下面是一個(gè)旋轉(zhuǎn)的動(dòng)力皮蒙克物體，里面有一個(gè)質(zhì)量。動(dòng)畫開始播放后，有沒有辦法獲取“body_type”頂部水平部分的中點(diǎn)。最初，我感興趣的動(dòng)體上的點(diǎn)的坐標(biāo)為 (400,500)。旋轉(zhuǎn)開始后如何打印相關(guān)點(diǎn)的更新坐標(biāo)import pymunkimport pymunk.pygame_utilimport pygameGRAY = (220, 220, 220)width_mass=50height_mass=50pygame.init()size = 800,600screen = pygame.display.set_mode(size)draw_options = pymunk.pygame_util.DrawOptions(screen)space = pymunk.Space()space.gravity = (0,-50)pts = [(-27, -238.5), (27,-238.5), (27,238.5), (-27,238.5)]body_type=pymunk.Body(body_type=pymunk.Body.KINEMATIC) body_type.position = (400, 263.5) space.add(body_type)for i in range(4): segment = pymunk.Segment(body_type, pts[i], pts[(i+1)%4], 2) segment.elasticity = 0 segment.friction=0 space.add(segment)body_type.angular_velocity=1body = pymunk.Body(mass=1, moment=100)body.position = 400,400mass = pymunk.Poly.create_box(body, (width_mass, height_mass))mass.elasticity = 0space.add(body, mass)running = Truewhile running: for event in pygame.event.get(): if event.type == pygame.QUIT: running = False #pygame.image.save(screen, 'intro1.png') screen.fill(GRAY) space.debug_draw(draw_options) pygame.display.update() space.step(0.01)
2 回答
湖上湖
TA貢獻(xiàn)2003條經(jīng)驗(yàn) 獲得超2個(gè)贊
a 的當(dāng)前位置Body存儲(chǔ)在position屬性中（例如space.bodies[0].position）。
PyGame 使用左上角為 (0, 0) 的坐標(biāo)系。y 軸需要反轉(zhuǎn) (?screen.get_height() - pos[1])，因?yàn)?y 軸一般指向上，但在 PyGame 坐標(biāo)系中 y 軸指向下。
running = True
while running:
? ? # [...]
? ? # draw a dot in at the center of the bodies
? ? for body in space.bodies:
? ? ? ? pos = body.position
? ? ? ? pygame.draw.circle(screen, (255,0,0), (pos[0], screen.get_height()-pos[1]), 7)
? ? pygame.display.update()
? ? space.step(0.01)
a 的當(dāng)前角度Body存儲(chǔ)在angle屬性中（例如body_type.angle）。
可以通過將旋轉(zhuǎn)的相對(duì)位置與絕對(duì)位置相加來計(jì)算點(diǎn)的當(dāng)前位置。旋轉(zhuǎn)位置可以通過簡(jiǎn)單的三角函數(shù)計(jì)算：
pos?=?abs_pos[0]?+?rel_dist?*?math.cos(angle),?abs_pos[1]?+?rel_dist?*?math.sin(angle)
首先，您必須根據(jù)相對(duì)笛卡爾坐標(biāo)計(jì)算相對(duì)極坐標(biāo)：
rel_pos?=?(0,?238.5) rel_dist,?rel_angle?=?math.hypot(*rel_pos),?math.atan2(rel_pos[1],?rel_pos[0])
將當(dāng)前角度添加到極坐標(biāo)角度：
angle?=?rel_angle?+?body_type.angle
例如：
running = True
while running:
? ? # [...]
? ? abs_pos = body_type.position
? ? rel_pos = (0, 238.5)
? ? rel_dist, rel_angle = math.hypot(*rel_pos), math.atan2(rel_pos[1], rel_pos[0])
? ??
? ? angle = rel_angle + body_type.angle
? ? pos = abs_pos[0] + rel_dist * math.cos(angle), abs_pos[1] + rel_dist * math.sin(angle)
? ? pygame.draw.circle(screen, (255, 255, 0), (pos[0], screen.get_height() - pos[1]), 7)
? ? pygame.display.update()
? ? space.step(0.01)
最小的例子：
import pymunk
import pymunk.pygame_util
import pygame
import math
GRAY = (220, 220, 220)
width_mass=50
height_mass=50
pygame.init()
size = 800,600
screen = pygame.display.set_mode(size)
draw_options = pymunk.pygame_util.DrawOptions(screen)
space = pymunk.Space()
space.gravity = (0,-50)
pts = [(-27, -238.5), (27,-238.5), (27,238.5), (-27,238.5)]
body_type=pymunk.Body(body_type=pymunk.Body.KINEMATIC)??
body_type.position = (400, 263.5)??
space.add(body_type)
for i in range(4):
? ? segment = pymunk.Segment(body_type, pts[i], pts[(i+1)%4], 2)
? ? segment.elasticity = 0
? ? segment.friction=0
? ? space.add(segment)
body_type.angular_velocity=0.5
body = pymunk.Body(mass=1, moment=100)
body.position = 400,400
mass = pymunk.Poly.create_box(body, (width_mass, height_mass))
mass.elasticity = 0
space.add(body, mass)
running = True
while running:
? ? for event in pygame.event.get():
? ? ? ? if event.type == pygame.QUIT:
? ? ? ? ? ? running = False
? ? ? ? ? ? #pygame.image.save(screen, 'intro1.png')
? ? screen.fill(GRAY)
? ? space.debug_draw(draw_options)
? ? for body in space.bodies:
? ? ? ? pos = body.position
? ? ? ? pygame.draw.circle(screen, (255, 0, 0), (pos[0], screen.get_height() - pos[1]), 7)
? ? abs_pos = body_type.position
? ? rel_pos = (0, 238.5)
? ? rel_dist, rel_angle = math.hypot(*rel_pos), math.atan2(rel_pos[1], rel_pos[0])
? ? angle = rel_angle + body_type.angle
? ? print( body_type.position.angle)
? ? pos = abs_pos[0] + rel_dist * math.cos(angle), abs_pos[1] + rel_dist * math.sin(angle)
? ? pygame.draw.circle(screen, (255, 255, 0), (pos[0], screen.get_height() - pos[1]), 7)
? ? pygame.display.update()
? ? space.step(0.01)
汪汪一只貓
TA貢獻(xiàn)1898條經(jīng)驗(yàn) 獲得超8個(gè)贊
使 Pymunk 模擬的行為類似于本機(jī) PyGame 坐標(biāo)。您只需將以下行添加到您的代碼中即可。
pygame.pygame_util.positive_y_is_up = True
自 PyMunk 6.0 起已默認(rèn)為 True。
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