bool Intersects(CCRect first, RectWithDirection second)
{
//判断两个rect是否有重叠
return first.UpperRight.X > second.Left &&
first.LowerLeft.X < second.Left + second.Width &&
first.UpperRight.Y > second.Bottom &&
first.LowerLeft.Y < second.Bottom + second.Height;
}
public void PopulateFrom(CCTileMap tileMap)
{
//得到瓦片地图里面的瓦片信息，比如说哪些瓦片可以与entity接触，具体是瓦片的哪个方向的面可以接触
collisions=new List<RectWithDirection> ();
//每个小瓦片的边长加上0.5，这样碰撞时就不会陷进去才弹出
tileDimensionWidth = (int)(tileMap.TileTexelSize.Width + .5f);
tileDimensionHeight = (int)(tileMap.TileTexelSize.Height + .5f);
mBrickLayer = tileMap.LayerNamed ("BrickLayer");
TileMapPropertyFinder finder = new TileMapPropertyFinder (tileMap);
foreach (var propertyLocation in finder.GetPropertyLocations())
{
//如果在这个位置的瓦片是一个固体
if (propertyLocation.Properties.ContainsKey ("SolidCollision"))
{
//worldX worldY 是每个瓦片的中心的坐标
float centerX = propertyLocation.WorldX;
float centerY = propertyLocation.WorldY;
//得到每个小瓦片的左边界和下边界
float left = centerX - tileDimensionWidth/2.0f;
float bottom = centerY - tileDimensionHeight/2.0f;
//在那个点构造一个小瓦片
RectWithDirection rectangle = new RectWithDirection {
Left = left,
Bottom = bottom,
Width = tileDimensionWidth,
Height = tileDimensionHeight,
tiledMapCoordinate=propertyLocation.TileCoordinates
};
//得到地图上所有的固体小块
collisions.Add (rectangle);
}
}
// Sort by XAxis to speed future searches:
//collisions是把整个瓦片地图按每个瓦片的左边的坐标进行排序的list
//在每一个左边坐标有一列的瓦片
//debug看一下
collisions = collisions.OrderBy(item=>item.Left).ToList();
// now let's adjust the directions that these point
//调整每个小块的角度
for (int i = 0; i < collisions.Count; i++)
{
var rect = collisions [i];
// By default rectangles can reposition objects in all directions:
int valueToAssign = (int)Directions.All; //15
float centerX = rect.CenterX;
float centerY = rect.CenterY;
// If there are collisions on the sides, then this
// rectangle can no longer repositon objects in that direction.
// 一开始小瓦片的方向valueToAssign可能是所有的方向，每次减去一种不可能的方向值，最后得到的就是正确的方向的值的和
//direction是这个实体瓦片暴露在外，可以与entity接触的方向
//比如说瓦片地图里的地面，方向就为up
if (HasCollisionAt (centerX - tileDimensionWidth, centerY))
{
valueToAssign -= (int)Directions.Left;
}
if (HasCollisionAt (centerX + tileDimensionWidth, centerY))
{
valueToAssign -= (int)Directions.Right;
}
if (HasCollisionAt (centerX, centerY + tileDimensionHeight))
{
valueToAssign -= (int)Directions.Up;
}
if (HasCollisionAt (centerX, centerY - tileDimensionHeight))
{
valueToAssign -= (int)Directions.Down;
}
rect.Directions = (Directions)valueToAssign;
//更新瓦片列表中的瓦片的方向
collisions [i] = rect;
}
for (int i = collisions.Count - 1; i > -1; i--)
{
//经过筛选后，遍历删除那些没有方向的瓦片
if (collisions [i].Directions == Directions.None)
{
collisions.RemoveAt (i);
}
}
}
List<CCVector2> GetSeparatingVector(CCRect first, RectWithDirection second)
{
//返回一个向量，是player在碰撞之后反方向移动的向量
List<CCVector2> separation = new List<CCVector2> {
CCVector2.Zero,
CCVector2.Zero,
CCVector2.Zero,
CCVector2.Zero
};
// Only calculate separation if the rectangles intersect
if (Intersects(first, second))
{
// The intersectionRect returns the rectangle produced
// by overlapping the two rectangles.
// This is protected by partitioning and deep collision, so it
// won't happen too often - it's okay to do a ToRect here
//得到两个rect重叠部分的rect
var intersectionRect = first.Intersection (second.ToRect());
float minDistance = float.PositiveInfinity;
float firstCenterX = first.Center.X;
float firstCenterY = first.Center.Y;
float secondCenterX = second.Left + second.Width / 2.0f;
float secondCenterY = second.Bottom + second.Height / 2.0f;
//second的方向和想要判断的方向（左）取交集，如果和想要判断的方向（左）一致，且第一个的中心点在第二个的中心点的（左边）
//则当碰撞时，player可以向想要的方向移动
bool canMoveLeft = (second.Directions & Directions.Left) == Directions.Left && firstCenterX < secondCenterX;
bool canMoveRight = (second.Directions & Directions.Right) == Directions.Right && firstCenterX > secondCenterX;
bool canMoveDown = (second.Directions & Directions.Down) == Directions.Down && firstCenterY < secondCenterY;
bool canMoveUp = (second.Directions & Directions.Up) == Directions.Up && firstCenterY > secondCenterY;
if (canMoveLeft)
{
//左重叠
//得到重叠的rect的X方向边长
float candidate = first.UpperRight.X - second.Left;
if (candidate > 0)
{
minDistance = candidate;
//x方向移动回到地图实体瓦片的外面，y方向不动
separation [0] = new CCVector2 (-minDistance, 0);
}
}
if (canMoveRight)
{
//右重叠
float candidate = (second.Left + second.Width) - first.LowerLeft.X;
if (candidate > 0)
{
minDistance = candidate;
//向右移动
separation [1] = new CCVector2 (minDistance, 0);
}
}
//其他方向同理
if (canMoveUp)
{
float candidate = (second.Bottom + second.Height) - first.Origin.Y;
if (candidate > 0)
{
minDistance = candidate;
separation [2] = new CCVector2 (0, minDistance);
}
}
if (canMoveDown)
{
float candidate = first.UpperRight.Y - second.Bottom;
if (candidate > 0)
{
minDistance = candidate;
separation [3] = new CCVector2 (0, -minDistance);
}
}
if ((intersectionRect.UpperRight.X > (second.Left + first.Size.Width))
&& (intersectionRect.LowerLeft.X < (second.Left + second.Width - first.Size.Width))) {
separation [0] = new CCVector2 (0, 0);
separation [1] = new CCVector2 (0, 0);
}
}
//左后返回player移动的vector
return separation;
}