Pygame 在旧文本上呈现文本

Question

我有以下函数可以绘制到 pygame window:

    base.draw(win, rocket.in_space)
win.blit(rocket_img, (120, 150))
if rocket.in_space:
    velocity_label = STAT_FONT.render(f"Velocity: {round(rocket.velocity, 3)} km/s", True, (255, 255, 255))
    acceleration_label = STAT_FONT.render(f"Acceleration: {round(rocket.acceleration, 3)} km/s^2", True, (255, 255, 255))
    altitude_label = STAT_FONT.render(f"Altitude: {round(rocket.altitude, 3)} km", True, (255, 255, 255))
    fuel_label = STAT_FONT.render(f"Fuel: {round(rocket.fuel, 2)} kg", True, (255, 255, 255))
    time_label = STAT_FONT.render(f"Time: {round(rocket.time_passed, 2)} s", True, (255, 255, 255))
else:
    velocity_label = STAT_FONT.render(f"Velocity: {round(rocket.velocity, 3)} km/s", True, (0, 0, 0))
    acceleration_label = STAT_FONT.render(f"Acceleration: {round(rocket.acceleration, 3)} km/s^2", True, (0, 0, 0))
    altitude_label = STAT_FONT.render(f"Altitude: {round(rocket.altitude, 3)} km", True, (0, 0, 0))
    fuel_label = STAT_FONT.render(f"Fuel: {round(rocket.fuel, 2)} kg", True, (0, 0, 0))
    time_label = STAT_FONT.render(f"Time: {round(rocket.time_passed, 2)} s", True, (0, 0, 0))
win.blit(velocity_label, (0, 0))
win.blit(acceleration_label, (0, 50))
win.blit(altitude_label, (0, 100))
win.blit(fuel_label, (0, 150))
win.blit(time_label, (0, 200))
pygame.display.update()

以及使背景移动的代码：

class Base:
VEL = 5
HEIGHT = bg_img.get_height()
IMG = bg_img
space = space_img

def __init__(self, x):
    self.x = x
    self.y1 = 0
    self.y2 = self.HEIGHT

def move(self, vel):
    self.VEL = vel
    self.y1 -= self.VEL
    self.y2 -= self.VEL
    if self.y1 + self.HEIGHT < 0:
        self.y1 = self.y2 + self.HEIGHT

    if self.y2 + self.HEIGHT < 0:
        self.y2 = self.y1 + self.HEIGHT

def draw(self, win, in_space):
    if in_space:
        win.blit(self.space, (self.x, self.y2))
        win.blit(self.space, (self.x, self.y1))
    else:
        win.blit(self.IMG, (self.x, self.y2))
        win.blit(self.IMG, (self.x, self.y1))

但是，当背景开始加速时，文本开始在自身上渲染。我不确定为什么会这样。非常感谢任何帮助。

编辑： 基地移动的速度随时间增加

这是屏幕冻结时的样子。

Answer 1

问题是计算背景的y坐标。如果 self.VEL 大于 HEIGHT，则算法失效。使用取模 (%) 运算符计算 y 坐标：

class Base:
    VEL = 5
    HEIGHT = bg_img.get_height()
    IMG = bg_img
    space = space_img

    def __init__(self, x):
        self.x = x
        self.y = 0

    def move(self, vel):
        self.VEL = vel
        self.y = (self.y - self.VEL) % self.HEIGHT
        
    def draw(self, win, in_space):
    if in_space:
        win.blit(self.space, (self.x, self.y - self.HEIGHT))
        win.blit(self.space, (self.x, self.y))
    else:
        win.blit(self.IMG, (self.x, self.y - self.HEIGHT))
        win.blit(self.IMG, (self.x, self.y))

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