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Finding proper X/Y coordinate modifiers with given angle in Python/Pygame

I am trying to make a sprite move directly towards the mouse, utilizing the angle between them. This angle is found via the atan2 function. While this angle works fine for rotating the sprite towards the mouse, the sprite moves in the wrong directions depending on the quadrant of the given angle. It will sometimes freeze up in one quadrant, or move directly opposite the mouse.
I am using basic Trig functions to find the angle, and calculate proper additions to the X and Y variables of the sprite. It is also important to note that the angle I calculate, while it doesn't work for movement, does work perfectly for rotation. What's odd is that I pass the X-difference between the two spots, and THEN the Y-difference, which is the opposite of how the inverse tangent function is supposed to be handled. Therefore, I'm not even sure how this angle has been making rotation work correctly.
I've attempted to pass the Y-difference and the X-difference (in that order) into the atan2 function. However, this causes the rotation on my sprite to be wrong, pointing me towards the idea that the angle as a whole is also incorrect. I've also tried following along with numerous other programs, all of which use the same formulas as me. However, these don't work, even when I change the order of the arguments to the atan2 function to match the example programs.
def main():
ExitLoop = False
image = IMAGELOADER.AllImages["Fighter1"]
image2 = IMAGELOADER.AllImages["Fighter2"]
Fighter1 = FighterClass.Fighter(image,(700,700))
Fighter2 = FighterClass.Fighter(image2,(300,300))
while not ExitLoop:
ScreenController.Refresh()
mouse_pos = pygame.mouse.get_pos()
Fighter2.set_x(mouse_pos[0]-32)
Fighter2.set_y(mouse_pos[1]-32)
angle = math.atan2(Fighter1.get_x()-mouse_pos[0]+32, Fighter1.get_y()-mouse_pos[1]+32)
degrees_angle = math.degrees(angle)
Fighter1.rotate(degrees_angle)
xval = Fighter1.get_x()
yval = Fighter1.get_y()
speed = Fighter1.get_speed()
changex = (speed*math.cos(angle))
changey = (speed*math.sin(angle))
Fighter1.set_x(xval+changex)
Fighter1.set_y(yval+changey)
for event in pygame.event.get():
if event.type == pygame.QUIT:
ExitLoop = True
ScreenController.Draw(Fighter1.get_image(),Fighter1.get_rect(),False)
ScreenController.Draw(Fighter2.get_image(),Fighter2.get_rect(),False)
ScreenController.DisplayUpdate()
clock.tick(60)
Class Code (Relevant to the fighter class)
import pygame
import WoodysFunctions
class Fighter(pygame.sprite.Sprite):
def __init__(self,image,XnY):
pygame.sprite.Sprite.__init__(self)
self.image = image
self.__image_source = image
self.rect = self.image.get_rect()
self.__mask = pygame.mask.from_surface(self.image)
self.rect.x = XnY[0]
self.rect.y = XnY[1]
self.__speed = 1
def get_image(self):
return self.image
def get_rect(self):
return self.rect
def get_mask(self):
return self.__mask
def get_x(self):
return self.rect.x
def get_y(self):
return self.rect.y
def get_speed(self):
return self.__speed
def set_image(self,value):
self.image = value
def set_rect(self,value):
self.__rect = value
def set_mask(self,value):
self.__mask = value
def set_x(self,value):
self.rect.x = value
def set_y(self,value):
self.rect.y = value
def set_speed(self,value):
self.__speed = value
def rotate(self,angle):
old_center = self.rect.center
self.image = pygame.transform.rotate(self.__image_source,angle)
self.rect = self.image.get_rect()
self.rect.center = old_center
Expected output: Sprite moves straight towards the mouse
Actual behavior: Sprite moves in wrong directions, with behavior showing patterns depending on quadrant of calculated angle.
Edit:
I changed the program so that the X and Y variables of the sprite are stored in variables separate from the rect object. This prevents decimal truncation. I also recalculated the angle between the sprite and the mouse pointer after the rotation code is finished. In the recalculation, the X and Y difference parameters are swapped to match the inverse tangent function instead of the inverse cotangent function. This recalculated angle is used for angular movement, and the first angle, with the X difference passed first, is used for rotation. It is important to note that after I calculated the changeX and changeY variables using the recalculated angle (with the Y difference passed first), I multiplied them by -1, as otherwise the sprite will move away from the mouse pointer.

I cannot be 100% sure, but I think the problem is that pygame.Rect stores position as integers, because it's supposed to store coordinates and dimensions in pixel unit, and of course you cannot paint half pixel.
Since you are dealing with any angle and trigonometric functions, you end with floats which are truncated when you do:
def set_x(self,value):
self.rect.x = value
Here, if value is 1.4, self.rect.x becomes 1. So you lose "accuracy."
This loss of accuracy is propagated each iteration of the main loop (each frame), resulting in an unexpected motion direction.
The best solution is to store all your value in a separate data structure and update the rect attribute only for drawing in the screen.

Move in degrees pygame

I am making a utility for myself to easily translate degrees to x and y cordinates in my games and I got stuck on a problem; trying to move the player in degrees across the screen. I found multiple formulas that didn't work and I need some help. Here is my code that I found:
def move(degrees, offset):
x = math.cos(degrees * 57.2957795) * offset # 57.2957795 Was supposed to be the
y = math.sin(degrees * 57.2957795) * offset # magic number but it won't work.
return [x, y]
I then ran this:
move(0, 300)
Output:
[300.0, 0.0]
and it worked just fine, but when I did this:
move(90, 300)
it outputted this:
[-89.8549554331319, -286.22733444608303]

Your approach is almost correct. You should use radians for sin/cos functions. Here is a method I commonly use in C++ (ported to python) for 2D movement.
import math
def move(degrees, offset)
rads = math.radians(degrees)
x = math.cos(rads) * offset
y = math.sin(rads) * offset
return x, y

The number is correct, but the operation is wrong. In order to convert degrees to radians you need to divide by 180 degrees per half-circle and then multiply by pi radians per half-circle. This is equivalent to dividing by the constant you have.

You can use the from_polar method of the pygame.math.Vector2 class to set the polar coordinates of a vector. Then you can use this vector to adjust the position of a sprite or rect.
import pygame as pg
from pygame.math import Vector2
def move(offset, degrees):
vec = Vector2() # Create a zero vector.
vec.from_polar((offset, degrees)) # Set its polar coordinates.
return vec
pg.init()
screen = pg.display.set_mode((640, 480))
clock = pg.time.Clock()
BG_COLOR = pg.Color('gray12')
BLUE = pg.Color('dodgerblue1')
rect = pg.Rect(300, 200, 30, 20)
done = False
while not done:
for event in pg.event.get():
if event.type == pg.QUIT:
done = True
elif event.type == pg.KEYDOWN:
if event.key == pg.K_SPACE:
# Use the vector that `move` returns to move the rect.
rect.move_ip(move(50, 90))
screen.fill(BG_COLOR)
pg.draw.rect(screen, BLUE, rect)
pg.display.flip()
clock.tick(30)
pg.quit()

Dealing with Sprites and Collisions Using Pygame

I am learning python using pygame and I am working on something that involves sprites and collisions. I've looked at some examples but I still don't quite understand it. What I am attempting to do is to be able to add sprites(a ball) when the user presses the "=" key and also be able to remove the last sprite added when pressing "-". I am not able to remove just the last one, I have only been able to remove all of them.
So far I have been able to add the balls to the window and have them bounce off the walls and one another(sort of). When 2 balls collide, they don't completely touch yet they bounce off. Sometimes the balls get stuck and won't move and sometimes the balls bounce off the frame which they aren't suppose to.
Its my first time working with sprite groups and would appreciate any help/guidance into making this work smoothly.Thanks.
The code:
ball.py
import pygame
from pygame.locals import *
class Ball(pygame.sprite.Sprite):
def __init__(self, x, y, vx, vy):
super().__init__();
self.image = pygame.image.load("ball.png").convert()
self.image.set_colorkey(pygame.Color(0, 0, 0))
self.rect = self.image.get_rect()
self.rect.x = x
self.rect.y = y
self.vx = vx
self.vy = vy
def draw(self, SCREEN):
SCREEN.blit(self.image, (self.rect.x, self.rect.y))
def move(self, SCREEN, balls):
l_collide = self.rect.x + self.image.get_width() + self.vx > SCREEN.get_width()
r_collide = self.rect.x + self.vx < 0
t_collide = self.rect.y + self.vy < 0
b_collide = self.rect.y + self.image.get_height() + self.vy > SCREEN.get_height()
a = pygame.sprite.spritecollide(self, balls, False, False)
if len(a) > 1:
self.vx *= -1
self.vy *= -1
if l_collide or r_collide:
self.vx *= -1
if t_collide or b_collide:
self.vy *= -1
self.rect.x += self.vx
self.rect.y += self.vy
ball_animation.py
import pygame
import sys
import random
import math
from pygame.locals import *
from ball.ball import Ball
from random import randint
def ball_list(num):
ball_list = pygame.sprite.Group()
for x in range(num):
rand_x = random.randint(0,400)
rand_y = random.randint(0,400)
vx = 4
vy = 5
ball_list.add(Ball(rand_x, rand_y, vx, vy))
return ball_list
def main():
pygame.init()
FPS = 30
FPS_CLOCK = pygame.time.Clock()
# COLOR LIST
BLACK = pygame.Color(0, 0, 0)
# Code to create the initial window
window_size = (500, 500)
SCREEN = pygame.display.set_mode(window_size)
# set the title of the window
pygame.display.set_caption("Bouncing Ball Animation")
# change the initial background color to white
SCREEN.fill(BLACK)
balls = ball_list(0)
while True: # <--- main game loop
for event in pygame.event.get():
if event.type == QUIT: # QUIT event to exit the game
pygame.quit()
sys.exit()
if event.type == KEYDOWN:
if event.key == K_EQUALS:
balls.add(Ball(randint(0,400),randint(0,400), 4,5))
if event.key == K_MINUS:
try:
balls.remove()
except IndexError:
print('There is no balls to take!')
SCREEN.fill(BLACK)
for x in balls:
x.move(SCREEN,balls)
x.draw(SCREEN)
pygame.display.update() # Update the display when all events have been processed
FPS_CLOCK.tick(FPS)
if __name__ == "__main__":
main()

Removing Sprites on Press
The problem is sprite.Group.remove(sprites) wants you to specify which sprites it should remove. sprites here should be a sprite/list of sprites that you want to remove from the group. This means to remove the last ball added on key press you need to keep a list of the ball sprites and pop() the most recently added item from it, and then use the result of the pop() as the sprite to remove from the group. sprite.Group has a .sprites() method which returns a list of all sprites in the group, in the order they were added. This list is generated from the group and is not actually an interface with it, so doing things to this list won't affect the group. We can still however use it to get the last added sprite. Here is what it looks like:
elif event.key == K_0:
try:
sprite_list = balls.sprites()
to_remove = sprite_list[-1] # Get last element of list
balls.remove(to_remove)
except IndexError:
print('There is no balls to take!')
Collisions
So this is a bit more involved and not so simple to fix in your code. To understand what the problem is, look at what your collision velocity adjustments are actually doing for the screen border case.
l_collide = self.rect.x + self.image.get_width() + self.vx > SCREEN.get_width()
r_collide = self.rect.x + self.vx < 0
t_collide = self.rect.y + self.vy < 0
b_collide = self.rect.y + self.image.get_height() + self.vy > SCREEN.get_height()
#################
if l_collide or r_collide:
self.vx *= -1
if t_collide or b_collide:
self.vy *= -1
Consider a single time-step in your code. We check to see if the sprite is sitting over the edge of the boundaries by any amount. If its hanging over, we reverse the velocity. There is a case where your edge checking will get you into trouble. If your self.vx is less than the difference between your current position X and the boundary of the x dimension, you will reverse your speed, travel self.vx back towards the boundary, but not make it past. In the next time-step, you will see that you are still over the boundary, and your program will again reverse self.vx, actually sending you away from the boundary. In this case you will bound back and forth each time-step by self.vx. Normally this wouldn't happen in your code, except for when you spawn a new ball sprite over the boundary further than your self.vx or self.vy for that ball. This can be remedied by making sure you don't spawn balls off the edges, or better yet, only reversing your velocity if you need to.
if (l_collide and self.vx>0) or (r_collide and self.vx<0):
self.vx *= -1
if (t_collide and self.vy<0) or (b_collide and self.vy>0):
self.vy *= -1
Notice here we only reverse the velocity if we are over the edge AND the velocity is headed deeper in that direction. Now for your sprites you have two options, just like with the boundaries:
Only initiate a new ball in empty space where it cannot collide.
Implement some way to calculate the correct velocity adjustment and only apply it if the velocity is headed in the opposite direction.
From what I read in the documentation, sprite.Group looks like it is meant for checking if sprites are overlapping, and not for physics simulation. I recommend doing some research on 2d physics simulation to get a nice conceptualization of what information you should want to communicate between objects. I'm sure there are some nice tutorials out there.
Finally, to address your other question about why they are colliding when they don't appear to be touching. sprite.spritecollide is returning which sprites have rectangles that intersect. If your ball.png is color keyed for transparency, this does not affect the rect of the sprite. Pygame appears to have functionality implemented designed to handle this problem in the collided keyword of sprite.spritecollide:
pygame.sprite.spritecollide()
Find sprites in a group that intersect another sprite.
spritecollide(sprite, group, dokill, collided = None) -> Sprite_list
The collided argument is a callback function used to calculate if two sprites >are colliding. it should take two sprites as values, and return a bool value >indicating if they are colliding. If collided is not passed, all sprites must >have a “rect” value, which is a rectangle of the sprite area, which will be >used to calculate the collision.
collided callables:
collide_rect
collide_rect_ratio
collide_circle
collide_circle_ratio
collide_mask
That's from the pygame documentation. The documentation for the collide_circle function states that your sprite should have a radius attribute, or else one will be calculated to fit the entire rectangle inside a circle. As such, in your Ball.__init__ function I would recommend adding:
self.radius = self.rect.width/2
This will make collide_circle use a radius that approximates your ball image, assuming it is centered and circular and occupies the entire image. Next, you must add the collision specification to your collision check by changing:
a = pygame.sprite.spritecollide(self, balls, False, False)
to
a = pygame.sprite.spritecollide(self, balls, False, pygame.sprite.collide_circle)
If you solve the problem of not spawning new ball objects inside each other, this should all work nicely. If you can't get them to spawn inside each other, think about a different data-structure or different way of collision checking to get the results you want. Best of luck!

I can see two questions in your text
You want to only remove one sprite, rather than all the sprites in the spritegroup
If you look at the pygame documentation, you can see that spritegroup.remove has an optional argument. You can remove a single sprite by putting your desired sprite as the argument, such as myspritegroup.remove(mysprite).
You have issues with the colliding
Your collision works for me as long as the balls don't spawn on top of each other on creation which you can simply check. Good luck :)

PyGame-Character Goes Off Screen

I am trying to make a game with pygame but I can't figure out how to keep my character from going off screen(set a limit). I have a .png image controlled by user input, but it's possible for the character to go off the visible screen area normally. I can't figure out how to do this. I made a rectangle around the window, (pygame.draw.rect) but I can't assign the rect to a variable so I can create a collision. I also tried this:
if not character.get_rect() in screen.get_rect():
print("error")
But it didn't work, just spammed the python console with "error" messages.
(i checked the other post with this question but nothing worked/didn't get it)
So my question is, how can I keep my character from going offscreen, and which is the best way to do that?
~thanks
EDIT: My game doesn't have a scrolling playfield/camera. (just a fixed view on the whole window)

if not character.get_rect() in screen.get_rect():
print("error")
I see what you are trying here. If you want to check if a Rect is inside another one, use contains():
contains()
test if one rectangle is inside another
contains(Rect) -> bool
Returns true when the argument is completely inside the Rect.
If you simply want to stop the movement on the edges on the screen, an easy solution is to use clamp_ip():
clamp_ip()
moves the rectangle inside another, in place
clamp_ip(Rect) -> None
Same as the Rect.clamp() [Returns a new rectangle that is moved to be completely inside the argument Rect. If the rectangle is too large to fit inside, it is centered inside the argument Rect, but its size is not changed.] method, but operates in place.
Here's a simple example where you can't move the black rect outside the screen:
import pygame
pygame.init()
screen=pygame.display.set_mode((400, 400))
screen_rect=screen.get_rect()
player=pygame.Rect(180, 180, 20, 20)
run=True
while run:
for e in pygame.event.get():
if e.type == pygame.QUIT: run = False
keys = pygame.key.get_pressed()
if keys[pygame.K_w]: player.move_ip(0, -1)
if keys[pygame.K_a]: player.move_ip(-1, 0)
if keys[pygame.K_s]: player.move_ip(0, 1)
if keys[pygame.K_d]: player.move_ip(1, 0)
player.clamp_ip(screen_rect) # ensure player is inside screen
screen.fill((255,255,255))
pygame.draw.rect(screen, (0,0,0), player)
pygame.display.flip()

When you used pygame.draw.rect, you didn't actually create a "physical" boundary- you just set the colour of the pixels on the screen in a rectangular shape.
If you know the size of the screen, and the displacement of all of the objects on the screen (only applicable if your game has a scrolling playfield or camera), then you can do something like this:
# In the lines of code where you have the player move around
# I assume you might be doing something like this
if keys[pygame.K_RIGHT]:
player.move(player.getSpeed(),0) # giving the x and y displacements
if keys[pygame.K_LEFT]:
player.move(-player.getSpeed(),0)
...
class Player:
...
def move(self, dx, dy):
newX = self.x + dx
newY = self.y + dy
self.x = max(0, min(newX, SCREEN_WIDTH)) # you handle where to store screen width
self.y = max(0, min(newY, SCREEN_HEIGHT))
Note that a useful tool for you to get the size of the Pygame window is pygame.display.get_surface().get_size() which will give you a tuple of the width and height. It is still better, however, to avoid calling this every time you need to know the boundaries of the player. That is, you should store the width and height of the window for later retrieval.

Here's a simple control code that I use in my games to keep sprites from going off the screen:
# Control so Player doesn't go off screen
if self.rect.right > WIDTH:
self.rect.right = WIDTH
if self.rect.left < 0:
self.rect.left = 0
if self.rect.bottom > HEIGHT:
self.rect.bottom = HEIGHT
if self.rect.top < 0:
self.rect.top = 0
WIDTH and HEIGHT are constants that you define to set the size of your screen. I hope this helps.

Problem with 2D collision detection from beginner

I've taken an introductory course in Computer Science, but a short while back I decided to try and make a game. I'm having a problem with collision detection. My idea was to move an object, and if there is a collision, move it back the way it came until there is no longer a collision. Here is my code:
class Player(object):
...
def move(self):
#at this point, velocity = some linear combination of (5, 0)and (0, 5)
#gPos and velocity are types Vector2
self.hitBox = Rect(self.gPos.x, self.gPos.y, 40, 40)
self.gPos += self.velocity
while CheckCollisions(self):
self.gPos -= self.velocity/n #see footnote
self.hitBox = Rect(self.gPos.x, self.gPos.y, 40, 40)
...
def CheckCollisions(obj):
#archList holds all 'architecture' objects, solid == True means you can't walk
#through it. colliderect checks to see if the rectangles are overlapping
for i in archList:
if i.solid:
if i.hitBox.colliderect(obj.hitBox):
return True
return False
*I substituted several different values for n, both integers and floats, to change the increment by which the player moves back. I thought by trying a large float, it would only move one pixel at a time
When I run the program, the sprite for the player vibrates very fast over a range of about 5 pixels whenever I run into a wall. If I let go of the arrow key, the sprite will get stuck in the wall permanently. I wondering why the sprite is inside the wall in the first place, since by the time I blit the sprite to the screen, it should have been moved just outside of the wall.
Is there something wrong with my method, or does the problem lie within my execution?

Looks like you're setting the hitbox BEFORE updating the position. The Fix seems simple.
Find:
self.hitBox = Rect(self.gPos.x, self.gPos.y, 40, 40)
self.gPos += self.velocity
Replace:
self.gPos += self.velocity
self.hitBox = Rect(self.gPos.x, self.gPos.y, 40, 40)
Other Suggestions: What you should do is check the position BEFORE you move there, and if it's occupied, don't move. This is untested so please just use this as psuedocode intended to illustrate the point:
class Player(object):
...
def move(self):
#at this point, velocity = some linear combination of (5, 0)and (5, 5)
#gPos and velocity are types Vector2
selfCopy = self
selfCopy.gPos += self.velocity
selfCopy.hitBox = Rect(selfCopy.gPos.x, selfCopy.gPos.y, 40, 40)
if not CheckCollisions(selfCopy)
self.gPos += self.velocity
...
def CheckCollisions(obj):
#archList holds all 'architecture' objects, solid == True means you can't walk
#through it. colliderect checks to see if the rectangles are overlapping
for i in archList:
if i.solid:
if i.hitBox.colliderect(obj.hitBox):
return True
return False