修复 Box2D 绘图

Question

我正在尝试绘制一个矩形，它的每边都有一条边（它应该代表一个带有围栏的建筑物）对于一个建筑物来说效果很好，但是当我试图添加一个新的构建它完全搞砸了。

我有创建建筑物的代码：

class Building():
    def __init__(self, Box_2_World,shape, position, sensor= None):
        self.Box_2_World = Box_2_World
        self.shape = shape
        self.position = position

        if sensor == None:
            sensor = False

        self.sensor = sensor
        self.footprint = self.Box_2_World.CreateStaticBody(position = position,
                                                           angle = 0.0,
                                                           fixtures = b2FixtureDef(
                                                               shape = b2PolygonShape(box=(self.shape)),
                                                               density = 1000,
                                                               friction = 1000))

        self.Lower_Fence = self.Box_2_World.CreateStaticBody(position=(self.footprint.position[0],self.footprint.position[1] -1.75*self.shape[1]))
        self.Lower_Fence.CreateEdgeChain([(self.Lower_Fence.position[0]-4.25*self.shape[0],self.Lower_Fence.position[1]),
                            (self.Lower_Fence.position[0]-2.25*self.shape[0],self.Lower_Fence.position[1]),
                        ])

        self.Right_Fence = self.Box_2_World.CreateStaticBody(position=(self.footprint.position[0]-1*self.shape[0],self.footprint.position[1]))
        self.Right_Fence.CreateEdgeChain([(self.Right_Fence.position[0],self.Right_Fence.position[1] - 1.25*self.shape[1]),
                            (self.Right_Fence.position[0],self.Right_Fence.position[1]-3.25*self.shape[1]),
                        ])

        self.Upper_Fence = self.Box_2_World.CreateStaticBody(position=(self.footprint.position[0],self.footprint.position[1] -0.45* self.shape[1]))
        self.Upper_Fence.CreateEdgeChain([(self.Upper_Fence.position[0] - 4.25* self.shape[0],self.Upper_Fence.position[1]),
                            (self.Upper_Fence.position[0]- 3.25* self.shape[0]+ self.shape[0],self.Upper_Fence.position[1]),
                        ])

        self.Left_Fence = self.Box_2_World.CreateStaticBody(position=(self.footprint.position[0]-2.25*self.shape[0],self.footprint.position[1]))
        self.Left_Fence.CreateEdgeChain([(self.Left_Fence.position[0],self.Left_Fence.position[1] - 1.25*self.shape[1]),
                            (self.Left_Fence.position[0],self.Left_Fence.position[1]-3*self.shape[1]),
                        ])

Skyscrapers = []
Rectangles = [(pos_X-5, pos_Y-5),(pos_X+15, pos_Y -5),(pos_X - 5,pos_Y + 15),(pos_X+15, pos_Y + 15)]

for i in range(4):
    Skyscrapers.append(Building(Box_2_World,shape = (5,5), position =  Rectangles[i]))

以及使用这些函数绘制它 PyGame:

SCREEN_OFFSETX, SCREEN_OFFSETY = SCREEN_WIDTH/16, SCREEN_HEIGHT

def fix_vertices(vertices):
    return [(int(SCREEN_OFFSETX + v[0]), int(SCREEN_OFFSETY - v[1])) for v in vertices]
def _draw_polygon(polygon, screen, body, fixture):
    transform = body.transform
    vertices = fix_vertices([transform * v * PPM for v in polygon.vertices])
    pygame.draw.polygon(
        screen, [c / 2.0 for c in colors[body.type]], vertices, 0)
    pygame.draw.polygon(screen, colors[body.type], vertices, 1)
polygonShape.draw = _draw_polygon

def _draw_edge(edge, screen, body, fixture):
    vertices = fix_vertices(
        [body.transform * edge.vertex1 * PPM, body.transform * edge.vertex2 * PPM])
    pygame.draw.line(screen, colors[body.type], vertices[0], vertices[1])
edgeShape.draw = _draw_edge

输出是这样的：蓝色矩形代表建筑物，蓝线是栅栏，第一个建筑物非常适合，但其他建筑物由于某种原因超出了预期的位置

此外，如果您找到一种使用 for 循环创建围栏的方法，那就太好了（这就是我将 for-loop 标记放入此问题的原因）

感谢任何帮助

Answer 1

传递给 CreateEdgeChain 的坐标必须相对于 body。

body的位置是在构造object时设置的，例如：

self.Lower_Fence = self.Box_2_World.CreateStaticBody(
    position=(self.footprint.position[0], self.footprint.position[1] -1.75*self.shape[1]))

并且边缘必须相对于此位置而不是绝对 position.e.g:

self.Lower_Fence.CreateEdgeChain([(-4.25*self.shape[0], 0), (-2.25*self.shape[0], 0)])

要在 for 循环中创建围栏，您必须定义一个边列表。使用边缘列表，您可以创建栅栏列表：

fence_edges = [
    [(-4.25, -1.75), (-2.25, -1.75)],
    [(-1.00, -1.25), (-1.00, -3.25)],
    [(-4.25, -0.45), (-2.25, -0.45)],
    [(-2.25, -1.25), (-2.25, -3.25)]
]

self.Fences = []
for edge in fence_edges:
    p1, p2 = edge
    fence = self.Box_2_World.CreateStaticBody(position=self.footprint.position[:])
    fence.CreateEdgeChain(
        [(p1[0] * self.shape[0], p1[1] * self.shape[1]),
         (p2[0] * self.shape[0], p2[1] * self.shape[1])])
    self.Fences.append(fence)

self.Lower_Fence, self.Right_Fence, self.Upper_Fence, self.Left_Fence = self.Fences

修复 Box2D 绘图

Fixing Box2D Drawings

python

pygame

for-loop

box2d