The class project has three major components: the input client, the Stratagus game engine and the Battle of Survival data files, and the Visual Analytics application and its data files. Stratagus and Visual Analytics are already provided for you, but you may modify them as you see fit. You will need to implement your own input client, or clients, in order to develop your interaction technique.
Your input client, or clients, is where you will generate input events and send them over the network to either Stratagus or Visual Analytics. Each of these applications support mouse and keyboard input only, so you will need to translate all actions in your input client to a mouse or keyboard event. If for some reason your technique cannot be mapped to keyboard or mouse input, you will be responsible for changing the application in such a way that your technique is supported.
For both applications, actions must be translated to SDL events. To shield you from most of the gory details, we have developed an InputClient class that you may use in your input clients. The InputClient class has the following interface:
class InputClient
{
public:
InputClient(char* hostname, int port);
~InputClient();
void BuildMouseButtonDown(int button);
void BuildMouseButtonUp(int button);
void BuildMouseButtonDown(int button, int x, int y);
void BuildMouseButtonUp(int button, int x, int y);
void BuildMouseMotion(int x, int y);
void BuildKeyDown(SDLKey key);
void BuildKeyUp(SDLKey key);
void SendEvents();
};
The InputClient constructor takes hostname and a port. The hostname should almost always be gigapixel.cs.vt.edu and the port should be in the range 15000-15010.
BuildMouseButtonDown and BuildMouseButtonUp take a button code and optionally an X and Y location where the mouse was pressed or released. The X and Y parameters are just for convenience. The same effect could be achieved by composing BuildMouseMotion with BuildMouseButtonDown and BuildMouseButtonUp. The resulting event is placed on a queue.
BuildMouseMotion takes an X and Y location that the mouse was moved to. The resulting event is placed on a queue.
BuildKeyDown and BuildKeyUp take the key code of the button that was pressed. The resulting event is placed on a queue.
SendEvents transmits events to the server in the order that they were added to the queue.
The code repository has a few examples of using this class to implement simple variations on the mouse and keyboard interaction technique.
We managed to modify the stratagus game engine to not only poll the SDL event queue, but to also poll the network for SDL events. This was the simplest and most elegant way to create an interaction framework for the game in the amount of time we had. If it is impossible for you to translate your interaction technique into mouse and keyboard events, then you will need to make modifications to the game engine. Depending on the modifications, this may or may not be extremely difficult. For example, a multi-cursor modification would fall under the extremely difficult category. If your input client needs to have access to some information about the state of the game, you will need to find the part of the engine that deals with that state, serialize it, and send it over the network. This is not terribly difficult and Mike should be able to help you. If you need to send information in addition to the SDL event over the network, this is easy, and again, Mike can help you.
The following table details which keyboard buttons are bound to which game commands by default. Most of these bindings can be modified in the Battle of Survival script files if necessary.
| Cancel Commands | |
| Cancel | SDLK_ESCAPE |
| Cancel Upgrade | SDLK_ESCAPE |
| Cancel Build | SDLK_ESCAPE |
| Cancel Train Unit | SDLK_ESCAPE |
| Unit Commands | |
| Unload | SDLK_u |
| Move | SDLK_m |
| Stop | SDLK_s |
| Attack | SDLK_a |
| Patrol | SDLK_p |
| Stand Ground | SDLK_t |
| Resource Commands | |
| Repair | SDLK_r |
| Harvest | SDLK_h |
| Return Goods | SDLK_g |
| Build Commands | |
| Build | SDLK_b |
| Vault | SDLK_a |
| Generator | SDLK_g |
| Training Camp | SDLK_c |
| Development Yard | SDLK_d |
| Research Facility | SDLK_r |
| Hospital | SDLK_h |
| Vehicle Factory | SDLK_v |
| Missile Silo | SDLK_m |
| Vault Units | |
| Engineer | SDLK_e |
| Training Camp Units | |
| Assault | SDLK_a |
| Grenadier | SDLK_g |
| Bazoo | SDLK_b |
| Hospital Units | |
| Medic | SDLK_m |
| Vehicle Factory Units | |
| APC | SDLK_a |
| Harvestor | SDLK_h |
| Research Facility Commands | |
| Explosives Level 1 | SDLK_e |
| Explosives Level 2 | SDLK_e |
| Drill Level 1 | SDLK_d |
| Drill Level 2 | SDLK_d |
| Void | SDLK_v |
| Building Commands | |
| Harvest/Mine | SDLK_h |
| Move | SDLK_n |
| Stop | SDLK_c |
| Attack | SDLK_i |
| Special Unit Commands | |
| Heal (medic only) | SDLK_b |
| Nuke (missile silo only) | SDLK_n |
| Group Commands (where {#} is a number between 0 and 9) | |
| Make Group | SDLK_RCTRL (or SDLK_LCTRL) + SDLK_{#} |
| Add to Group | SDLK_RSHIFT (or SDLK_LSHIFT) + SDLK_{#} |
| Add to Other Group | SDLK_RALT (or SDLK_LALT) + SDLK_{#} |
| Selection Commands (where {#} is a number between 0 and 9) | |
| Select Group | SDLK_{#} |
| Select None | SDLK_CARET |
| Other | |
| Pause | SDLK_RCTRL (or SDLK_LCTRL) + SDLK_p or SDLK_PAUSE |
| Help Menu | SDLK_RALT (or SDLK_LALT) + SDLK_h |
| Quit Game | SDLK_RALT (or SDLK_LALT) + SDLK_x |
| Quit to Menu | SDLK_RALT (or SDLK_LALT) + SDLK_q |
The visual analytics application also uses SDL mouse and keyboard events. This was not strictly necessary, but we chose to implement it this way to make interaction techniques as portable as possible between the two applications.