Weird angles, Pygame

Question

I was messing around with pygame and tried to make a line spin around its starting point, the problem is that for some reason I have to use negative degrees to make them work in an expected way, otherwise it seems like there's a "delay".

Here's the code:

import pygame
import time
import math
import sys


CLOCK = pygame.time.Clock()

POSITION_WINDOWS_X = 360
POSITION_WINDOWS_Y = 140
WINDOW_SIZE = (400, 400)
SCREEN = pygame.display.set_mode((WINDOW_SIZE))

HALF_SCREEN = [(i)//2 for i in WINDOW_SIZE]
DISPLAY = pygame.Surface(HALF_SCREEN)



ANGLE = math.radians(135)
LENGTH = 50

while True:

    DISPLAY.fill((146,244,255))

    pygame.draw.line(
        DISPLAY,
        (255, 0, 0),
        [100, 100],
        [
            100 + LENGTH * math.cos(ANGLE), 
            100 + LENGTH * math.sin(ANGLE)
        ],
        5
    )    

    ANGLE -= math.radians(1)
    ANGLE %= -math.pi*2

    print(round(math.degrees(ANGLE)), 'degrees')

    for event in pygame.event.get():
        
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    SCREEN.blit(pygame.transform.scale(DISPLAY, WINDOW_SIZE), (0, 0))

    pygame.display.update()
    CLOCK.tick(60)

Keep in mind that x is horizontal as usual, and +y is down in image coordinates. — Mad Physicist, Mar 05 '21 at 00:43
@MadPhysicist Oh you are right, that went over my head, thanks. — qwerty_url, Mar 05 '21 at 01:00
Glad it helped. The angles aren't backwards. Just a different coordinate system. Don't know about the delay though. — Mad Physicist, Mar 05 '21 at 01:08

Frank · Answer 1 · 2021-03-05T00:43:25.493

According to your description, I modified the code, and check the result (Both positive and negative), there is no delay.

For the code. Try this:

Negative

import pygame
import time
import math
import sys

CLOCK = pygame.time.Clock()

POSITION_WINDOWS_X = 360
POSITION_WINDOWS_Y = 140
WINDOW_SIZE = (400, 400)
SCREEN = pygame.display.set_mode((WINDOW_SIZE))

HALF_SCREEN = [(i) // 2 for i in WINDOW_SIZE]
DISPLAY = pygame.Surface(HALF_SCREEN)

ANGLE = math.radians(0)
LENGTH = 50

while True:

    DISPLAY.fill((146, 244, 255))

    pygame.draw.line(
        DISPLAY,
        (255, 0, 0),
        [100, 100],
        [
            100 + LENGTH * math.cos(ANGLE),
            100 + LENGTH * math.sin(ANGLE)
        ],
        5
    )

    ANGLE -= math.radians(1)
    ANGLE %= math.pi * 2

    print(round(math.degrees(ANGLE)), 'degrees')

    for event in pygame.event.get():

        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    SCREEN.blit(pygame.transform.scale(DISPLAY, WINDOW_SIZE), (0, 0))

    pygame.display.update()
    CLOCK.tick(60)

Positive

import pygame
import time
import math
import sys

CLOCK = pygame.time.Clock()

POSITION_WINDOWS_X = 360
POSITION_WINDOWS_Y = 140
WINDOW_SIZE = (400, 400)
SCREEN = pygame.display.set_mode((WINDOW_SIZE))

HALF_SCREEN = [(i) // 2 for i in WINDOW_SIZE]
DISPLAY = pygame.Surface(HALF_SCREEN)

ANGLE = math.radians(0)
LENGTH = 50

while True:

    DISPLAY.fill((146, 244, 255))

    pygame.draw.line(
        DISPLAY,
        (255, 0, 0),
        [100, 100],
        [
            100 + LENGTH * math.cos(ANGLE),
            100 + LENGTH * math.sin(ANGLE)
        ],
        5
    )

    ANGLE += math.radians(1)
    ANGLE %= math.pi * 2

    print(round(math.degrees(ANGLE)), 'degrees')

    for event in pygame.event.get():

        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    SCREEN.blit(pygame.transform.scale(DISPLAY, WINDOW_SIZE), (0, 0))

    pygame.display.update()
    CLOCK.tick(60)

Here is the print:

1 degrees
2 degrees
3 degrees
4 degrees
5 degrees
6 degrees
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Weird angles, Pygame

1 Answers1