多次碰撞未测试

Question

我有一个 box2d pygame 平台示例。您可以移动玩家并生成平台。除非玩家与关卡中的所有平台发生碰撞，否则我无法对玩家执行跳跃动作。这不是有意为之的行为，我们希望的是能够在您触摸一个平台而不是所有其他平台时跳跃。我正在使用 for 循环遍历播放器的所有碰撞，并根据需要设置 can_jump。

main.py

import pygame
from draw import Draw
from Box2D import (b2World,b2Vec2)

from box import Box

from player import Player

def Run():
    PPM = 20
    TARGET_FPS = 60
    TIME_STEP = 1.0 / TARGET_FPS

    SCREEN_WIDTH,SCREEN_HEIGHT = 640,480
    CAPTION = ""

    BGCOLOR = ((255,255,255))

    pygame.init()
    screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
    pygame.display.set_caption(CAPTION)
    clock = pygame.time.Clock()

    world = b2World(gravity=(0, 30), doSleep=True)

    closed = False

    global player, hold_left, hold_right, can_jump, speed, deceleration
    player = Player(world,200,200,PPM)
    speed = 20
    deceleration = 0.95
    hold_left = False
    hold_right = False
    can_jump = False

    while not closed:

        def left():
            player.body.ApplyForce(b2Vec2(-1*speed*speed,0),point=player.body.worldCenter,wake=True)
        def right():
            player.body.ApplyForce(b2Vec2(speed*speed,0),point=player.body.worldCenter,wake=True)
        if hold_left:
            left()
        elif hold_right:
            right()

        if len(player.body.contacts) == 0:
            can_jump = False
        else:
            for contact in player.body.contacts:
                contact = contact.contact
                print(contact)
                if contact.manifold.localPoint == b2Vec2(0,1):
                    can_jump=True
                elif contact.manifold.localPoint != b2Vec2(0,1):
                    can_jump=False

        for event in pygame.event.get():
            if event.type == pygame.QUIT: 
                closed = True
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_d:
                    hold_right = True
                elif event.key == pygame.K_a:
                    hold_left = True
                elif event.key == pygame.K_SPACE:
                    if can_jump:
                        player.body.linearVelocity.y = 0
                        player.body.ApplyLinearImpulse(b2Vec2(0,-150),point=player.body.worldCenter,wake=True)
            if event.type == pygame.KEYUP:
                if event.key == pygame.K_d:
                    hold_right = False
                elif event.key == pygame.K_a:
                    hold_left = False

        click = pygame.mouse.get_pressed()  
        if click[0] == 1:
            x,y = pygame.mouse.get_pos()
            Box(world, x, y, PPM)

        player.body.linearVelocity.x *= deceleration

        screen.fill(BGCOLOR)

        Draw(screen,world.bodies,PPM)

        world.Step(TIME_STEP, 10, 10)
        pygame.display.flip()
        clock.tick(TARGET_FPS)

    pygame.quit()

if __name__ == '__main__':
    Run()

player.py

from Box2D import (b2FixtureDef, b2PolygonShape)

class Player:
    def __init__(self, world, x, y, PPM):
        self.x = x / PPM
        self.y = y / PPM
        self.w = 1
        self.h = 1
        self.gh = 0.1

        self.world = world
        self.body = self.world.CreateDynamicBody(
            position=(self.x, self.y),
            fixtures=b2FixtureDef(
                shape=b2PolygonShape(box=(self.w, self.h)), density=2.0, friction = 0.1))
        self.body.fixedRotation = True

box.py

from Box2D import (b2FixtureDef, b2PolygonShape)

class Box:
    def __init__(self, world, x, y, PPM):
        self.x = x / PPM
        self.y = y / PPM
        self.w = 10
        self.h = 1

        self.world = world
        self.body = self.world.CreateStaticBody(
            position=(self.x, self.y),
            fixtures=b2FixtureDef(
                shape=b2PolygonShape(box=(self.w, self.h)), density=2.0, friction = 0.1))

draw.py

import pygame
from Box2D import b2PolygonShape

def Poly(screen,body,fixture,PPM):
    shape = fixture.shape
    vertices = [(body.transform * v) * PPM for v in shape.vertices]
    pygame.draw.polygon(screen, (0, 255, 187), vertices)
    pygame.draw.polygon(screen, (0,0,0), vertices,2)

def Draw(screen,bodies,PPM):
    for body in bodies:
        for fixture in body.fixtures:
            if isinstance(fixture.shape, b2PolygonShape):
                Poly(screen,body,fixture,PPM)

Answer 1

您几乎可以肯定这部分代码存在逻辑错误，它似乎控制了您的布尔 can_jump 变量：

else:
    for contact in player.body.contacts:
        contact = contact.contact
        print(contact)
        if contact.manifold.localPoint == b2Vec2(0,1):
            can_jump=True
        elif contact.manifold.localPoint != b2Vec2(0,1):
            can_jump=False

一个错误、一个清理和一些提示...

首先是错误：

您正在循环浏览联系人。当你跳出这个循环时，是什么决定了 can_jump 的 T/F 值？

Ans：只有数据容器中的最后一个联系人会影响can_jump的值。这有意义吗？

提示：

您在这里测试 T/F 条件，正确的方法是测试一次并让其确定结果。现在您正在测试“如果为真”，然后测试“如果为假”。这是多余的并且容易出错。所以像这样更好：

if contact.blah.blah == b2vec():
    can_jump = True
else:
    can_jump = False

更正：

现在，这并不能解决您的问题。（这与您的代码一样长...大声笑）。您可能想要做的是检查“所有”或“任何”联系人以确定条件，具体取决于您的游戏逻辑。您可以像现在一样使用循环来执行此操作，并且如果您遇到“失败”条件，则设置变量并跳出循环等。或者你可以熟练地看看Python的any()和all()内置命令。

例如...（您可以将此处的逻辑测试替换为您自己的，但这显示了结构）

contacts = {2, 5, 7}

can_jump = any(contact > 3 for contact in contacts)
print(can_jump)  # True

can_jump = all(contact > 3 for contact in contacts)
print(can_jump)  # False

因此，您可以正确地重新编写循环逻辑，也可以将其全部替换为 1 行代码，即使 contacts 为空，它也应该可以工作，这也会生成 False！

多次碰撞未测试

Multiple collisions not testing

python

pygame

collision

game-physics

首先是错误：

提示：

更正：