Scrolling camera

Question

I've been tinkering with a scrolling camera that follows the player around and have got it to follow the player. The problem is that it moves slower than the player and because of this the player wont stay in the middle of the screen.

I believe the problem is in the offset (cameraX) and have tried a few different values but haven't found any that work.

Code:

import pygame, sys, time, random, math
from pygame.locals import *

BACKGROUNDCOLOR = (255, 255, 255)

WINDOWW = 800 
WINDOWH = 600
PLAYERW = 66
PLAYERH = 22
FPS = 60
MOVESPEED = 3
YACCEL = 0.13
GRAVITY = 2
BLOCKSIZE = 30

pygame.init()
screen = pygame.display.set_mode((WINDOWW, WINDOWH), 0, 32)
mainClock = pygame.time.Clock()

testLevel = [
            (1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,),
            (1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,)]

def createblock(length, height, color):
    tmpblock = pygame.Surface((length, height))
    tmpblock.fill(color)
    tmpblock.convert()
    return tmpblock

def terminate(): # Used to shut down the software
    pygame.quit()
    sys.exit()

def add_level(lvl, bSize): # Creates the level based on a map (lvl) and the size of blocks
    bList = [] # List of every block
    bListDisp = [] # List of every block to display    
    bTypeList = [] # List with corresponding type of block(wall, air, etc.)

    for y in range(len(lvl)): 
        for x in range(len(lvl[0])):

            if lvl[y][x] == 0: # If the block type on lvl[y][x] is '0', write "air" down in the type list
                bTypeList.append("air")
            elif lvl[y][x] == 1: # If the block type on lvl[y][x] is '1', write "wall" down in the type list
                bTypeList.append("solid")

            bList.append(pygame.Rect((bSize * x), (bSize * y), bSize, bSize)) #Append every block that is registered
            bListDisp.append(pygame.Rect((bSize * x), (bSize * y), bSize, bSize)) #Append every block to display that is registered

    return bList, bListDisp, bTypeList

player = pygame.Rect((WINDOWW/2), (WINDOWH - BLOCKSIZE*3), PLAYERW, PLAYERH)
wallblock = createblock(BLOCKSIZE, BLOCKSIZE,(20,0,50))

lastTime = pygame.time.get_ticks()
isGrounded = False

vx = 0
vy = 0

allLevels = [testLevel] # A list containing all lvls(only one for now)
maxLevel = len(allLevels) # Checks which level is the last
currLevel = allLevels[0] # Current level(start with the first lvl)
blockList, blockListDisp, blockTypeList = add_level(currLevel, BLOCKSIZE) # A list with every block and another list with the blocks types

thrusters = True
jumping = False
falling = True
while True:
    """COLLISION"""
    collision = False
    for i in range(len(blockTypeList)):
        if blockTypeList[i] == "solid":
            if player.colliderect(blockList[i]): 
                collision = True
                if vx > 0 and not falling:
                    player.right = blockListDisp[i].left
                    vx = 0
                    print('Collide Right')
                if vx < 0 and not falling:
                    player.left = blockListDisp[i].right
                    vx = 0
                    print('Collide Left')
                if vy > 0:
                    player.bottom = blockListDisp[i].top
                    isGrounded = True
                    falling = False
                    vy = 0
                    print('Collide Bottom')
                if vy < 0:
                    player.top = blockListDisp[i].bottom
                    vy = 0
                    print('Collide Top')
            else:
                player.bottom += 1
                if player.colliderect(blockList[i]):
                    collision = True
                    #isGrounded = True
                    #falling = False
                player.bottom -= 1
    if not collision:
        falling = True
        isGrounded = False

    # Input
    pressedKeys = pygame.key.get_pressed() # Checks which keys are being pressed
    timeDiff = pygame.time.get_ticks() - lastTime # Calculates time difference 
    lastTime +=  timeDiff # Last time checked reset to current time

    # Shut-down if the ESC-key is pressed or the window is "crossed down"
    for event in pygame.event.get():
        if event.type == QUIT or event.type == KEYDOWN and event.key == K_ESCAPE:
            terminate()    

    """X-axis control"""
    if pressedKeys[ord('a')]:
        vx = -MOVESPEED
    if pressedKeys[ord('d')]:
        vx = MOVESPEED
    if not pressedKeys[ord('d')] and not pressedKeys[ord('a')]:
        vx = 0

    """Y-axis control"""
    # Controls for jumping
    if pressedKeys[ord('w')] and thrusters == True:
            vy -= YACCEL * timeDiff; # Accelerate along the y-xis when "jumping", but not above/below max speed
            if vy <= -4:
                vy = -4
            isGrounded = False # You are airborne
            jumping = True # You are jumping

    if event.type == KEYUP: # If you let go of the "jump"-button, stop jumping
        if event.key == ord('w') and vy < 0 and not isGrounded:
            jumping = False
            falling = True

    player.x += vx
    player.y += vy
    cameraX = player.x - WINDOWW/2

    # Gravity
    if not isGrounded or falling:
        vy += 0.3
        if vy > 80:
            vy = 80

    screen.fill(BACKGROUNDCOLOR)

    for i in range(len(blockTypeList)):
        if blockTypeList[i] == "solid":
            screen.blit(wallblock, (blockListDisp[i].x-cameraX, blockListDisp[i].y)) #blit the wall-block graphics

    pygame.draw.rect(screen, (0, 0, 0), player)

    pygame.display.update()
    mainClock.tick(FPS)

related: [How to add scrolling to a platformer in pygame?](http://stackoverflow.com/questions/14354171/how-to-add-scrolling-to-a-platformer-in-pygame) — sloth, Apr 25 '13 at 10:02

sloth · Accepted Answer · 2013-04-25T10:01:58.757

You don't apply the camera-offset to the player itself, only to the wallblocks.

So change

pygame.draw.rect(screen, (0, 0, 0), player)

to

pygame.draw.rect(screen, (0, 0, 0), player.move(-cameraX, 0))

Some more notes:

Using three lists (blockList, blockListDisp, blockTypeList) to keep track of your level is way to complex, use a single list :-)

Change your add_level to:

# use a dict to keep track of possible level blocks, so adding new ones becomes simple
types = {0: "air", 1: "solid"}

def add_level(lvl, bSize): # Creates the level based on a map (lvl) and the size of blocks
    for y in range(len(lvl)): 
        for x in range(len(lvl[0])):
            # no more if/elif
            yield types[lvl[y][x]], pygame.Rect((bSize * x), (bSize * y), bSize, bSize)

your lists to:

blocks = list(add_level(currLevel, BLOCKSIZE)) # a single list which holds the type and rect for each block of the level

Then your collision detection can look like this:

while True:
    """COLLISION"""
    collision = False
    for type, rect in blocks: # list contains a tuple of type, rect
        if type == "solid":
            if player.colliderect(rect): 
                collision = True
                if vx > 0 and not falling:
                    player.right = rect.left # now you can always use the rect directly instead of accesing other lists
                    vx = 0
                    print('Collide Right')
 ...

Also, the drawing code becomes simpler:

for type, rect in blocks:
    if type == "solid":
        screen.blit(wallblock, rect.move(-cameraX, 0)) #blit the wall-block graphics

pygame.draw.rect(screen, (0, 0, 0), player.move(-cameraX, 0))

In the long run, you may want to use a class instead of a tuple, but that's another topic.

I added some more notes to improve your code a little bit of you don't mind :-) — sloth, Apr 25 '13 at 10:02

Scrolling camera

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