How would I make a scrolling camera in Pygame?

Question

I am asking the question I did because I need a scrolling camera. I already tried a few methods on a camera, but none of them worked. Or they said that there was a global name error. This is the code I used that has a globalname error

import pygame

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)


screen_width = 700
screen_height = 400

half_width = int(screen_width / 2)
half_height = int(screen_height / 2)


def main():
    screen = pygame.display.set_mode([screen_width, screen_height])

    pygame.display.set_caption("RPG")
    global cameraX, cameraY



    pygame.init()

    player = pygame.image.load("Textures(Final)\Whoo_For_Testing.bmp").convert()
    playerect = player.get_rect()
    player.set_colorkey(WHITE)


    grasstile = pygame.image.load("Textures(Final)\Grass_Tile.bmp").convert()
    watertile = pygame.image.load("Textures(Final)\Water_Tile.bmp").convert()
    waterbeach = pygame.image.load("Textures(Final)\Water_Beach.bmp").convert()
    grassrect = grasstile.get_rect()
    waterrect = watertile.get_rect()
    waterb = waterbeach.get_rect()

    TILE_WIDTH = 32
    TILE_HEIGHT = 32

    tilemap = [
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile]
            ]

    total_level_width = len(tilemap[0]) * 32
    total_level_height = len(tilemap)*32

    camera = Camera(simple_camera ,total_level_width, total_level_height)


    map_surface = pygame.Surface(( len(tilemap[0])*TILE_WIDTH, len(tilemap)*TILE_HEIGHT))

    for y,row in enumerate(tilemap):
        for x,tile_surface in enumerate(row):
            map_surface.blit(tile_surface,(x*TILE_WIDTH,y*TILE_HEIGHT))

    map_surface = pygame.transform.scale(map_surface, (1200, 800))
    player = pygame.transform.scale(player, (50, 100))


    done = False

    clock = pygame.time.Clock()

    move_speed = 5
    x, y = 100, 100

    entities = pygame.sprite.Group()

    while not done:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                done = True

        keys = pygame.key.get_pressed()
        if keys[pygame.K_UP]:
            y -= move_speed
        elif keys[pygame.K_DOWN]:
            y += move_speed
        elif keys[pygame.K_LEFT]:
            x -= move_speed
        elif keys[pygame.K_RIGHT]:
            x += move_speed

        screen.fill(BLACK)

        screen.blit(map_surface, grassrect)
        screen.blit(player, (x,y))


        camera.update(player)

        clock.tick(20)

        pygame.display.flip()

class Camera(object):
    def __init__(self, camera_func, width, height):
        self.camera_func = camera_func
        self.state = Rect(0, 0, width, height)

    def apply(self, target):
        return target.rect.move(self.state.topleft)

    def update(self, target):
        self.state = self.camera_func(self.state, target.rect)


def simple_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera
    return Rect(-l+HALF_WIDTH, -t+HALF_HEIGHT, w, h)

def complex_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera
    l, t, _, _ = -l+HALF_WIDTH, -t+HALF_HEIGHT, w, h

    l = min(0, l)                           # stop scrolling at the left edge
    l = max(-(camera.width-WIN_WIDTH), l)   # stop scrolling at the right edge
    t = max(-(camera.height-WIN_HEIGHT), t) # stop scrolling at the bottom
    t = min(0, t)                           # stop scrolling at the top
    return Rect(l, t, w, h)

if __name__ == "__main__":
    main()



pygame.quit()

So essentially what I am asking is how to fix this. Sorry, not that good at explaining stuff. Thank you!

This specific question relates to scrolling and the explanation of the camera is very good http://stackoverflow.com/questions/14354171/add-scrolling-to-a-platformer-in-pygame — Harvey, Apr 20 '14 at 09:21

score 0 · Accepted Answer · answered Apr 20 '14 at 20:39

There are a couple things to fix here. Firstly about the NameErrors, those were occurring because since Rect is from the imported pygame package, you have to either import Rect specifically: from pygame import Rect or write pygame.Rect. (Also watch out for capitals in your global variables!). Now, as for the actual camera problems, the main problem you had was that the player's rect which you pass to your camera function is not a moved rect, it is just the rect pygame uses to store the surface's size (so is topleft will always be (0,0)). You were also not applying your camera to the rects of the surfaces when you actually drew them. Here is the code I got to work:

import pygame

BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)


SCREEN_WIDTH = 700
SCREEN_HEIGHT = 400

HALF_WIDTH = int(SCREEN_WIDTH / 2)
HALF_HEIGHT = int(SCREEN_HEIGHT / 2)


def main():
    screen = pygame.display.set_mode([SCREEN_WIDTH, SCREEN_HEIGHT])

    pygame.display.set_caption("RPG")
    global cameraX, cameraY



    pygame.init()

    #player = pygame.image.load("Textures(Final)\Whoo_For_Testing.bmp").convert()
    player = pygame.Surface((40,40))
    player.fill((255,0,0))

    playerrect = player.get_rect()
    player.set_colorkey(WHITE)


    #grasstile = pygame.image.load("Textures(Final)\Grass_Tile.bmp").convert()
    #watertile = pygame.image.load("Textures(Final)\Water_Tile.bmp").convert()
    #waterbeach = pygame.image.load("Textures(Final)\Water_Beach.bmp").convert()
    grasstile = pygame.Surface((40,40))
    watertile = pygame.Surface((40,40))
    waterbeach = pygame.Surface((40,40))
    grasstile.fill((0,200,0))
    watertile.fill((0,0,200))
    waterbeach.fill((200,200,250))

    grassrect = grasstile.get_rect()
    waterrect = watertile.get_rect()
    waterb = waterbeach.get_rect()

    TILE_WIDTH = 32
    TILE_HEIGHT = 32

    tilemap = [
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile],
                [grasstile, grasstile, grasstile, grasstile, waterbeach, watertile, watertile, watertile, watertile]
            ]

    total_level_width = len(tilemap[0]) * 32
    total_level_height = len(tilemap)*32

    camera = Camera(simple_camera ,total_level_width, total_level_height)


    map_surface = pygame.Surface(( len(tilemap[0])*TILE_WIDTH, len(tilemap)*TILE_HEIGHT))

    for y,row in enumerate(tilemap):
        for x,tile_surface in enumerate(row):
            map_surface.blit(tile_surface,(x*TILE_WIDTH,y*TILE_HEIGHT))

    map_surface = pygame.transform.scale(map_surface, (1200, 800))
    player = pygame.transform.scale(player, (50, 100))


    done = False

    clock = pygame.time.Clock()

    move_speed = 5
    x, y = 100, 100

    entities = pygame.sprite.Group()

    while not done:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                done = True

        keys = pygame.key.get_pressed()
        if keys[pygame.K_UP]:
            y -= move_speed
        elif keys[pygame.K_DOWN]:
            y += move_speed
        elif keys[pygame.K_LEFT]:
            x -= move_speed
        elif keys[pygame.K_RIGHT]:
            x += move_speed

        screen.fill(BLACK)

        screen.blit(map_surface, camera.apply(grassrect))
        screen.blit(player, camera.apply(pygame.Rect(x,y,50,100)))

        camera.update(player.get_rect().move((x,y)))

        clock.tick(20)

        pygame.display.flip()

class Camera(object):
    def __init__(self, camera_func, width, height):
        self.camera_func = camera_func
        self.state = pygame.Rect(0, 0, width, height)

    def apply(self, rect):
        return rect.move(self.state.topleft)

    def update(self, target_rect):
        self.state = self.camera_func(self.state, target_rect)

def simple_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera

    return pygame.Rect(-l+HALF_WIDTH, -t+HALF_HEIGHT, w, h)

def complex_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera
    l, t, _, _ = -l+HALF_WIDTH, -t+HALF_HEIGHT, w, h

    l = min(0, l)                           # stop scrolling at the left edge
    l = max(-(camera.width-SCREEN_WIDTH), l)   # stop scrolling at the right edge
    t = max(-(camera.height-SCREEN_HEIGHT), t) # stop scrolling at the bottom
    t = min(0, t)                           # stop scrolling at the top
    return pygame.Rect(l, t, w, h)

if __name__ == "__main__":
    main()



pygame.quit()

This works with your simple_camera method, but not the complex_camera method, which I will leave to you to try and fix.

Thank you, I will now attempt to fix the complex_camera method with your help you gave in the first paragraph. Thank you, again. — TCVM, Apr 21 '14 at 04:02

How would I make a scrolling camera in Pygame?

1 Answers1