We Keep Coding

The particle is not moving so what is the problem?

I follow a youtube video 'https://www.youtube.com/watch?v=cCiXqK9c18g' and in the video he make a class that represent a ball and he used pymunk to make a body and added it to the space and after that he created a method inside the ball class that will use pygame to draw the ball and I did almost like him
import pygame
import pymunk
pygame.init()
fps = 60
dt = 1/fps
dsX = 800 # screen width
dsY = 500 # screen height
display = pygame.display.set_mode((dsX, dsY))
space = pymunk.Space()
clock = pygame.time.Clock()
def convert_cor(point): # convet the coordinates from pymunk to pygame coordinates
return point[0], dsY - point[1]
class Particle: # v: velocity, pos: position[x, y], r: radius of particle(Circle)
def __init__(self, pos = [0, 0], v = [0, 0], r = 10, color = (255, 0, 0)):
self.pos = pos
self.v = v
self.r = r
self.color = color
self.body = pymunk.Body()
self.body.position = self.pos
self.body.velocity = self.v # this is the veclocity
self.shape = pymunk.Circle(self.body, self.r)
self.shape.dencity = 1
self.shape.elasticity = 1
space.add(self.body, self.shape)
def draw(self):
pygame.draw.circle(display, self.color, convert_cor(self.pos), self.r)
class Box: # thickness of the sides of the box and L1, L2, L3, L4 are the sides of the box
def __init__(self, thickness, color):
self.thickness = thickness
self.color = color
L1 = pymunk.Body(body_type = pymunk.Body.STATIC)
L2 = pymunk.Body(body_type = pymunk.Body.STATIC)
L3 = pymunk.Body(body_type = pymunk.Body.STATIC)
L4 = pymunk.Body(body_type = pymunk.Body.STATIC)
L1_shape = pymunk.Segment(L1, (0, 0), (dsX, 0), self.thickness)
L2_shape = pymunk.Segment(L2, (dsX, 0), (dsX, dsY), self.thickness)
L3_shape = pymunk.Segment(L3, (dsX, dsY), (0, dsY), self.thickness)
L4_shape = pymunk.Segment(L4, (0, dsY), (0, 0), self.thickness)
space.add(L1, L1_shape)
space.add(L2, L2_shape)
space.add(L3, L3_shape)
space.add(L4, L4_shape)
def draw(self):
pygame.draw.line(display, self.color, convert_cor((0, 0)), convert_cor((dsX, 0)), self.thickness * 2)
pygame.draw.line(display, self.color, convert_cor((dsX, 0)), convert_cor((dsX, dsY)), self.thickness * 2)
pygame.draw.line(display, self.color, convert_cor((dsX, dsY)), convert_cor((0, dsY)), self.thickness * 2)
pygame.draw.line(display, self.color, convert_cor((0, dsY)), convert_cor((0, 0)), self.thickness * 2)
def Sim(): # the infinite while loop as a function
box = Box(2, (0, 255, 255))
particle = Particle(pos =[dsX/2, dsY/2], v = [-200, 500]) # here i gave the position and the velocity
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
return
display.fill((255, 255, 255))
box.draw()
particle.draw()
clock.tick(fps)
space.step(dt)
pygame.display.update()
Sim()
pygame.quit()
The thing is, I did also a class that will add a rigid sides for the display and i drew the sides from the Box class using the method 'draw' The problem is in the time 5:58 in the video he gave the ball velocity and it start moving and in my code it does not move. any idea why it doen't move?
note: I called the ball particle in my code

You error is both a typo and using the wrong variable.
Inside your particles draw function...
# OLD
def draw(self):
pygame.draw.circle(display, self.color, convert_cor(self.pos), self.r)
# New
def draw(self):
pygame.draw.circle(display, self.color, convert_cor(self.body.position), self.r)
You have to use the body's position cause that is the position of the physics body in pymunk's space.
Secondly...
class Particle: # v: velocity, pos: position[x, y], r: radius of particle(Circle)
def __init__(self, pos, v, r=10, color=(255, 0, 0)):
...
# Old
self.shape.dencity = 1
# New
self.shape.density = 1
Since density was not set to anything Pymunk was having a divide by zero error so it wouldn't update the body's position.

self.body.position = self.pos
To be clear about the problem:
From what I could find in the documentation, pymunk.Body.position is a property; it expects you to pass either an ordinary Python tuple or a Vec2d (not a list, although anything it's relying on internally to handle a tuple probably handles a list just fine), and calls some internal code written in another programming language. The effect is that, instead of storing your list object and then making changes to the list (which would be visible in your class, since it would be the same object), it just gets the initial values out of your list, and then doesn't use the list object.
This means that when Pymunk applies physics calculations, self.body.position changes, but self.pos does not. So the current self.pos is useless; we can't use it to check the object position.
If you don't need to do that, then there is no need to create a self.pos at all - just feed self.body.position = pos directly, and make sure to use self.body.position when drawing.
If you do, I recommend using your own property instead of trying to set self.pos. Do the above, and then add to the class:
#property
def pos(self):
return self.body.position
And if you want to change the position from your code (but you probably shouldn't! Why else are you using the physics engine in the first place?), also add:
#pos.setter
def pos(self, value):
self.body.position = value

Pygame for possible trajectories planning for a car and make the car follow one of that path/trajectory

I have to create a visualization where I have to create a car (I considered to represent it as a rectangle) and develop trajectories for that car depending on its lateral & longitudinal acceleration. My problem is I am unable to create trajectories. I am doing this as a part of own project. Hence I have no idea if I am in the right direction or not. Guide me if I am wrong.
Problem1 : How do I show predicted path trajectories (beginner step to create only 8 trajectories and not many) ? Is a possible way to also create trajectories also like a curve using Pygame? If not, can I use a mix pf pygame and tkinter to create a mix of curved and straight line trajectories?
Problem2 : Make my rectangular car run along the chosen trajectory (curved line or straight line) or make it follow the path defined in trajectory.
Solutions Tried:
I have taken a rectangular sprite as a car with an idea that I can make it move around the desired trajectory. I am successful with sprite creation and moving it. But I am unable to show display any trajectory curve and make the car follow the path. I am not sure if I have to take trajectories also as Sprite or only car as Sprite is sufficient and trajectories as lines/curves?
Code of the above same explanation is as follows:
My Sprite Class :
class Vehicle(pygame.sprite.Sprite):
def __init__(self,x,y,slip_angle,length=4):
super().__init__()
width = 50
height = 50
self.image = pygame.Surface([width,height])
#Create a car
self.image.fill(RED)
self.image.set_colorkey(RED)
pygame.draw.rect(self.image, WHITE, [0, 0, width, height])
self.rect = self.image.get_rect()
#Parameters of car
self.position = position = Vector2(x, y)
self.velocity = Vector2(0.0, 0.0)
self.slip_angle = slip_angle
self.length = length
self.max_velocity = 20
self.brake_deceleration = 10
self.free_deceleration = 2
self.initial_velocity = 0
self.long_acceleration = 0.0
self.lat_acceleration = 0.0
self.acceleration = 0.0
self.steering = 0.0
def update(self,dt):
self.velocity += (self.acceleration * dt, 0)
self.velocity.x = max(-self.max_velocity, min(self.velocity.x, self.max_velocity))
if self.steering:
turning_radius = self.length / sin(radians(self.steering))
angular_velocity = self.velocity.x / turning_radius
else:
angular_velocity = 0
self.position += self.velocity.rotate(-self.angle) * dt
self.slip_angle += degrees(angular_velocity) * dt
Trajectory Class:
class trajectory(object):
def __init__(self,x,y):
self.x = x
self.y = y
def draw():
x_value = []
time = []
for acc in range(10):
for dt in range(0,10,0.05):
x = vehicle1.initial_velocity + (vehicle1.velocity*dt) + (0.5 * vehicle1.long_acceleration * dt* dt)
x_value.append(x)
time.append(dt)
coordinates = (x_value,time)
canvas_1 = Canvas(root,700,600,background='pink')
canvas_1.grid(row=0,column=1)
x1 = coordinates[acc]
y1 = coordinates[time]
canvas_1.create_line(x1,y1)
#pygame.draw.line(screen,GREEN,list(coordinates),(700, 600))
def update(self):
#self.angle = vehicle1.slip_angle*pi / 180
self.velocity_h = vehicle1.velocity*cos(angle)
self.velocity_v = vehicle1.velocity*sin(angle)
Pygame Main Logic :
#main Logic
proceed = True
#Capturing events till exit
while proceed:
for event in pygame.event.get():
if event.type == pygame.QUIT:
proceed = False
vehicle1.update(dt)
sprites_list.update(dt)
screen.fill(WHITE)
#screen.pygame.Surface.fill(color, rect=None, special_flags=0)
pygame.draw.line(screen, BLACK, [0, 0], [700, 300], 5)
# self.screen.blit(rotated, [20,30])
sprites_list.draw(screen)
pygame.display.flip()
clock.tick(60)
pygame.quit()
I thank you for your advices and support. Happy to accept any guidance

A simple re-working of your trajectory.draw() should sort it out. I noticed the initial x and y passed to the constructor don't seem to be used. Is it intended that the trajectory is always from ( 0, 0 ) or suchlike?
def draw( screen, initial_vel, vel, accel ):
coordinates = []
for acc in range(10):
for dt in range( 0, 10, 0.05 ):
x = initial_vel + ( vel * dt ) + ( 0.5 * accel * dt * dt )
coordinates.append( ( x, dt ) )
if ( len( coordinates ) > 1 ):
PINK = ( 255, 192, 203 )
pygame.draw.lines( screen, PINK, False, coordinates )
Pass your Window and Vehicle Velocities as a parameters when calling trajectory.draw(), rather than relying on global variables.
my_trajectory.draw( screen, vehicle1.initial_velocity, vehicle1.velocity, vehicle1.long_acceleration )

How to prevent fast moving objects passing through statics when calculating pi with colliding blocks

I am trying to implement a similar program to the following in Python using Pymunk and Pyglet. My current implementation works well at low velocities however at high speeds the block can pass through the static wall. This because in 1/60s clock cycle the block moves further than the thickness of the wall. I have seen others solve this by having a limiting speed however in my case this would not work as the velocity is important to calculate the value for PI. I would like to know if there is any way of preventing this from happening.
import pyglet
import pymunk
class Block:
"""
The class for a block
Mass: the mass the block
X: Initial x position
Y: Initial y position
PhysSpace: The physics space to add items to
RenderBatch: Batch to add block to
"""
def __init__(self, Mass, X, Y, PhysSpace, RenderBatch):
# Create body with given mass and infinite moment of inertia
self.Body = pymunk.Body(Mass, pymunk.inf)
# Set Body's position
self.Body.position = X, Y
# Create shape for body
BodyShape = pymunk.Poly.create_box(self.Body, size=(50, 50))
# Define shapes elasticity
BodyShape.elasticity = 1
# Add block to the physics space
PhysSpace.add(self.Body, BodyShape)
# Import block image
BlockImg = pyglet.image.load('res/sqr.png')
# Set anchor point of image to be the centre
BlockImg.anchor_x = BlockImg.width // 2
BlockImg.anchor_y = BlockImg.height // 2
# Create sprite for block
self.BlockSprite = pyglet.sprite.Sprite(BlockImg, x=self.Body.position.x, y=self.Body.position.y,
batch=RenderBatch)
def update(self):
# Set the position of the sprite to be equal to the position of the physics body
self.BlockSprite.position = self.Body.position
def give_velocity(self, velocity):
# Set velocity of the body
self.Body.velocity = (velocity, 0)
class Simulation(pyglet.window.Window):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
# Set background to be clear
pyglet.gl.glClearColor(1, 1, 1, 1)
# Set clock speed
pyglet.clock.schedule_interval(self.update, 1/60)
# Create batch to draw all the graphics with
self.Batch = pyglet.graphics.Batch()
# Create Title Label
self.TitleLabel = pyglet.text.Label(text='Block Collision Simulator', x=self.width / 2, y=self.height - 20,
batch=self.Batch, anchor_x='center', anchor_y='center', font_size=24,
color=(0, 0, 0, 255))
self.Counter = -2
self.CounterLabel = pyglet.text.Label('Counter = 0'.format(self.Counter), x=self.width / 2, y=self.height - 60, anchor_x='center',
anchor_y='center', font_size=24, color=(0, 0, 0, 255), batch=self.Batch)
# Initiate space for Physics engine
self.Space = pymunk.Space()
self.Handler = self.Space.add_default_collision_handler()
self.Handler.begin = self.coll_begin
# Create the ground in physics engine
Ground = pymunk.Poly.create_box(self.Space.static_body, size=(self.width, 20))
Ground.body.position = self.width / 2, 10
self.Space.add(Ground)
# Create the sprite for the ground
GroundImg = pyglet.image.load('res/ground.png')
self.GroundSprite = pyglet.sprite.Sprite(GroundImg, x=0, y=0, batch=self.Batch)
# Create Wall in physics engine
Wall = pymunk.Poly.create_box(self.Space.static_body, size=(20, self.height))
Wall.body.position = 10, self.height / 2
Wall.elasticity = 1
self.Space.add(Wall)
# Create the sprite for the wall
WallImg = pyglet.image.load('res/wall.png')
self.WallSprite = pyglet.sprite.Sprite(WallImg, x=0, y=0, batch=self.Batch)
self.BlockRight = Block(10000, 2 * (self.width / 3), 45, self.Space, self.Batch)
self.BlockRight.give_velocity(-100)
self.BlockLeft = Block(1, self.width / 3, 45, self.Space, self.Batch)
pyglet.app.run()
def coll_begin(self, arbiter, space, data):
self.Counter += 1
if self.Counter > 0:
self.CounterLabel.text = 'Counter: {}'.format(self.Counter)
return True
def on_draw(self):
self.clear()
self.Batch.draw()
def update(self, dt):
self.Space.step(dt)
self.BlockRight.update()
self.BlockLeft.update()

One way is as you write to limit the velocity. Another way is to call the step function with a smaller dt. (On the same note, you should almost always use a fixed value for the dt, that will help to keep the simulation stable).
One way to use smaller dt is to call the step function multiple times for each call to the update function. So you can try something like this:
def update(self, dt):
for _ in range(10):
self.Space.step(dt/10)
#self.Space.step(dt)
self.BlockRight.update()
self.BlockLeft.update()

Adding gravity to a bouncing ball using vectors

I have a gravity vector (in the form [r, theta]) which I add to my ball's velocity vector. For some reason, the ball doesn't return to the same height after bouncing, but instead slowly loses height sporadically. I am guessing there's some rounding error or something in a calculation I'm using, but I can't isolate the issue.
Here is my code. You need both files and pygame to run it. Sorry if it's a little confusing. I can comment anything some more if you want.
I added a marker whenever the ball reaches its max height so you guys what I mean. I want the ball to return to exactly the same height every time it bounces.
I took a little bit of unnecessary code out. The full program is under the pastebin links.
https://pastebin.com/FyejMCmg - PhysicsSim
import pygame, sys, math, tools, random, time
from pygame.locals import *
clock = pygame.time.Clock()
lines = []
class Particle:
def __init__(self,screen,colour, mass, loc, vel):
self.screen = screen
self.colour = colour
self.mass = mass
self.x = loc[0]
self.y = loc[1]
self.location = self.x,self.y
self.speed = vel[0]
self.angle = vel[1]
def update(self):
global lines
# add gravity
self.speed,self.angle = tools.add_vectors2([self.speed,self.angle], tools.GRAVITY)
# update position
dt = clock.tick(60)
self.x += self.speed * tools.SCALE * math.cos(self.angle) * dt
self.y -= self.speed * tools.SCALE * math.sin(self.angle) * dt
self.location = int(self.x),int(self.y)
# border checking
do = False
n=[]
if ((self.y+self.mass) > tools.SCREEN_HEIGHT):
self.y = tools.SCREEN_HEIGHT-self.mass
n = [0,1]
do = True
# adds position to array so max height so max height can be recorded
if (self.speed==0):
lines.append([self.screen, self.location, self.mass])
# bounce
if do:
#init, convert everything to cartesian
v = tools.polarToCartesian([self.speed, self.angle])
#final -> initial minus twice the projection onto n, where n is the normal to the surface
a = tools.scalarP(2*abs(tools.dotP(v,n)),n) #vector to be added to v
v = tools.add_vectors(v,a)
self.angle = tools.cartesianToPolar(v)[1] # does not set magnitude
# drawing
pygame.draw.circle(self.screen, self.colour, self.location, self.mass, 0)
# draws max height line
def draw_line(l):
screen = l[0]
location = l[1]
radius = l[2]
pygame.draw.line(screen, tools.BLACK, [location[0] + 15, location[1]-radius],[location[0] - 15, location[1]-radius])
def main():
pygame.init()
DISPLAY = pygame.display.set_mode(tools.SCREEN_SIZE,0,32)
DISPLAY.fill(tools.WHITE)
particles = []
particles.append(Particle(DISPLAY, tools.GREEN, 10, [100,100], [0,0]))
done = False
while not done:
global lines
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
sys.exit()
DISPLAY.fill(tools.WHITE)
for i in particles:
i.update()
for l in lines:
draw_line(l)
pygame.display.update()
main()
https://pastebin.com/Epgqka31 - tools
import math
#colours
WHITE = (255, 255, 255)
BLUE = ( 0, 0, 255)
GREEN = ( 0, 255, 0)
RED = ( 255, 0, 0)
BLACK = ( 0, 0, 0)
COLOURS = [WHITE,BLUE,GREEN,RED,BLACK]
#screen
SCREEN_SIZE = SCREEN_WIDTH,SCREEN_HEIGHT = 1000,700
#vectors
GRAVITY = [5.0, 3*math.pi/2] # not 9.8 because it seems too high
SCALE = 0.01
# converts polar coordinates to cartesian coordinates in R2
def polarToCartesian(v):
return [v[0]*math.cos(v[1]), v[0]*math.sin(v[1])]
# converts cartesian coordinates to polar coordinates in R2
def cartesianToPolar(v):
return [math.sqrt(v[0]**2 + v[1]**2), math.atan2(v[1],v[0])]
# dots two cartesian vectors in R2
def dotP(v1, v2):
return v1[0]*v2[0] + v1[1]*v2[1]
# multiplies cartesian vector v by scalar s in Rn
def scalarP(s,v):
v_=[]
for i in v:
v_.append(s*i)
return v_
# returns the sum of two cartesian vectors in R2
def add_vectors(v1, v2):
return [v1[0]+v2[0], v1[1]+v2[1]]
# returns the sum of two polar vectors in R2, equations from https://math.stackexchange.com/questions/1365622/adding-two-polar-vectors
def add_vectors2(v1,v2):
r1,r2,t1,t2 = v1[0],v2[0],v1[1],v2[1]
return [math.sqrt(r1**2 + r2**2 + 2*r1*r2*math.cos(t2-t1)), t1 + math.atan2(r2*math.sin(t2 - t1), r1 + r2*math.cos(t2 - t1))]

Your time interval, dt = clock.tick(60), is not a constant. If you change it to dt = 60 your program runs as expected.
Have a look a the Verlet Algorithm and implement it in your code. You are on the right track!

Pygame - Gravity Methods

I'm in the process of making a simple game in pygame. Its looking to be a platformer RPG. But that is neither final or relevant per this question. So far i have very little functionality in the game. Its just a skeleton at this point if that. My question is kind of two fold:
Whats the best (in terms of performance and flexibility) way to add gravity to classes in pygame?
What are the best practices for adding gravity in general? For example, do you just simply do a "if keyPressed == k_W then subtract 2pixels per tick from player-y for 20 ticks" or something with velocity in the up or negative-y direction?
I've seen other posts on adding gravity to games after the fact, where adding it really wasn't thought about during initial development. I want to add it in as early as possible so instead of adding gravity to other things, i can add other things to gravity. I'm going to continue to read up on this, so if you prefer to point me in the direction of some online resources, I'd much appreciate that as well!

Quick dislaimer: I do not know multiple ways to incorporate gravity, so I can not say which is "best". But, if you're fighting the performance battle in Python, you've probably fighting the wrong battle.
For gravity, you can use a vector system. Say a character jumps off the ground and has initial velocity of [5, -15] (negative y because positive y is down!), you can move your character's rect by this velocity every frame to simulate movement. To throw gravity into this, you need to add 9.8 to your y velocity component value every second. So 1 second in, the velocity will be about [5, -5]. This will have your character slow to a stop, and begin moving down.
For key pressed movement, I recommend using booleans. An example, upon pressing k_U , a variable that says you are moving up becomes True. Then, if this variable is True, you move him, say, [0, -5]. Upon keyup, set variable to false. Do this for north/east/south/west, and then you have a movement system in 4 directions, that moves you while you hold the key down.

I used the 1/2 mg^2 equation in this code, which has a snow like effect:
import math, sys, random, time
import pygame, inputbox
from pygame.locals import *
class flake:
def __init__(self, xpos, ypos, mass, color, drift):
self.xpos = xpos
self.ypos = ypos
self.mass = mass
self.rect = pygame.Rect(xpos, ypos, 2, 2)
self.checked = False
self.color = color
self.drift = drift
size = width, height = 510, 700
BLACK = (0,0,0)
WHITE = (255, 255, 255)
GREY = (128,128,128)
DARKGREY = (169,169,169)
SILVER = (192,192,192)
LIGHTGREY = (211,211,211)
LIGHTESTGREY = (220,220,220)
pygame.init()
screen = pygame.display.set_mode(size)
background = pygame.Surface(screen.get_size())
background = background.convert()
background.fill(BLACK)
def init():
global theSnow, snowColours, clock, startrange
theSnow = []
snowColours = []
snowColours.append(WHITE)
snowColours.append(GREY)
snowColours.append(DARKGREY)
snowColours.append(SILVER)
snowColours.append(LIGHTGREY)
snowColours.append(LIGHTESTGREY)
for c in range(2000):
mass = 0.0
mass = float(random.randint(1,8) / 100.0)
xpos = random.randint(0,width)
ypos = random.randint(0,5)
ypos = -ypos
drift = ypos/10.0
colour = snowColours[random.randint(0,5)]
f = flake(xpos, ypos, mass, colour, drift)
theSnow.append(f)
print "flake x = " + str(f.xpos) + " y = " + str(f.ypos) + " mass = " + str(f.mass)
startrange = 200
clock = pygame.time.Clock()
def run():
global theSnow, clock
global startrange
newrange = 0
while True:
events = pygame.event.get()
for event in events:
if event.type == pygame.QUIT:
sys.exit()
keys=pygame.key.get_pressed()
if keys[K_q]:
return
g = 3
for count in range(startrange):
yinc = 0.0
yuncertainty = float(random.randint(1,5)/10.0)
yinc = float(0.5 * theSnow[count].mass * (g*g)) + yuncertainty
theSnow[count].ypos += yinc
xuncertainty = random.randint(1,10)
if xuncertainty > 4:
theSnow[count].xpos += theSnow[count].drift
else:
theSnow[count].xpos -= theSnow[count].drift
theSnow[count].rect = pygame.Rect(theSnow[count].xpos, theSnow[count].ypos, 2,2)
if not theSnow[count].checked:
if theSnow[count].ypos > 30:
for c in range(newrange, startrange):
print " c= " + str(c)
theSnow[c].checked = True
if startrange < 2000:
startrange += 100
newrange = startrange - 100
print " newrange = " + str(newrange)
print " startrange = " + str(startrange)
update()
pygame.time.wait(10)
#clock.tick(10)
def update():
global theSnow, startrange
background.fill(BLACK)
for count in range(startrange):
pygame.draw.rect(background, theSnow[count].color, theSnow[count].rect)
screen.blit(background, (0, 0))
pygame.display.flip()
if __name__ == "__main__":
init()
run()