python - 如何在pygame中平滑移动

Question

我和我的一个 friend 刚刚开始学习在 repl.it 上使用 pygame 进行编程，对于我们的第一个“真实”项目，我们想制作一个像点击冒险这样的老派游戏。

但是，我们在角色移动方面遇到了问题，如果我们单击屏幕上的某处，角色只是“传送”到那里，但我们希望它看起来尽可能平滑。

所以基本上，我们想要摆脱角色的“瞬移”，而是从角色当前位置到鼠标位置进行平滑的逐帧过渡。

我们已经尝试减慢 while 循环，以便我们可以在每次执行 while 循环时投影角色，但这只会导致整个站点崩溃，我们还尝试在 repl.it 之外进行，以防万一是网站的问题，但它在那里也不起作用。

#PMC = Character
#mpos = the mouse position 
#mstate= the state of the mouse buttons (0 if nothing is pressed, 1 if a mouse 
#button is pressed) 
#charspeed = the speed at which the character moves (=1px)
  ```
#---PMC movement when mouse click-----------------------
    #---x,y = mpos   x2,y2 = characterpos
    if mstate == (1,0,0):
      #print('x: ', x, ' y: ', y, '   x2: ', x2, ' y2: ', y2) #debugging_positions

      
      while x2 != x:
        if x2>x:
          x2-=charspeed
          screen.blit(pmc, (x2-46, y2-184))
        if x2<x:
          x2+=charspeed
          screen.blit(pmc, (x2-46, y2-184))
          
      while y2 != y:
        if y2>y:
          y2 -= charspeed
          screen.blit(pmc, (x2-46, y2-184))
        if y2<y:
          y2 += charspeed
          screen.blit(pmc, (x2-46, y2-184))

Answer 1

你有一个游戏循环，所以使用它。只需在每一帧中将角色移动到特定位置即可。例如，每帧按 step 移动角色:

step = 1

if x2 + step <= x:
    x2 += step
elif x2 - step >= x:
    x2 -= step
else:
    x2 = x

if y2 + step <= y:
    y2 += step
elif y2 - step >= y:
    y2 -= step
else:
    y2 = y

---

对于更复杂的解决方案，您必须计算 Euclidean distance形成指向目标的点。使用 pygame.math.Vector2用于计算。

计算follower和sprite之间的距离和单位方向向量从(follower_x, follower_y)到(mainsprite_x, mainsprite_y)。 Unit Vector可以通过将方向向量除以距离或通过归一化 (normalize()) 方向向量来计算:

target_vector = Vector2(mainsprite_x, mainsprite_y)
follower_vector = Vector2(follower_x, follower_y)

distance = follower_vector.distance_to(target_vector)
direction_vector = target_vector - follower_vector
if distance > 0:
    direction_vector /= distance

现在你可以定义一个精确的step_distance并移动到 Sprite 的follower int方向:

if distance > 0:
    new_follower_vector = follower_vector + direction_vector * step_distance.

定义一个maximum_distance 和一个minimum_distance。最小步距为:

min_step = max(0, distance - maximum_distance)

最大步距为

max_step = distance - minimum_distance

放在一起:

minimum_distance    = 0
maximum_distance    = 10000
target_vector       = Vector2(mainsprite_x, mainsprite_y)
follower_vector     = Vector2(follower_x, follower_y)
new_follower_vector = Vector2(follower_x, follower_y)

distance = follower_vector.distance_to(target_vector)
if distance > minimum_distance:
    direction_vector    = (target_vector - follower_vector) / distance
    min_step            = max(0, distance - maximum_distance)
    max_step            = distance - minimum_distance
    step_distance       = min_step + (max_step - min_step) * LERP_FACTOR
    new_follower_vector = follower_vector + direction_vector * step_distance

---

最小示例: repl.it/@Rabbid76/PyGame-FollowMouseSmoothly

import pygame

LERP_FACTOR      = 0.05
minimum_distance = 25
maximum_distance = 100

def FollowMe(pops, fpos):
    target_vector       = pygame.math.Vector2(*pops)
    follower_vector     = pygame.math.Vector2(*fpos)
    new_follower_vector = pygame.math.Vector2(*fpos)

    distance = follower_vector.distance_to(target_vector)
    if distance > minimum_distance:
        direction_vector    = (target_vector - follower_vector) / distance
        min_step            = max(0, distance - maximum_distance)
        max_step            = distance - minimum_distance
        step_distance       = min_step + (max_step - min_step) * LERP_FACTOR
        new_follower_vector = follower_vector + direction_vector * step_distance

    return (new_follower_vector.x, new_follower_vector.y) 

pygame.init()
window = pygame.display.set_mode((500, 500))
clock = pygame.time.Clock()

follower = (100, 100)
run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    player   = pygame.mouse.get_pos()
    follower = FollowMe(player, follower)

    window.fill(0)  
    pygame.draw.circle(window, (0, 0, 255), player, 10)
    pygame.draw.circle(window, (255, 0, 0), (round(follower[0]), round(follower[1])), 10)
    pygame.display.flip()