Which will used cache the bitmap index the current tile

140 5. Multi-Dimensional Arrays

1: void DrawTilemap( int p_x, int p_y )
2: {
3: int x, y, z;
4: int bx = p_x;
5: int by = p_y;
6: int index;
7: for( z = 0; z < LAYERS; z++ )
8: {
9: bx = p_x;
10: by = p_y;
11: for( y = 0; y < MAPHEIGHT; y++ )
12: {
13: for( x = 0; x < MAPWIDTH; x++ )
14: {
15: index = g_tilemap.Get( x, y, z );
16: if( index != -1 )
17: {
18: SDLBlit( g_tiles[index], g_window, bx, by ); 19: }
20: bx += TILESIZE;
21: }
22: bx = p_x;
23: by += TILESIZE;
24: }
25: }
26: }

Team LRN

The outermost loop, starting on line 7, loops through each layer, starting with the base layer. Every time a new layer is started, the loop resets bx and by to the original values because each layer is drawn directly on top of the previous layer.

Starting at line 15, I determine if the tile should be drawn and then draw it. In the first tilemap demonstration, I assumed that every tile will be a valid tile. However, I cannot do that this time, because many of the tiles on some of the layers might be �1, which is invalid. So on line 15, I get the index of the current tile, and if it isn’t invalid, I continue to draw it. If it is invalid, I don’t draw anything.

Figure 5.15

This is a screenshot
from the Layered
Tilemap demo.