Tilemap Rendering

've finally added tilemap support for my rendering system:

The performance is so-so: It's more memory and CPU efficient than rendering individual sprites by quite a bit. All you need to do is to specify an image atlas containing all images with power-of-two sizes, ordered in a n x m way. Up to 16x16 maps are supported (though that is rather unlikely due to general memory constraints).

The tilemap itself is a character array where the lower 4 bits are the x coordinate on the tilemap and the higher 4 bits are the y coordinate:

  static unsigned char dataMap[] = {
    0x00, 0x01,0x00,0x02, 0x00, 0x00,0x04,
    0x10, 0x11,0x11,0x10, 0x11, 0x10,0x10,
    0x00, 0x01,0x00,0x03, 0x01, 0x04,0x03,
    0x08, 0x08,0x08,0x08, 0x08, 0x08,0x08,
    0x10, 0x11,0x11,0x10, 0x11, 0x10,0x10,
  };

Using this tileset by surt:

... you should be able to figure this out:

0x00 means (0,0) on the atlas, 0x01 means (0,1), 0x10 means (1,0) and so on.

0xff is a special case to ignore that tile and leave it blank (transparent).

In this case the atlas uses 16x16 tiles and uses a 7x5 tilemap to fill the entire screen.

To draw the tilemap, it must be registered in the render screen structure:

  _renderScreen.tileMap[0].tileSizeXBits = 4;
  _renderScreen.tileMap[0].tileSizeYBits = 4;
  _renderScreen.tileMap[0].dataMapWidth = 7;
  _renderScreen.tileMap[0].dataMapHeight = 5;
  _renderScreen.tileMap[0].dataMap = dataMap;
  _renderScreen.tileMap[0].imageId = 0;

and can then be used in a tilemap draw command:

RenderScreen_drawRectTileMap(screenX,screenY,width,height,tilemapId);

This way you can specify where a tilemap should be drawn, how big it is and of course in which order. This way it should also be possible to use this to draw UIs as well.

The rendering is utilizing 48ms for a 16x16 tileset (bigger renders faster). Drawing some more stuff will raise this number, but this way it's possible to draw levels and have some action on it without making it a slideshow.

I was hoping for some better figures, but the individual image copying actions take its tolls. The code is up on github, as usual.

Fri, 15 May, 2015