how to make rotate polygon on key in pygame? - pygame

Question

I am trying to make my polygon rotate able. But when I input new_point the report is new_point aren't define. This is giving me a headache
def xoay_hinh(key):
lx, ly = zip(*hinh)
min_x, min_y, max_x, max_y = min(lx), min(ly), max(lx), max(ly)
new_hinh = hinh
if key[pygame.K_r]:
cx = ((max_x - min_x)/2) + min_x
cy = ((max_y - min_y)/2) + min_y
for point in hinh and for new_point in new_hinh :
new_point[0] = cy - point[1]
new_point[1] = cy + point[0] - cx
point[0] = new_point[0]
point[1] = new_point[1]
T had try to used pygame.tranfrom.rotate() and replace "new_point" with different value but the program still refuse to run

Answer 1

There is no need to create a pygame.Surface and to use pygame.transform.rotate to rotate the points of a polygon. You can use pygame.math.Vectore2.rotate tor create a rotated list of points.
define the pivot point (e.g. center of the polygon)
calculate the vectors from the pivot point to the points of the polygon
use pygame.math.Vectore2.rotate to rotate the vectors
add the pivot point to the rotated vectors
def rotate_points_around_pivot(points, pivot, angle):
pp = pygame.math.Vector2(pivot)
rotated_points = [
(pygame.math.Vector2(x, y) - pp).rotate(angle) + pp for x, y in points]
return rotated_points
Minimal example:
import pygame
def rotate_points_around_pivot(points, pivot, angle):
pp = pygame.math.Vector2(pivot)
rotated_points = [
(pygame.math.Vector2(x, y) - pp).rotate(angle) + pp for x, y in points]
return rotated_points
def draw_rotated_polygon(surface, color, points, angle, pivot=None):
if pivot == None:
lx, ly = zip(*points)
min_x, min_y, max_x, max_y = min(lx), min(ly), max(lx), max(ly)
bounding_rect = pygame.Rect(min_x, min_y, max_x - min_x, max_y - min_y)
pivot = bounding_rect.center
rotated_points = rotate_points_around_pivot(points, pivot, angle)
pygame.draw.polygon(surface, color, rotated_points)
pygame.init()
window = pygame.display.set_mode((250, 250))
clock = pygame.time.Clock()
pivot = (125, 125)
size = 90
points = [(0, -1), (-0.8660, 0.5), (0.8660, 0.5)]
points = [(pivot[0] + x * size, pivot[1] + y * size) for x, y in points]
angle = 0
run = True
while run:
clock.tick(60)
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
key = pygame.key.get_pressed()
if key[pygame.K_r]:
angle += 1
window.fill("black")
draw_rotated_polygon(window, "white", points, angle, pivot)
pygame.display.flip()
pygame.quit()