Defined in Module impact.background-map, inherits from ig.Map


// Create BackgroundMap
var data = [
var bg = new ig.BackgroundMap( 16, data, 'media/tileset.png' );

// Move
bg.setScreenPos( 25, 10 );

// Draw


An ig.BackgroundMap draws tiles from a Tileset, as indicated by its 2D data Array.

The size of the tileset image must a multiple of the tilesize, otherwise Impact will get confused with the tile numbering. E.g. with a tilesize of 32 the width and height of your tileset image should be one of: 32, 64, 96, 128…

You can either create a BackgroundMap by hand, or use the ig.Game class' .loadLevel() method, which takes the save data from Weltmeister and creates BackgroundMaps according to it.

BackgroundMaps can be pre-rendered into "chunks" instead of drawing each tile separately. This speeds up the drawing process immensely, especially on mobile devices. However, the pre-rendered mode needs more RAM and doesn't support tileset animations.


new ig.BackgroundMap( tilesize, data, tileset )



An object specifying the animations for certain tiles. Animations are not updated by the BackgroundMap, but must be updated externally. Usually ig.Game takes care of that – see ig.Game's .backgroundAnims property.

By default, this is an empty object ({}) indicating no animations.

var data = [
var bg = new ig.BackgroundMap( 16, data, 'media/tileset.png' );

// sets tile number 5 of the BackgroundMap to be animated
var as = new ig.AnimationSheet( 'media/tiles.png', 16, 16 );
bg.anims[5] = new ig.Animation( as, 0.1, [0,1,2,3,4] );


The chunk width and height in pixels for pre-rendered BackgroundMaps. The default is 512. See .preRender.

iOS devices seem to support a chunk size of up to 4096, but testing showed no further performance gain with chunk sizes larger than 512.


If .preRender and .debugChunks are true, the .draw() method will draw a pink outline around each chunk.


Distance factor of the BackgroundMap, indicating how fast the Map scrolls when .setScreenPos() is invoked. With a distance of 1, the Map scrolls synchronous to the screen. With a distance of 2 the Map scrolls with half the speed, making it appear farther in the background. The default is 1


New in 1.17

Whether this layer will be drawn in front of all entities. This is set automatically by Weltmeister. The default is false.


If set to true, the next call to .draw() will render the whole background map into chunks of .chunkSize pixels and then use these chunks to draw the map.

Pre-rendered maps can not be animated but are usually drawn much faster than tiled maps.

The default is false.


A Boolean, indicating whether drawing of the Map wraps at the edges. This is useful for secondary BackgroundMaps that are repeated continuously.

.scroll.x, .scroll.y

Scroll position of the BackgroundMap in screen coordinates with the Map's .distance alreday factored in. Should only be read; use .setScreenPos() to set the scroll position of the Map.


An instance of ig.Image representing the Tileset that is used for drawing, as set by the constructor or .setTileset()


Location of the loaded Tileset image (e.g. 'media/tileset.png')



Draws the BackgroundMap at its current .scroll position. If .preRender is true, the map's pre-rendered chunks are drawn, otherwise the map is drawn tile by tile.

.setScreenPos( x, y )

Set the x and y position of the screen. The BackgroundMap's .scroll position will be set acording to its .distance

.setTileset( tileset )

Set a new Tileset. tileset is the location of the image file or instance of ig.Image used as the Tileset.