求45度tiled地图坐标的计算原理讲解

Cocos2d-x
#1
  • 本帖最后由 osmanthus 于 2012-12-5 17:07 编辑 *

求45度tiled地图坐标的计算原理讲解,
看了个OC的源码,没有搞清楚其中的原理, 求解惑:









-(CGPoint) tilePosFromLocation:(CGPoint)location tileMap:(CCTMXTiledMap*)tileMap
{
    // Tilemap position must be subtracted, in case the tilemap position is scrolling
    CGPoint pos = ccpSub(location, tileMap.position);
    
    float halfMapWidth = tileMap.mapSize.width * 0.5f;
    float mapHeight = tileMap.mapSize.height;
    float tileWidth = tileMap.tileSize.width;
    float tileHeight = tileMap.tileSize.height;
    
    CGPoint tilePosDiv = CGPointMake(pos.x / tileWidth, pos.y / tileHeight);
    float inverseTileY = mapHeight - tilePosDiv.y;
    
    // Cast to int makes sure that result is in whole numbers
    float posX = (int)(inverseTileY + tilePosDiv.x - halfMapWidth);
    float posY = (int)(inverseTileY - tilePosDiv.x + halfMapWidth);
    
    // make sure coordinates are within isomap bounds
    posX = MAX(0, posX);
    posX = MIN(tileMap.mapSize.width - 1, posX);
    posY = MAX(0, posY);
    posY = MIN(tileMap.mapSize.height - 1, posY);
    
    return CGPointMake(posX, posY);
}

posX, posY为什么要如此求解?

多谢!