Trouble in pygame.

[TempoGnome]

Hi!
I've been making this game for fun and have run into a few problems, a friend recommended me to ask you guys for help.

I have three problems:

1. The player doesn't recongnize when it's not on a platform and because of this it won't fall down. I've narrowed it down to the game not checking for vertical collision all the time but I don't know how I would solve this.

2. If the player is colliding with a wall and you try to use thrusters it'll fall out of the level. I have no idea why this happens, it's probably something with the collision.

3. I'm not sure what the best way to implement a camera that follows the player would be. (Note that I'll be adding enemies later and I'd rather not have to change their coordinates based on the camera.

I apologize for so many questions in one post but I figured it would be better to ask all three in one post rather than spamming you with three different posts.

I really hope someone will be able to help me! I've attached the code below.

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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,1,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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,),
            (1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,),
            (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"""
    for i in range(len(blockTypeList)): # Go through every block...
        if blockTypeList[i] == "solid": # ...and check what kind of block it is
            if player.colliderect(blockList[i]): #Apply necessary influences from the block(e.g. a solid block prevents the player from moving into it)
                if vx > 0 and not falling:
                    player.right = blockListDisp[i].left
                    print 'Collide Right'
                if vx < 0 and not falling:
                    player.left = blockListDisp[i].right
                    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
                    print 'Collide Top'
    # 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

    # 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, blockListDisp[i].y)) #blit the wall-block graphics

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

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

[TempoGnome]

Is there really no one that can help me?

[zjtpjs4]

Hello. Right, your first problem is that colliderect only checks if two rects are overlapping. So after they collide the first time, and the top equals the bottom, they are no longer overlapping and do not collide. You have no checks to see whether or not not you did collide on that tick. So a simple fix would be too check if no collision has happened, and set falling and isGrounded appropriately. A small side effect of doing this is that you code will simply move the player and declare that it is falling, so the player will constantly move up and down. You may like this, but to prevent it, you can alter your code to check where it is in terms of its sides. If you want cool effects, like the player toppling off the edge, I recomend finding a good physics engine. Do not simply check if the players bottom is equal to the rects top, as they are equal not matter where on the x-axis the player is. The second problem is that the way the collision currently works, it is very easy for it to get confused and set the wrong side. In the case of flying up, it thinks it should set the bottom of the player to the top of the block, placing it outside. As for the third problem, I have never added a camera, though I have conemplated it. I think someone else needs to answer that question. Hope this helps, If you want I can post how I would solve these problems. Cheers.

[TempoGnome]

Hi!
Thank you so much for answering! I got the first problem fixed based on your suggestion, however I don't quite understand how I should fix the thing with the player moving up and down. I would really appreciate it if you could post how you would solve it.

[zjtpjs4]

In the last section where you check if vy < 0 you can add vy = 0. This fixes that problem.Its not perfect though, for instance if hit the side of a block whilest moving vertically, the vertical checks come into play, and you jump onto the top of the block. This also halts the player in mid-air when running up against a stack of blocks like in the walls around the level. I'm sure you could fix these little annoyances. Hey, did you make the player constantly wobbling, or did you go for a fixed look?

[TempoGnome]

I want the fixed look but couldn't quite understand how you meant I should to fix it, that's actually what I meant when I asked you how you would fix it. :)

[zjtpjs4]

Oh, Ok, well I will post that code:

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

[zjtpjs4]

Also, To fix those problems I spoke of, you need to change you current collision checks to something similar to that bottom else. I've tried not to alter the code too much, so you can read it and tell whats going on. What you have right now is a move player first check if that causes a collision later. What you need to change that too is as follows:

1. check if moving is required, whether vx or vy are non-zero
2. check if that will make a collision if so move as close as you can, using the player.directection variable, like you have been.
3. if there is no collision, just move.

So this basically rearanging the collision loop and moving code from elsewhere.

[TempoGnome]

Thank you so much for all the help! I think I'll be able to do the rest on my own from here.

[zjtpjs4]

Sweet!!! Glad I could help. Remember to mark the post as solved ^__^