Pygame's arc to be used as a sprite

Question

I am trying to use the pygame.draw.arc() as a sprite, but its not displaying on the screen. I can achieve the same effect by writing same code in the main loop, but once I try to create a sprite, the effect is not being displayed.

(One part in the main-loop can be un-commented to see the desired effect as well.)

Any pointers could be of great help.

import pygame
import random
import math


BLACK    = (   0,   0,   0)
WHITE    = ( 255, 255, 255)
RED      = ( 255,   0,   0)

SCREEN_WIDTH = 513
SCREEN_HEIGHT = 513
class Block(pygame.sprite.Sprite):
    def __init__(self, color, width, height):
        pygame.sprite.Sprite.__init__(self)

        self.color = color
        self.image = pygame.Surface([width, height])

        self.image.fill(WHITE)
        self.image.set_colorkey(WHITE)

        self.center_x = SCREEN_WIDTH/2-15
        self.center_y = SCREEN_HEIGHT/2-15
        # Draw the ellipse, THIS WORKS PERFECTLY
        #pygame.draw.ellipse(self.image, color, [0, 0, width, height])

        self.i=0
        #THIS DOESN'T WORK FOR SOME REASON
        pygame.draw.arc(self.image, (0,255,255),(25,25,450,450),0+(self.i*math.pi)/180,math.pi/6 +(self.i*math.pi)/180,10)
        self.rect = self.image.get_rect()
        self.angle = 0
        self.radius = 210
        self.speed = 0.05

    def update(self):
        self.i += self.speed


pygame.init() 
screen = pygame.display.set_mode([SCREEN_WIDTH, SCREEN_HEIGHT])

all_sprites_list = pygame.sprite.Group()

block = Block(BLACK, 20, 15) 
all_sprites_list.add(block) 

done = False

clock = pygame.time.Clock()
i=0
while not done:
    for event in pygame.event.get():  
        if event.type == pygame.QUIT: # 
            done = True  
    screen.fill(WHITE)
    all_sprites_list.update()

    all_sprites_list.draw(screen)

    #UNCOMMENT TO SEE THE DESIRED EFFECT
    #i= i+1
    #pygame.draw.arc(screen, (0,255,255),(25,25,450,450),0+(i*math.pi)/180,math.pi/6 +(i*math.pi)/180,10)
    pygame.display.flip() 
    clock.tick(60)

pygame.quit()

score 0 · Accepted Answer · answered Feb 19 '15 at 09:55

0

You draw the arc outside of the surface.

Here you pass the values 20 and 15 to Block:

block = Block(BLACK, 20, 15)

So you create a Surface with the size 20, 15:

self.image = pygame.Surface([width, height])

Then you draw the arc in the area 25,25,450,450:

pygame.draw.arc(self.image, (0,255,255),(25,25,450,450),0+(self.i*math.pi)/180,math.pi/6 +(self.i*math.pi)/180,10)

But that area is outside the surface, because it is only 20 pixels wide and 15 pixels high.

The area you passed to pygame.draw.arc is relative to self.image.

answered Feb 19 '15 at 09:55

sloth

99,095
21
171
219

One more thing, is it fine to write something like this in update() ? or it should be avoided ? `def update(self):` `self.i = self.i + 1` `self.image.fill(WHITE)` `self.image.set_colorkey(WHITE)` `pygame.draw.arc(self.image, (0,255,255),(0,0,450,450),0+(self.i*math.pi)/180,math.pi/6 +(self.i*math.pi)/180,10)` – ansrivas Feb 19 '15 at 12:55
@Sokio I think that's not a problem. If you have multiple `Block` objects and you observe a serious performance loss, it might be useful to cache the surfaces, but that's another topic. – sloth Feb 19 '15 at 13:04

Pygame's arc to be used as a sprite

1 Answers1