# Spiral

Inspired by a recent Slow Mo Guys video, I wrote a simulation for the shown effect. I think it looks pretty neat…

#### Controls

• Up arrow increases the number of emitted particles
• Down arrow decreases the number of emitted particles
• Space saves a screenshot

``````# Python 2.7.7 Code
# Pygame 1.9.1 (for Python 2.7.7)
# Jonathan Frech 23rd of October, 2015
#         edited 24th of October, 2015``````

``````# importing needed modules
import pygame, sys, time, math, os, random, datetime

""" CLASSES """
# dummy class for global variables
class dummy():
pass

class entity():
def __init__(self):
self.pos = [main.WIDTH/2, main.HEIGHT/2]
self.spin = 0
self.spinpertick = 2
self.pixels = []

self.color = [50, 50, 50]
self.pixelcolor = [255, 0, 0]

def tick(self):
self.spin += self.spinpertick

n = main.N
for _ in range(0, int(n)):
self.pixels.append(intpos(getCirclePos(self.pos, self.radius, 360. / n * _ + self.spin)))
#self.pixels.append(getCirclePos(self.pos, self.radius, 360. / n * _))

pixels = []
for _ in self.pixels:
vec = vecConvert(_, self.pos)
vecl = vecLen(vec)
if vecl != 0:
vec0 = vecMultiply(vec, 1. / vecl)
vecn = vecMultiply(vec0, vecl*1.05)
p = vecGetPoint(vecn, self.pos)
if p[0] > 0 and p[1] > 0 and p[0] < main.WIDTH and p[1] < main.HEIGHT:
pixels.append(p)

self.pixels = pixels

def render(self, _surface):
#pygame.draw.polygon(_surface, [0, 0, 20], self.pixels)

for _ in self.pixels:
#_surface.set_at(intpos(_), self.pixelcolor)
pygame.draw.circle(_surface, self.pixelcolor, intpos(_), 2)

""" FUNCTIONS """
# gets the position on a circle with a position, radius and an angle
return [
]

# returns an integer version of given positon
def intpos(_pos):
return [int(_pos[0]), int(_pos[1])]

# basic vector functions
def vecConvert(p1, p2):
return [p2[0] - p1[0], p2[1] - p1[1]]
def vecLen(vec):
return math.sqrt( (vec[0]**2) + (vec[1]**2) )
def vecMultiply(vec, n):
return [vec[0] * n, vec[1] * n]
def vecGetPoint(vec, point):
return [point[0] + vec[0], point[1] + vec[1]]
return [vec1[0] + vec2[0], vec1[1] + vec2[1]]

# saves the current surface
def savesurf():
try:
if not os.path.isdir(main.SAVEPATH):
os.mkdir(main.SAVEPATH)

name = "img" + str(len(os.listdir(main.SAVEPATH))) + ".png"
pygame.image.save(main.SURF, main.SAVEPATH + name)
except:
pass

# quits the program
def quit():
sys.exit()

""" TICK; RENDER """
# tick function
def tick():
# handle events
for event in pygame.event.get():
if event.type == pygame.QUIT:
quit()

if event.type == pygame.KEYDOWN:
if event.key == pygame.K_SPACE:
savesurf()
if event.key == pygame.K_UP:
main.N += 1
if event.key == pygame.K_DOWN:
main.N -= 1
if main.N < 2:
main.N = 2

for _ in main.ENTITIES:
_.tick()

# render function
def render():
# fill
main.SURF.fill([0, 0, 0])

for _ in main.ENTITIES:
_.render(main.SURF)

# blit and flip
main.SCREEN.blit(main.SURF, [0, 0])
pygame.display.flip()

""" INIT """
# initialize program
def init():
main.WIDTH, main.HEIGHT = 1080, 720
main.SIZE = [main.WIDTH, main.HEIGHT]
main.SCREEN = pygame.display.set_mode(main.SIZE)
main.SURF = pygame.Surface(main.SIZE)

main.CAPTION = "Spiral"
main.TICKS = 0

main.N = 2

main.SAVEPATH = os.getcwd() + "/out/"
main.ENTITIES = [entity()]

# functions
pygame.display.set_caption(main.CAPTION)

""" RUN """
# run function (uses tick() and render())
def run():
ticksPerSecond = 60
lastTime = time.time() * 1000000000
nsPerTick =  1000000000.0 / float(ticksPerSecond)

ticks = 0
frames = 0

lastTimer = time.time() * 1000
delta = 0.0

while True:
now = time.time() * 1000000000
delta += float(now - lastTime) / float(nsPerTick)
lastTime = now
shouldRender = False

while delta >= 1:
ticks += 1
main.TICKS += 1
tick()
delta -= 1
shouldRender = True

if shouldRender:
frames += 1
render()

if time.time() * 1000 - lastTimer >= 1000:
lastTimer += 1000

# debug
#print("Frames: " + str(frames) + ", ticks: " + str(ticks))

frames = 0
ticks = 0

# main variable
main = dummy()
init()

# start program
run()``````