Display/update loop

• As much as possible, you want to separate your actual drawing (display) from your game logic (update).

• You want to update at a constant frame rate. If you don’t, as you add more objects to your scene, the game will slow down.

A simple display/update loop:

while (TRUE)

{

while (elapsed < frame_time);

DisplayScene();

UpdateScene();

}

• Another option is to keep the update rate constant, but display as quickly as possible. This will also handle crappy machines with slow displays.

A fancier display/update loop:

while (TRUE)

{

while (elapsed < frame_time)

{

DisplayScene();

}

UpdateScene(elapsed);

}

Actors

• No matter what your game involves, see if you can use actors to play the parts
• Enumerated types! Make an enumerated type showing all your actors

typedef enum

{

ACT_RIGHTWING,

ACT_CENTER,

…

ACT_GOALIE,

ACT_WATERBOY,

ACT_CHEERLEADER1,

}

Actor* gameActors[MAX_ACTORS];

• Then you can access each individual member of the gameActors array be just saying: gameActors[ACT_WATERBOY]
• And now, of course, you can loop through your entire actors array to perform operations (like drawing, updating animations, etc.) on them.

Tasks

• Actors can perform tasks, that often cause specific animations to be played. Make tasks an enumerated type, just like your actors.

if (InGoal(ball, goal))

{

SetTask(ACT_GOALIE, TASK_COLLAPSE);

SetTask(GetGoalScorer(), TASK_CELEBRATE);

for (i=0; i<NUM_CHEERLEADERS; i++)

{

SetTask(ACT_CHEERLEADER1+i, TASK_SHAKEIT);

}

}

More on displays

void DisplayActors()

{

for (actorNum=0; actorNum<NUM_ACTORS; i++)

{

Actor* actor = gameActors[actorNum];

DisplayFrame(actorNum,

gameAnimations[actor->currTask][actor->currFrame];

}

}

State Machines

• Make a state machine indicating which game state you’re currently in (STATE_PREGAME, STATE_INGAME, STATE_AFTERGOAL, etc…), and make decisions based on game events, user input, and your current state.
• You can use state machines for buttloads of other stuff too. As an example, for opponent AI, you can have actors be in either a (STATE_TRACK, STATE_RETREAT, STATE_PASS, STATE_SHOOT, STATE_RUN_FOR_PASS) state, and have it change depending on game conditions at the time.