Pygame，RPG游戏的有效碰撞处理？

Question

我目前正在使用 pygame 编写一个类似 Snes 的小角色扮演游戏。
在我的地图上，我有 4 层：
0：地形，无碰撞（在字符下）
1：在地形上没有碰撞（在字符下）
2：碰撞对象（char下）
3：超过 char 对象

我想为我的第二层中的每个图块创建一个矩形，以防止角色越过这些对象。有没有一种有效的方法可以在每次角色移动时不检查每个矩形？谢谢。

Answer 1

pygame 有很多为此优化的函数，比如Rect.collidelist:

collidelist()
测试列表中的一个矩形是否相交

collidelist(list) -> 索引

测试矩形是否与矩形序列中的任何一个碰撞。返回找到的第一个碰撞的索引。如果没有发现冲突，则返回 -1 的索引。

如果您仍然遇到性能问题，您可以使用QuadTree。

Here's an implementation in python using pygame.

from pygame import Rect

class QuadTree(object):
    """An implementation of a quad-tree.

    This QuadTree started life as a version of [1] but found a life of its own
    when I realised it wasn't doing what I needed. It is intended for static
    geometry, ie, items such as the landscape that don't move.

    This implementation inserts items at the current level if they overlap all
    4 sub-quadrants, otherwise it inserts them recursively into the one or two
    sub-quadrants that they overlap.

    Items being stored in the tree must be a pygame.Rect or have have a
    .rect (pygame.Rect) attribute that is a pygame.Rect
        ...and they must be hashable.

    Acknowledgements:
    [1] http://mu.arete.cc/pcr/syntax/quadtree/1/quadtree.py
    """

    def __init__(self, items, depth=8, bounding_rect=None):
        """Creates a quad-tree.

        @param items:
            A sequence of items to store in the quad-tree. Note that these
            items must be a pygame.Rect or have a .rect attribute.

        @param depth:
            The maximum recursion depth.

        @param bounding_rect:
            The bounding rectangle of all of the items in the quad-tree. For
            internal use only.
        """

        # The sub-quadrants are empty to start with.
        self.nw = self.ne = self.se = self.sw = None

        # If we've reached the maximum depth then insert all items into this
        # quadrant.
        depth -= 1
        if depth == 0 or not items:
            self.items = items
            return

        # Find this quadrant's centre.
        if bounding_rect:
            bounding_rect = Rect( bounding_rect )
        else:
            # If there isn't a bounding rect, then calculate it from the items.
            bounding_rect = Rect( items[0] )
            for item in items[1:]:
                bounding_rect.union_ip( item )
        cx = self.cx = bounding_rect.centerx
        cy = self.cy = bounding_rect.centery

        self.items = []
        nw_items = []
        ne_items = []
        se_items = []
        sw_items = []

        for item in items:
            # Which of the sub-quadrants does the item overlap?
            in_nw = item.rect.left <= cx and item.rect.top <= cy
            in_sw = item.rect.left <= cx and item.rect.bottom >= cy
            in_ne = item.rect.right >= cx and item.rect.top <= cy
            in_se = item.rect.right >= cx and item.rect.bottom >= cy

            # If it overlaps all 4 quadrants then insert it at the current
            # depth, otherwise append it to a list to be inserted under every
            # quadrant that it overlaps.
            if in_nw and in_ne and in_se and in_sw:
                self.items.append(item)
            else:
                if in_nw: nw_items.append(item)
                if in_ne: ne_items.append(item)
                if in_se: se_items.append(item)
                if in_sw: sw_items.append(item)

        # Create the sub-quadrants, recursively.
        if nw_items:
            self.nw = QuadTree(nw_items, depth, (bounding_rect.left, bounding_rect.top, cx, cy))
        if ne_items:
            self.ne = QuadTree(ne_items, depth, (cx, bounding_rect.top, bounding_rect.right, cy))
        if se_items:
            self.se = QuadTree(se_items, depth, (cx, cy, bounding_rect.right, bounding_rect.bottom))
        if sw_items:
            self.sw = QuadTree(sw_items, depth, (bounding_rect.left, cy, cx, bounding_rect.bottom))


    def hit(self, rect):
        """Returns the items that overlap a bounding rectangle.

        Returns the set of all items in the quad-tree that overlap with a
        bounding rectangle.

        @param rect:
            The bounding rectangle being tested against the quad-tree. This
            must possess left, top, right and bottom attributes.
        """

        # Find the hits at the current level.
        hits = set( [ self.items[n] for n in rect.collidelistall( self.items ) ] )

        # Recursively check the lower quadrants.
        if self.nw and rect.left <= self.cx and rect.top <= self.cy:
            hits |= self.nw.hit(rect)
        if self.sw and rect.left <= self.cx and rect.bottom >= self.cy:
            hits |= self.sw.hit(rect)
        if self.ne and rect.right >= self.cx and rect.top <= self.cy:
            hits |= self.ne.hit(rect)
        if self.se and rect.right >= self.cx and rect.bottom >= self.cy:
            hits |= self.se.hit(rect)

        return hits

与在简单循环中检查每个图块相比，这将大大提高性能。

Answer 2

您可以使用recs 并检查它们是否像 Dominic Kexel 所说的那样发生碰撞，但是如果您的图形不完全是正方形并且碰撞检测需要完美，我建议使用带有 pygame 掩码的 pygame sprite 对象.可以根据 alpha 值（透明度）设置遮罩，并且非常容易处理：

class Entity(pygame.sprite.Sprite):
    def __init__(self, image): #where image is a pygame image with that has had the convert_alpha() function used on it
        self.image = image
        self.rect = image.get_rect() #you can use a rect and a mask
        self.mask = pygame.mask.from_surface(self.image) #creates a mask from the image ans assigns it to the sprite object

然后您可以使用rect 属性轻松检查碰撞（您可以使用矩形处理各种不同类型的碰撞），或者您可以使用遮罩检查像素完美碰撞。

任何这些都可以使用 pygames sprite 碰撞函数来完成，例如 pygame.sprite.spritecollide() 或 pygame.sprite.collide_mask() + 更多！

阅读：

http://www.pygame.org/docs/ref/sprite.html

http://www.pygame.org/docs/ref/mask.html

http://www.pygame.org/docs/ref/rect.html