Pygame 中蒙版和发射光束的重叠 [AI 汽车模型视觉]

Question

我尝试在 Pygame 中使用预定义的轨道掩码实现光束碰撞检测。我的最终目标是让 AI 汽车模型能够看到它所行驶的轨道：

这是我当前的代码，我发射光束来掩盖并尝试找到重叠：

import math
import sys

import pygame as pg

RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)

pg.init()
beam_surface = pg.Surface((500, 500), pg.SRCALPHA)


def draw_beam(surface, angle, pos):
    # compute beam final point
    x_dest = 250 + 500 * math.cos(math.radians(angle))
    y_dest = 250 + 500 * math.sin(math.radians(angle))

    beam_surface.fill((0, 0, 0, 0))

    # draw a single beam to the beam surface based on computed final point
    pg.draw.line(beam_surface, BLUE, (250, 250), (x_dest, y_dest))
    beam_mask = pg.mask.from_surface(beam_surface)

    # find overlap between "global mask" and current beam mask
    hit = mask.overlap(beam_mask, (pos[0] - 250, pos[1] - 250))
    if hit is not None:
        pg.draw.line(surface, BLUE, mouse_pos, hit)
        pg.draw.circle(surface, GREEN, hit, 3)


surface = pg.display.set_mode((500, 500))
mask_surface = pg.image.load("../assets/mask.png")
mask = pg.mask.from_surface(mask_surface)
clock = pg.time.Clock()

while True:
    for e in pg.event.get():
        if e.type == pg.QUIT:
            pg.quit()
            sys.exit()

    mouse_pos = pg.mouse.get_pos()

    surface.fill((0, 0, 0))
    surface.blit(mask_surface, mask_surface.get_rect())

    for angle in range(0, 120, 30):
        draw_beam(surface, angle, mouse_pos)

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

让我们描述一下代码片段中发生的事情。一个接一个地，我绘制光束beam_surface，用它们制作蒙版，并找到与由一个矩形和一个圆形（gif 中的黑色）定义的背景蒙版重叠的部分。如果有一个“命中点”（两个面具之间的重叠点），我会用一条连接命中点和鼠标位置的线来绘制它。

它适用于角度<0,90>：

但它不适用于范围内的角度<90,360>：

Pygame 的overlap()文档说明了这一点：

从左上角开始，它检查第一行的位 0 到 W - 1 ((0, 0) 到 (W - 1, 0)) 然后继续到下一行 ((0, 1) 到 (W - 1 , 1))。检查完整个列块后，它会继续下一个（W 到 2 * W - 1）。

这意味着只有当光束大约从左上角击中掩模时，这种方法才会起作用。您对如何使其适用于所有情况有什么建议吗？这通常是解决这个问题的好方法吗？

Answer 1

如果光线轴的 x 和 y 分量指向正方向，则您的方法工作正常，但如果指向负方向，则方法失败。正如您所指出的，这是由pygame.mask.Mask.overlap 的工作方式引起的：

从左上角开始，它检查第一行的位 0 到 W - 1 ((0, 0) 到 (W - 1, 0)) 然后继续到下一行 ((0, 1) 到 (W - 1 , 1))。检查完整个列块后，它会继续下一个（W 到 2 * W - 1）。

要使算法起作用，您必须确保光线始终指向正方向。因此，如果光线指向负 x 方向，则垂直翻转遮罩和光线，如果光线指向负 y 方向而不是水平翻转光线。

使用pygame.transform.flip()顶部创建 4 个蒙版。不翻转、水平翻转、垂直翻转和垂直和水平翻转：

mask = pg.mask.from_surface(mask_surface)
mask_fx = pg.mask.from_surface(pg.transform.flip(mask_surface, True, False))
mask_fy = pg.mask.from_surface(pg.transform.flip(mask_surface, False, True))
mask_fx_fy = pg.mask.from_surface(pg.transform.flip(mask_surface, True, True))
flipped_masks = [[mask, mask_fy], [mask_fx, mask_fx_fy]]

确定射线的方向：

c = math.cos(math.radians(angle))
s = math.sin(math.radians(angle))

获取依赖于光线方向的翻转蒙版：

flip_x = c < 0
flip_y = s < 0
filpped_mask = flipped_masks[flip_x][flip_y]

计算翻转的目标点：

x_dest = 250 + 500 * abs(c)
y_dest = 250 + 500 * abs(s)

计算翻转的偏移量：

offset_x = 250 - pos[0] if flip_x else pos[0] - 250
offset_y = 250 - pos[1] if flip_y else pos[1] - 250

获取最近翻转的光线和遮罩的交点并取消翻转交点：

hit = filpped_mask.overlap(beam_mask, (offset_x, offset_y))
if hit is not None and (hit[0] != pos[0] or hit[1] != pos[1]):
    hx = 500 - hit[0] if flip_x else hit[0]
    hy = 500 - hit[1] if flip_y else hit[1]
    hit_pos = (hx, hy)

    pg.draw.line(surface, BLUE, mouse_pos, hit_pos)
    pg.draw.circle(surface, GREEN, hit_pos, 3)

看例子： repl.it/@Rabbid76/PyGame-PyGame-SurfaceLineMaskIntersect-2

import math
import sys
import pygame as pg

RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)

pg.init()
beam_surface = pg.Surface((500, 500), pg.SRCALPHA)


def draw_beam(surface, angle, pos):
    c = math.cos(math.radians(angle))
    s = math.sin(math.radians(angle))

    flip_x = c < 0
    flip_y = s < 0
    filpped_mask = flipped_masks[flip_x][flip_y]
    
    # compute beam final point
    x_dest = 250 + 500 * abs(c)
    y_dest = 250 + 500 * abs(s)

    beam_surface.fill((0, 0, 0, 0))

    # draw a single beam to the beam surface based on computed final point
    pg.draw.line(beam_surface, BLUE, (250, 250), (x_dest, y_dest))
    beam_mask = pg.mask.from_surface(beam_surface)

    # find overlap between "global mask" and current beam mask
    offset_x = 250 - pos[0] if flip_x else pos[0] - 250
    offset_y = 250 - pos[1] if flip_y else pos[1] - 250
    hit = filpped_mask.overlap(beam_mask, (offset_x, offset_y))
    if hit is not None and (hit[0] != pos[0] or hit[1] != pos[1]):
        hx = 499 - hit[0] if flip_x else hit[0]
        hy = 499 - hit[1] if flip_y else hit[1]
        hit_pos = (hx, hy)

        pg.draw.line(surface, BLUE, pos, hit_pos)
        pg.draw.circle(surface, GREEN, hit_pos, 3)
        #pg.draw.circle(surface, (255, 255, 0), mouse_pos, 3)


surface = pg.display.set_mode((500, 500))
#mask_surface = pg.image.load("../assets/mask.png")
mask_surface = pg.Surface((500, 500), pg.SRCALPHA)
mask_surface.fill((255, 0, 0))
pg.draw.circle(mask_surface, (0, 0, 0, 0), (250, 250), 100)
pg.draw.rect(mask_surface, (0, 0, 0, 0), (170, 170, 160, 160))

mask = pg.mask.from_surface(mask_surface)
mask_fx = pg.mask.from_surface(pg.transform.flip(mask_surface, True, False))
mask_fy = pg.mask.from_surface(pg.transform.flip(mask_surface, False, True))
mask_fx_fy = pg.mask.from_surface(pg.transform.flip(mask_surface, True, True))
flipped_masks = [[mask, mask_fy], [mask_fx, mask_fx_fy]]

clock = pg.time.Clock()

while True:
    for e in pg.event.get():
        if e.type == pg.QUIT:
            pg.quit()
            sys.exit()

    mouse_pos = pg.mouse.get_pos()

    surface.fill((0, 0, 0))
    surface.blit(mask_surface, mask_surface.get_rect())

    for angle in range(0, 359, 30):
        draw_beam(surface, angle, mouse_pos)

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

不是，算法可以进一步改进。光线总是绘制在 的右下象限上beam_surface。因此不再需要其他 3 个象限，大小beam_surface可以减少到 250x250。射线的起点在 (0, 0) 而不是 (250, 250) 并且偏移的计算必须稍微调整：

beam_surface = pg.Surface((250, 250), pg.SRCALPHA)

def draw_beam(surface, angle, pos):
    c = math.cos(math.radians(angle))
    s = math.sin(math.radians(angle))

    flip_x = c < 0
    flip_y = s < 0
    filpped_mask = flipped_masks[flip_x][flip_y]
    
    # compute beam final point
    x_dest = 500 * abs(c)
    y_dest = 500 * abs(s)

    beam_surface.fill((0, 0, 0, 0))

    # draw a single beam to the beam surface based on computed final point
    pg.draw.line(beam_surface, BLUE, (0, 0), (x_dest, y_dest))
    beam_mask = pg.mask.from_surface(beam_surface)

    # find overlap between "global mask" and current beam mask
    offset_x = 499-pos[0] if flip_x else pos[0]
    offset_y = 499-pos[1] if flip_y else pos[1]
    hit = filpped_mask.overlap(beam_mask, (offset_x, offset_y))
    if hit is not None and (hit[0] != pos[0] or hit[1] != pos[1]):
        hx = 499 - hit[0] if flip_x else hit[0]
        hy = 499 - hit[1] if flip_y else hit[1]
        hit_pos = (hx, hy)

        pg.draw.line(surface, BLUE, pos, hit_pos)
        pg.draw.circle(surface, GREEN, hit_pos, 3)