在pygame中用圆周上的点创建一个圆

Question

我希望在 pygame 中创建一个圆圈，我可以在边缘带有“传感器”的空间中移动。我希望圆周上有一个“前”、“左”和“右”传感器，我可以用它来操纵圆的运动。

基本上，这些点是为了帮助检测周围的障碍物，并允许圆圈在移动时旋转（以帮助控制移动）。

在下图中你可以看到这个想法，圆圈从一个位置开始，有指针，在空间中移动并避开方形障碍物，我可以在不同的角度转动它而不会失去感觉它的“前”和“后”是什么。

我不在乎圆圈边缘上用于识别“传感器”的点是否在整体图形中看到，只是绘制并标记它们以说明这个想法。

旁注：我意识到看着图像，考虑到圆本身的方向，R 和 L 标签是向后的，但仍然是相同的想法。

Answer 1

您可以为这三个点定义一些vectors。如果你用圆的半径创建一个向量并将它添加到中心坐标，你会在圆周上得到一个点。然后您可以将此向量旋转 -90 度和 90 度以获得另外两个向量。当agent旋转时，可以先旋转前面的向量，然后再用它得到左右向量。

这是一个完整的例子：

import pygame as pg
from pygame.math import Vector2


class Agent(pg.sprite.Sprite):

    def __init__(self, pos, *groups):
        super(Agent, self).__init__(*groups)
        self.radius = 25
        self.image = pg.Surface((50, 50), pg.SRCALPHA)
        pg.draw.circle(self.image, pg.Color('dodgerblue4'),
                       (self.radius, self.radius), self.radius)
        self.rect = self.image.get_rect(center=pos)
        self.speed = 0
        self.angular_speed = 0
        self.pos = Vector2(pos)
        # If you add this vector to the center pos, you get a point
        # on the circumference of the circle.
        self.front = Vector2(0, -self.radius)  # Pointing upward.
        # Just rotate the front vector by -90 and 90 degrees to get
        # the left and right vectors. `rotate` returns a new vector.
        self.left = self.front.rotate(-90)
        self.right = self.front.rotate(90)

    def update(self):
        # Use the front vector as the velocity.
        self.pos += self.front.normalize() * self.speed
        self.rect.center = self.pos

        if self.angular_speed != 0:
            self.rotate()

    def rotate(self):
        """Rotate the front vector and use it to update the other two."""
        self.front.rotate_ip(self.angular_speed)
        self.left = self.front.rotate(-90)
        self.right = self.front.rotate(90)

    def draw_vectors(self, screen):
        """Draw the three vectors."""
        pg.draw.circle(screen, (0, 240, 50), list(map(int, self.pos+self.front)), 3)
        pg.draw.circle(screen, (240, 0, 50), list(map(int, self.pos+self.left)), 3)
        pg.draw.circle(screen, (240, 240, 0), list(map(int, self.pos+self.right)), 3)
        pg.draw.line(screen, (0, 240, 50), self.pos, self.pos+self.front, 2)
        pg.draw.line(screen, (240, 0, 50), self.pos, self.pos+self.left, 2)
        pg.draw.line(screen, (240, 240, 0), self.pos, self.pos+self.right, 2)


def main():
    screen = pg.display.set_mode((640, 480))
    clock = pg.time.Clock()
    all_sprites = pg.sprite.Group()
    agent = Agent((100, 300), all_sprites)

    done = False

    while not done:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                done = True
            elif event.type == pg.KEYDOWN:
                if event.key == pg.K_w:
                    agent.speed = 5
                elif event.key == pg.K_a:
                    agent.angular_speed = -10
                elif event.key == pg.K_d:
                    agent.angular_speed = 10
            elif event.type == pg.KEYUP:
                if event.key == pg.K_w:
                    agent.speed = 0
                elif event.key == pg.K_a:
                    agent.angular_speed = 0
                elif event.key == pg.K_d:
                    agent.angular_speed = 0

        all_sprites.update()

        screen.fill((30, 30, 30))
        all_sprites.draw(screen)
        agent.draw_vectors(screen)

        pg.display.flip()
        clock.tick(30)


if __name__ == '__main__':
    pg.init()
    main()
    pg.quit()