant if it's not required as it leads to complete re-compilations. Why should the version be updated? If VCMI cannot detect "invalid" save games the program behaviour is random and undefined. It mostly results in a crash. The reason can be anything from null pointer exceptions, index out of bounds exceptions(ok, they aren't available in c++, but you know what I mean:) or invalid objects loading(too much elements in a vector, etc...) This should be avoided at least for public VCMI releases.

Artificial Intelligence (AI)

GeniusAI

Genius AI is first and obsolete battle AI. It was removed from trunk, yet it contains some potentially useful utilities like neural network.

StupidAI

Stupid AI is recent and used battle AI.

Adventure AI

VCAI module is currently developed agent-based system driven by goals and heroes.

Neural network

Neural network is an unused and abandoned part of GeniusAI.

Fuzzy logic

VCMI includes FuzzyLite library to make use of fuzzy rule-based algorithms. They are useful to handle uncertanity and resemble human behaviour who takes decisions based on rough observations. FuzzyLite is linked as separate static library in AI/FuzzyLite.lib file.

Modding tools

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

Mod system proposal