谁能告诉我一个使用 Vector2.as_polar()
的例子吗?获取距离和方位角,然后将该信息插入 Vector2.from_polar()
以获得笛卡尔坐标?
假设我们需要 (0, 0)
和 (15, 10)
之间的距离和方位角,然后将该信息插入 Vector2。 from_polar()
再次生成 (15, 10)
。
我会准确地解释我在做什么,但对于我和其他人来说,只看一个工作示例可能会更容易。
最佳答案
您可以将矢量定义为半径和角度 - 极坐标。
让我们使用屏幕中心的点向量作为极坐标系的极点。
pole = Vector2(screen_rect.center)
要借助 from_polar
方法设置向量的坐标,首先定义一个向量,然后传递一个由半径和角度组成的元组:
vec = Vector2()
# This updates the cartesian coordinates of vec.
vec.from_polar((90, 60)) # 90 pixels long, rotated 60 degrees.
然后使用pygame.draw.line
绘制它(将vec
添加到pole
以获得目标坐标):
pg.draw.line(screen, (200, 90, 20), pole, pole+vec, 3)
作为 as_polar
的演示,计算鼠标位置的矢量并将极坐标解包到我们的变量 r
和 phi
中稍后渲染以查看此矢量的当前半径和角度。
r, phi = (mouse_pos-pole).as_polar()
请注意,pygame 的 y 轴是翻转的,因此负角指向上方,正角指向下方。
import sys
import pygame as pg
from pygame.math import Vector2
def main():
screen = pg.display.set_mode((640, 480))
screen_rect = screen.get_rect()
font = pg.font.Font(None, 30)
color = pg.Color(150, 250, 100)
clock = pg.time.Clock()
pole = Vector2(screen_rect.center)
# A zero vector.
vec = Vector2()
# To set the coordinates of `vec` we can pass the
# polar coordinates (radius, angle) to `from_polar`.
vec.from_polar((90, 60))
print(vec) # Now take a look at the updated cartesian coordinates.
done = False
while not done:
for event in pg.event.get():
if event.type == pg.QUIT:
done = True
mouse_pos = pg.mouse.get_pos()
# `as_polar` gives us the radius and angle of the vector that
# points to the mouse. Unpack it into the `r` and `phi` variables.
r, phi = (mouse_pos-pole).as_polar()
screen.fill((30, 30, 30))
# Draw the line to the mouse pos.
pg.draw.line(screen, color, pole, mouse_pos, 3)
# Add the vec to the pole to get the target coordinates.
pg.draw.line(screen, (200, 90, 20), pole, pole+vec, 3)
# Render the radius and angle.
txt = font.render('r: {:.1f}'.format(r), True, color)
screen.blit(txt, (30, 30))
txt = font.render('phi: {:.1f}'.format(phi), True, color)
screen.blit(txt, (30, 50))
pg.display.flip()
clock.tick(30)
if __name__ == '__main__':
pg.init()
main()
pg.quit()
sys.exit()
这是另一个示例, Sprite 跟随鼠标(按“w”或“s”加速)。我将 self.speed
作为半径和角度传递给 as_polar
作为参数返回给 from_polar
以设置 vel
玩家 Sprite 的城市。
import sys
import pygame as pg
class Player(pg.sprite.Sprite):
def __init__(self, pos):
super().__init__()
self.image = pg.Surface((50, 30), pg.SRCALPHA)
color = pg.Color('dodgerblue1')
pg.draw.polygon(self.image, color, ((1, 1), (49, 15), (1, 29)))
self.orig_img = self.image
self.rect = self.image.get_rect(center=pos)
self.pos = pg.math.Vector2(pos)
self.vel = pg.math.Vector2(0, 0)
self.speed = 0
def update(self):
self.rotate()
self.pos += self.vel
self.rect.center = self.pos
def rotate(self):
_, angle = (pg.mouse.get_pos()-self.pos).as_polar()
self.vel.from_polar((self.speed, angle))
self.image = pg.transform.rotozoom(self.orig_img, -angle, 1)
self.rect = self.image.get_rect(center=self.rect.center)
def main():
screen = pg.display.set_mode((640, 480))
clock = pg.time.Clock()
all_sprites = pg.sprite.Group()
player = Player((300, 200))
all_sprites.add(player)
done = False
while not done:
for event in pg.event.get():
if event.type == pg.QUIT:
done = True
keys = pg.key.get_pressed()
if keys[pg.K_w]:
player.speed += .2
elif keys[pg.K_s]:
player.speed -= .2
all_sprites.update()
screen.fill((30, 30, 30))
all_sprites.draw(screen)
pg.display.flip()
clock.tick(30)
if __name__ == '__main__':
pg.init()
main()
pg.quit()
sys.exit()
关于python - Pygame Vector2.as_polar() 和 Vector2.from_polar() 方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45420223/