Flash Games: Make a world continuous, circular

Question

I am writing now a flash game and I run into a an issue. I have a map for the game which is defined as a 2-D array, where each element represents a component of the map. The player is always in the center of the map.

The problem is when the player reaches one end of the map. Now it is empty space. I want that the player instead of seeing the empty space, to see another end of the map and in this way, the map will loo like it goes around.

So for example if the player goes to right he will eventually start seeing the the left side of the map and the world will look continuous.

Does anyone knows how to implement this functionality?

Answer 1

You could make the array 2 times and put the first one behind the second one again and than the second one behind the first etc etc..

It's done here with 2 pictures, just use the arrays instead:

//The speed of the scroll movement.
var scrollSpeed:uint = 2;

//This adds two instances of the movie clip onto the stage.
var s1:ScrollBg = new ScrollBg();
var s2:ScrollBg = new ScrollBg();
addChild(s1); 
addChild(s2);

//This positions the second movieclip next to the first one.
s1.x = 0;
s2.x = s1.width;

//Adds an event listener to the stage.
stage.addEventListener(Event.ENTER_FRAME, moveScroll); 

//This function moves both the images to left. If the first and second 
//images goes pass the left stage boundary then it gets moved to 
//the other side of the stage. 
function moveScroll(e:Event):void{
s1.x -= scrollSpeed;  
s2.x -= scrollSpeed;  

if(s1.x < -s1.width){
s1.x = s1.width;
}else if(s2.x < -s2.width){
s2.x = s2.width;
}
}

Answer 2

You simply check if your player is about to get off the "right" or "left" edge of the map, and position him at the other edge. To draw a circular map, you can use the following technique: if you are about to draw a column of a number that exceeds the map's width, decrease that number by width and draw the column at resultant index; and if you are about to draw a column at index below zero, add width and draw the column at resultant index. If you are in troubles of making a hitcheck at continuous map's borders, you can employ the same trick to find neighbors. (The "circular array" is a pretty basic algorithmic problem, and is resolved in many ways already)

Answer 3

You have a few options here. You can do the pac-man style of just making your character pop up on the other side of the screen, but that would require you to abandon the cool bit of the character being in the middle at all times.

On to the real suggestions:

If you're not implementing your array as one solid object (i.e. making it draw individual collumns/rows at a time) then this is a no-brainer. Just have a function that returns the index of the next collumn/row, within certain bounds. Like, if your array is 40 elements wide, when it tries to draw element 41, subtract the size of the array, and make it draw element 1 instead.

If your array is one solid object (like if you drew it onto a stage object and are just manipulating that) and it's not very big, you could probably get away with drawing a total of four of them, and just having a new one cover up any whitespace that's about to appear. Like, as you approach the right edge of the first array, the second array moves to the right of it for a lawless transition.

If your array is a solid object and is very big, perhaps you could make eight buffer objects (one per edge and one per corner) that hold approximately half a screen's worth of the array. That way as you approach the right edge, you see the left edge, but then when you cross into the buffer zone, you could teleport the player to the corresponding position on the left of the array, which has the buffer for the right size. To the player, nothing has changed, but now they're on the other side of the world.