I'm writing a simple game with PyGame, and I've run into a problem getting things moving properly. I'm not experienced with game programming, so I'm not sure if my approach is even correct..
I have a class Ball, which extends PyGame's Sprite class. Each frame, the Ball object is supposed to move around the screen. I'm using frame-independent(?)/time-based movement with the time delta returned by PyGame's Clock object each time around. Such as,
class Ball(pygame.sprite.Sprite):
# . . .
def update(self, delta):
self.rect.x += delta * self.speed # speed is pixels per second
self.rect.y += delta * self.speed # ... or supposed to be, anyway
... and ...
class Game(object):
# . . .
def play(self):
self.clock = pygame.time.Clock()
while not self.done:
delta = self.clock.tick(self.fps) / 1000.0 # time is seconds
self.ball.update(delta)
PyGame's Sprite class is backed by a Rect object (rect) that tracks the sprite's position. And Rect's coordinates are automatically converted to integers whenever a value is updated. So, my problem is that each time update() is called, any extra fraction-of-a-pixel movement is lost, instead of being accumulated over time as it should. Speed in "pixels per second" isn't accurate this way. Even worse, if the amount of movement per frame is less than one pixel, the ball doesn't move at all for those frames, because it's always rounded down to zero. (i.e., no movement if pps < fps)
I'm not sure how to deal with this. I tried adding separate x and y values to Ball which aren't forced to be integers and updating the rect every time those change. That way the x and y values accumulate the fractions of a pixel as normal. As in,
class Ball(pygame.sprite.Sprite):
# . . .
def update(self, delta):
self.x += delta * self.speed
self.y += delta * self.speed
def getx(self):
return self._x
def setx(self, val):
self._x = val # this can be a float
self.rect.x = val # this is converted to int
def gety(self):
return self._y
def sety(self, val):
self._y = val # this can be a float
self.rect.y = val # this is converted to int
x = property(getx,setx)
y = property(gety,sety)
But that ends up being messy: it's easy to update the rect object when x and y change, but not the other way around. Not to mention the Rect object has lots of other useful coordinates that can be manipulated (like centerx, top, bottomleft, etc. -- which is why one would still want to move the rect directly). I'd more or less end up having to re-implement the whole Rect class in Ball, to store floats before it passes them down to the rect object, or else do everything based on just x and y, sacrificing some of the convenience of the Rect class either way.
Is there a smarter way to handle this?
I don't know if you still need the answer, but I figured this out a bit ago and thought I'd give this question an answer since I came across it in trying to figure out what was going on. (Thanks for helping me confirm the issue, by the way.)
You can make use of Python's round function. Pretty much, just throw what you want into that function, and it'll spit out a properly rounded number.
The first way I got it working was like this:
x = box['rect'].x
if leftDown:
x -= 300 * deltaTime
if rightDown:
x += 300 * deltaTime
box['rect'].x = round(x)
(Where my deltaTime is a float, being a fraction of a second.)
As long as you're putting the float value you get through the round function before applying it, that should do the trick. It doesn't have to use separate variables or anything.
It may be worth noting that you cannot draw in fractions of a pixel. Ever. If you're familiar with a Lite-Brite, pixels work in that way, being a single lit up light. That's why the number you use in the end has to be an integer.
Related
I am building a physical simulation and would like to make a pygame visualization.
For position and velocity calculations I use Vector2, which works very well.
It would be helpful to use the built-in rectangular collision detection. Unfortunately I have to round the current position to one pixel for the rectangle first. Since 1 pixel was set to 1 meter in my simulation, I can only determine physical collisions within 1 meter. Does anyone have an idea how I could solve this problem? My only idea would be to change the scale to 10 pixels for 1 meter to get an accuracy of 10 centimeters, but then I can only display 100m at 1000 pixels. Perhaps somebody knows a good solution for that! Thank you for your help!
If your code serves the purpose to solve a simulation you should separate the simulation from the visualization. Because now you are experiencing the fact, that you have to limit your simulation, because of visualization issues. That should not be the case.
My suggestion would be to use a combination of numpy and scipy to run your simulation without pygame (even Vector2 or Rect from pygame). If you need to detect collisions in you simulation you can implement a rectangle collision yourself very quickly:
class Rectangle(object):
def __init__(self, left, bottom, width, height):
self.left = left
self.bottom = bottom
self.width = width
self.height = height
#property
def right(self):
return self.left + self.width
#property
def top(self):
return self.bottom + self.height
def collide_with_rectangle(self, other):
if self.left > other.right or self.right < other.left or self.bottom > other.top or self.top < other.top:
return False
return True
The advantage of this approach is, that you can separate the visualization from your simulation logic. For example, if you recognize that pygame is not fitting your needs, you can switch very easy to matplotlib or any other framework.
When you separated your simulation logic you can scale your visualization easily. Because you take all points from your simulation and multiply a visualization/zoom factor.
I am trying to train a NEAT algorithm to play a simple game called 'curvefever'.
I was able to create a pygame version of curvefever and now I want to train the AI to play it.
Therefore, the AI has to learn to avoid obstacles: borders surrounding the game and tracks that each player leaves behind, like in Snake.
At the moment I am doing this in the following way:
Each player has a set of 'sensors' reaching forward that detect if and how far away an obstacle is.
Each 'sensor' is a straight line consisting of several pygame rectangles.
For each sensor it will detect if a collision with one of the obstacle rectangles occurred and calculate the distance of the collision to the player.
Which sensor detected the collision and the distance of the collision is the information that goes to the neural network.
The problem is that this is very slow! Running 'python -m cProfile -s cumtime ai.py' I figured that it is the detection of obstacles that is slowing the script down, taking up about 50% of the total runtime.
Please see some code below how I create the lines of sight:
posx = x-position of player
posy = y-position of player
dir = direction the player is going
dangle = is the degree-spacing between lines of sight
angle = total range (in degrees) of lines of sight
def create_lines_of_sight(posx, posy, dir, dangle, angle, length):
dirs = [xdir for xdir in np.ceil(np.arange(dir-angle,dir+angle,dangle))]
d_posx = np.cos(np.deg2rad(dir))
d_posy = np.sin(np.deg2rad(dir))
return list(map(functools.partial(f_lrects,posx,posy,length), dirs))
def create_rects(posx, posy, d_posx, d_posy, i):
return f_rect(posx+i*d_posx,posy+i*d_posy,1,1,0,curvefever.WHITE)
f_create_rect = create_rects
def create_line_of_rects(posx, posy, length,dir):
l = pygame.sprite.Group()
ladd = l.add
d_posx = np.cos(np.deg2rad(dir))
d_posy = np.sin(np.deg2rad(dir))
i = [i for i in range(2,length,8)]
ladd(map(functools.partial(f_create_rect,posx,posy,d_posx,d_posy),i))
return l
f_lrects = create_line_of_rects
All obstacles are rectangles defined as:
class Rect(pygame.sprite.Sprite):
def __init__(self,x,y,width,height,dir,color):
super().__init__()
self.image = pygame.Surface([width, height])
self.image.fill(color)
self.rect = self.image.get_rect()
self.rect.centerx = x
self.rect.centery = y
and are saved in a sprite group.
What I tried
I tried adding a map command to get rid of the for loop, that did not speed it up much.
I tried adding the function names to remove the function lookup, I read this makes it faster, but it didn't.
I tried detecting an obstacle using 'Bresenham's Line Algorithm' and checking if an obstacle (x,y) position overlaps with the line of sight. Although this was a faster it did not work as it often missed obstacles. This happened because the line of sight did not exactly match the obstacle centre (rectx,recty) although it did overlap with the rectangle itself.
What do other people use to detect obstacles (maybe in pygame)? Any tips on how I can make this faster or more efficient are very welcome.
Thank you very much for your help!
I've been working on a similar project.
In the end I've used the pygame.Rect.clipline() and pygame.Vector2.distance_to() methods of pygame:
def intersect_rect(self,other) -> tuple[float,float]:
cl=other.clipline(self.a.x,self.a.y,self.b.x,self.b.y)
if cl:
return cl[0] if self.a.distance_to(cl[0]) <self.a.distance_to(cl[1]) else cl[1]
else:
return
self and other are both of a class, that inherited form the pygame.Rect class. self.a and self.b are two pygame.Vector2 objects. Where self.a is in the origin of the player and self.b the LoS.
This resulted in a speedup of 100x, compared to a pure python function.
I'm practicing making an android app in pygame, and decided to do your classic bubble shooter. I have run into a problem though where the projectile launched by the player isn't accurate enough.
def move (self, time_passed):
x = (math.sin(self.angle) * self.speed) * time_passed
y = (math.cos(self.angle) * self.speed) * time_passed
c = self.rect.center
self.rect.center = (c[0]+x, c[1]+y)
def update(self, screen, time_passed):
if self.launched:
if not self.mpos:
self.mpos = pygame.mouse.get_pos()
diffx, diffy = (self.mpos[0]-self.rect.center[0],
self.mpos[1]-self.rect.center[1])
self.angle = math.atan2(diffx, diffy)
self.move(time_passed)
The screen and time_passed arguments are passed from the main loop and are the display and returned value of the Clock class's tick(60)/1000.0, for the sake of clarity.
If I print the values of x and y from move() it's very accurate: x: 1.0017224084 y: -21.9771825359, or something similar depending on where the mouse is. However, it seems pygame or move_ip only work with integers. I can click between what would be 1.00000001 and 1.9999999 and the ball will shoot in the exact spot, being 1 (in reference to the x coordinate). This is bad for my game. Is there a solution to this so I can get my objects to move very precisely?
EDIT: I realized I pasted in the wrong code. self.rect.center = (c[0]+x, c[1]+y) is where self.rect.move_ip(x, y) should be. Both methods yield the same result, however.
Keep track of your own positions using precise float values, and then instead of incrementally moving your Rects from frame to frame, just place them at their proper (integer-ized) positions each frame. That way you don't suffer from the sum of each frame's rounding error, but instead only have a single rounding involved at any given time.
I'm learning Pygame, and like most people (I think) am writing a little game to get a handle on it. That being said, feel free to answer my questions as well as critique anything else if it sucks.
So, the issue is with my "boss" object. It's supposed to drop into the game from above, and then start firing a random number of shots in a 360deg circle. It works sometimes, but I am noticing a few things going on that I didn't expect. 1) The bullets should be moving at a constant speed, but they seem to slow down over time, and move faster along the Y plane than the X. 2) Despite there being minimum 8 shots, I often only see 3-4 (pretty sure some are overlapping as I often see one shot that looks a little bigger), and some will shoot down and to the right and one will shoot in the opposite direction. It shouldn't do that. So, here's the code. I'll post the shooting calculations, and then the bullet (Fireball) instance. The rest is pretty typical from what I've seen. I update and draw by calling the sprite group they're in, which are called at the bottom of my main loop.
def shoot (self, shots, time_passed):
angle = (math.pi*2)/shots
for i in xrange(shots):
bullet = Fireball("fireball.png", self.direction, 100)
bullet.angle = angle
bullet.pos = ((math.sin(bullet.angle) * bullet.speed) * time_passed,
(math.cos(bullet.angle) * bullet.speed) * time_passed)
Fireball.container.remove(bullet)
EnemyFireball.container.add(bullet)
bullet.rect.center = self.rect.center
angle += angle
And this is the bullet:
class Fireball (pygame.sprite.Sprite):
container = pygame.sprite.Group()
def __init__ (self, image, direction, speed):
pygame.sprite.Sprite.__init__ (self, self.container)
self.image = pygame.image.load(image).convert_alpha()
self.rect = self.image.get_rect()
self.radias = ((self.rect.width/2 + self.rect.height/2)/2)
self.speed = speed
self.direction = direction
self.angle = -1
def update (self, time_passed):
if self.angle != -1:
self.rect.move_ip(self.pos)
else:
self.rect.move_ip(0, (self.speed*time_passed) * self.direction)
if self.rect.bottom < 0: self.kill()
if self.rect.top > 2000: self.kill()
If I may draw a picture... 0 <-- boss, and lines for bullets.
What I expect:
\|/
-0-
/|\
What I am seeing:
\
0-
|\
... and the bullet down straight down always looks larger, so I think there's some overlapping, but I can't see why. Time_passed is just the time calculated between Clock.tick(60), and the shots argument is a randint between 8-16.
I hope that all makes sense. If not, let me know. I'll try to clarify. Thanks in advance for the help.
Here's a link to the the source if more context is needed. Don't worry, there's not much. http://code.google.com/p/scroller-practice/source/browse/
you need to keep angle in two variables.
The right way to do it would be
curr_angle = 0
angle_step = (math.pi*2)/shots
and then at the end of each loop
curr_angle += angle_step
the way you do it, you end up with angles angle, then 2*angle, then 4*angle and so forth.
if you take away all the other parts and just have a loop that is
angle = (math.pi*2)/shots
for i in xrange(shots):
angle += angle
it should be clear that you're doubling angle each time instead of incrementing it.
I have a bunch of objects at different coordinates, and I need to animate them moving to another coordinate
ie.
one object is at coodinate (234,30) and I need it to go to (310,540).
How do I do this in pygame? I tried messing around with slope and stuff like that but I couldn't get my object,s position to smoothly go there.
Well, you should just change it's coordinates in your game loop.
There's two ways you can do this.
First, for example, if you want your object to move 50px per second, you should send your update function ticks in every frame, and then change your object's x and y coordinates by x + x_speed * ticks / 1000 (here, ticks is in miliseconds, so you should convert it to seconds).
def update_object(ticks):
object.x += float(x_speed) * ticks / 1000 # converting to float is needed
# this is your main game loop
time = pygame.time.Clock()
ticks = 0
while running:
...
update_object(ticks)
ticks = time.tick(30) # this 30 means time.tick() waits enough to make your max framerate 30
Note that you may need to convert object.x to int while you're blitting(or drawing) it to a surface. With this, your object moves same amount in every second.
Second way is moving your object in every frame. This means your object's speed may change depending on your frame rate(for example, in a crowded scene, your framerate may drop and this makes your objects move slower).
def update_object():
object.x += object_vx
object.y += object.vy
# this is your main game loop
while running:
...
update_object()
BTW, I forgot to mention your object implementation. My preferred way to save coordinates in my objects is by using pygame.Rect's. pygame.Rect has 4 properties, x, y, height, and width. With this you can also hold your object's sprite's length and height.
For example:
character = pygame.Rect(10, 10, 20, 30)
character_image = pygame.image.load(...)
screen.blit(character_image, character) # screen is you surface
And when you want to change your character's coordinates:
character.x += x_amount
character.y += y_amount