Thanks Alan.
It is partly due to curiosity but I also wanted to have a common update
method. And as I almost always use the x+= some code, y+=some code for
animation stuff I wanted to know how it could be done using this method
rather than finding each position separately and assigning with x= some
code, y = some code (new position).
But here is STILL something curious in this whole matter.
If I update the rect positions with
obj.rect.x+ = some code
obj.rect.y+ = some code
then the rotation are NOT circular.
BUT
if I use
obj.x += some code
obj.y += some code
and then do
obj.rect.x, obj.rect.y = obj.x, obj.y
then the rotation works correct!!
This is really weird and I have no explanation as to why this happens!!!
Can you or anyone else explain this strange behaviour? After all a position
is a position.(at least that;s how I understand as long as you stick with
the same coordinate through out.)
The code is below.
import sys, os, pygame, itertools
from math import sin,cos,pi
from pygame.locals import *
SCREENW = 800
SCREENH = 700
class object_factory(pygame.sprite.Sprite):
def __init__(self, image, xpos = 0, ypos = 0):
"""Constructor"""
pygame.sprite.Sprite.__init__(self)
self.image = image
self.mask = pygame.mask.from_surface(self.image) # pixelmask
self.rect = self.image.get_rect()
self.rect.x = xpos
self.rect.y = ypos
self.x=xpos
self.y=ypos
pygame.init()
clock = pygame.time.Clock()
os.environ['SDL_VIDEO_WINDOW_POS'] = "%d,%d" % (50,50) #Set window position
SCREEN = pygame.display.set_mode((SCREENW, SCREENH))
clock = pygame.time.Clock()
pygame.display.set_caption('rotating object')
ball = pygame.image.load("ball.jpg")
pin=pygame.image.load("center.jpg");
platforms = pygame.sprite.Group()
center_x = SCREENW/2
center_y = SCREENH/2
radius = 200
angle = pi/4 # starting angle 45 degrees
omega = 0.1 #Angular velocity
for _ in itertools.repeat(None, 6):
xpos = center_x + radius * cos(angle) #Starting position x
ypos = center_y - radius * sin(angle) #Startinh position y
obj = object_factory(ball, xpos, ypos)
obj.angle = angle
obj.omega = omega #angula velocity
obj.radius = radius
platforms.add(obj)
angle += pi/.5
#----------------------------------------------------------------------
while True:
clock.tick(24)
pygame.event.pump()
keys = pygame.key.get_pressed()
for event in pygame.event.get():
if event.type == QUIT or (event.type == KEYDOWN and event.key ==
K_ESCAPE):
pygame.quit()
sys.exit()
SCREEN.fill((0, 0, 0))
SCREEN.blit(pin,(center_x - pin.get_width() / 2, center_y -
pin.get_height() / 2))
pygame.draw.circle(SCREEN, (0, 0, 255), (center_x, center_y), radius, 2)
for b in platforms:
b.angle+=b.omega
#Rect Base Rotation
#b.rect.x += b.radius * b.omega * cos(b.angle + pi / 2)
#b.rect.y -= b.radius * b.omega * sin(b.angle + pi / 2)
#SCREEN.blit(ball,(b.rect.x,b.rect.y))
#Normal Rotation
b.x+= b.radius * b.omega * cos(b.angle + pi / 2)
b.y-= b.radius * b.omega * sin(b.angle + pi / 2)
b.rect.x, b.rect.y = b.x - b.rect.width / 2, b.y - b.rect.height / 2
#SCREEN.blit(ball,(b.x,b.y)) # this and the line below gives the
same result
#SCREEN.blit(ball, (b.rect.x, b.rect.y))
platforms.update()
platforms.draw(SCREEN)
pygame.time.wait(100)
pygame.display.update()
On Thu, Apr 30, 2015 at 12:25 AM, Alan Gauld <alan.ga...@btinternet.com>
wrote:
> On 29/04/15 19:37, diliup gabadamudalige wrote:
>
>> I do not understand how Alan does not get the code
>>
>
>
> Replying off list.
>
> I don't get it because text based email systems often strip out attachments
> since they are a security risk. As the name says they are *text* based.
>
> However, now that I've seen it and I see your solution I can better
> understand
> what you were trying to ask, which was the solution to a very specific
> scenario.
>
> I'm still not sure why you wanted to use augmented assignment, other
> than curiosity perhaps, but at least I now see what you were trying to do.
> Thanks for posting the solution.
>
>
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
>
>
--
Diliup Gabadamudalige
http://www.diliupg.com
http://soft.diliupg.com/
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