Okay, I'm using python and pygame, and I'm really struggling to get a ball bouncing.
Here is my code so far:
[CODE]import pygame, sys, random, math
width = 640
height = 400
screen = pygame.display.set_mode((width,height))
clock = pygame.time.Clock()
class Ball:
def __init__(self, x, y):
self.x = x
self.y = y
self.dx = 0
self.dy = 0
self.size = 10
self.color = (random.randint(0,255),random.randint(0,255),random.randint(0,255))
self.gravity = 1
def think(self):
self.x += self.dx
self.y += self.dy
if self.y + self.size < height:
self.y += self.gravity
self.gravity += 1
if self.y + self.size >= height:
self.gravity = -(self.gravity)
def draw(self):
pygame.draw.circle(screen, self.color, (self.x, self.y), self.size)
running = True
balls = []
while running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
pygame.quit()
sys.exit()
if event.type == pygame.MOUSEBUTTONDOWN:
x,y = event.pos
balls.append(Ball(x,y))
screen.fill((255,255,255))
for i in balls:
i.think()
i.draw()
pygame.display.flip()
clock.tick(40)
[/CODE]
The code generates a ball which will fall to the ground, but when it reaches the bottom, it just stops...
Any help would be very much welcomed, thank you.
[quote][code] if self.y + self.size < height:
self.y += self.gravity
self.gravity += 1
if self.y + self.size >= height:
self.gravity = -(self.gravity)[/code][/quote]
If I'm reading this correctly,
when the ball hasn't hit the floor move the ball down grav amount and increase gravity
once the ball has hit the floor, reverse gravity
but you're not moving the ball when it hits the floor, so on the next think it's still in the floor and gravity is reversed again, and again....
Reverse velocity, not gravity. Otherwise the ball will accelerate upward and fly away into the sky, rather than move upward but eventually fall back down again.
[QUOTE=Wyzard;33336276]Reverse velocity, not gravity. Otherwise the ball will accelerate upward and fly away into the sky, rather than move upward but eventually fall back down again.[/QUOTE]
He named his variables wrong. The 'gravity' variable is actually velocity. Gravitational acceleration in his program is a constant value of 1.
The real problem is that he doesn't adjust the ball's y-coordinate upon collision, so it just gets 'stuck' in the ground.
@OP: after reversing velocity like you do, you have to set self.y to height-self.size-1.
Yeah, I managed to get it to bounce, in a sort of glitchy way, I may upload a GIF of how it looks later.
The ball bounces higher with each bounce until it eventually bounces off-screen.
There's another problem also, if I keep spawning balls they start to fall throught the botton of the screen, is this a problem with my programming or Python ?
[QUOTE=joyenusi;33345808]Yeah, I managed to get it to bounce, in a sort of glitchy way, I may upload a GIF of how it looks later.
The ball bounces higher with each bounce until it eventually bounces off-screen.
There's another problem also, if I keep spawning balls they start to fall throught the botton of the screen, is this a problem with my programming or Python ?[/QUOTE]
With the programming - I had some fun with your code and that doesn't happens to me.
[QUOTE=Ehmmett;33354036]Taking a guess here.
guessing it bounces higher and higher because you're constantly adding gravity.
also guessing it falls through because it's moving too fast.[/QUOTE]
That's how gravity works, it's a constant force.
I can't see any reason why collision detection should fail either, but he hasn't posted the latest code.
Yeah, I managed to fix it, can't find a good tool to screen cap. into GIF, but here's the latest code.
I also managed to make it vaguely realistic.
[CODE]
import pygame, sys, random, math
width = 640
height = 400
screen = pygame.display.set_mode((width,height))
clock = pygame.time.Clock()
class Ball:
def __init__(self, x, y, energy):
self.x = x
self.y = y
self.dx = energy
self.dy = 0
self.size = random.randint(5,20)
self.color = (random.randint(0,255),random.randint(0,255),random.randint(0,255))
self.pos = [x,y]
self.gravity = 1
def think(self):
self.x += self.dx
self.y += self.dy
if self.x + self.size >= width:
self.dx = -(self.dx)
self.dx += 1
if self.x <= 0:
self.dx = -(self.dx)
self.dx -=1
if self.y <= 0:
self.gravity = -(self.gravity)
if self.y + self.size < height:
self.y += self.gravity
if self.gravity >= 0:
self.gravity += 1
if self.gravity < 0:
self.gravity += 1
if self.y + self.size >= height:
self.y -= (self.y-height) +(self.size+1)
self.gravity -= 10
self.gravity = -(self.gravity)
if self.dx>0:
self.dx-=1
if self.dx<0:
self.dx+=1
def draw(self):
pygame.draw.circle(screen, self.color, (self.x, self.y), self.size)
running = True
balls = []
energy = 0
mousedown = False
while running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
pygame.quit()
sys.exit()
if event.type == pygame.MOUSEBUTTONDOWN:
mousedown = True
x,y = event.pos
if event.type == pygame.MOUSEBUTTONUP:
balls.append(Ball(x,y, energy))
mousedown = False
if mousedown == True:
energy += 1
if mousedown == False:
energy = 0
## Attempt at gravity
## if len(balls) == 2:
## direction = [balls[0].x - balls[1].x, balls[0].y - balls [1].y]
## balls[0].x += direction[0] * 0.5
## balls[0].y += direction[1] * 0.5
screen.fill((255,255,255))
pygame.draw.rect(screen, (255,0,0), (10,height - energy *10-5, 20, energy*10))
for i in balls:
i.think()
i.draw()
## Removing the balls when they are off-screen, commented out as sometimes if the self.dx or dy values will force the ball off-screen before changing direction
## for i in balls:
## if i.x > width or i.x < 0 or i.y < 0 or i.y > height +10:
## balls.remove(i)
print(len(balls))
pygame.display.flip()
clock.tick(40)
[/CODE]
The gravity wasn't working properly because of the way I was handling the negation of the gravity:
[CODE]self.gravity = -(self.gravity)[/CODE]
I'm not sure, I fixed it though! :D
I am also trying to learn C# but it seems a bit more complicated, anyone recommend a fun way to learn C#, C++ and XNA ?
I attempted also to have gravitation between the balls but that's another story.
Have a play around with the code and tell me what you think.
You've went backwards, the way you have it written right now doesn't make sense.
dx and dy seem to be velocity, however you're still adding 'gravity' directly to the y-coordinate. You shouldn't do this. Gravity is a [i]constant acceleration[/i], and acceleration is the [i]second[/i] derivative of position.
Replace "self.y += self.gravity" with "self.[b]d[/b]y += self.gravity" and replace "self.gravity = -(self.gravity)" with "self.dy = -self.dy" everywhere it occurs. Don't modify gravity anywhere.
