Created
December 22, 2023 10:03
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Animate a point over a list of bezier curves
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import bezier | |
import pygame | |
class BezierLoop: | |
WIDTH = 400 | |
HEIGHT = 400 | |
def prepare_window(self): | |
self.screen = pygame.display.set_mode((self.WIDTH, self.HEIGHT)) | |
self.screen.fill((0, 0, 0)) | |
def make_curves(self): | |
ret = [] | |
ret.append(bezier.Curve.from_nodes([ | |
[100, 100], | |
[100, 110], | |
])) | |
ret.append(bezier.Curve.from_nodes([ | |
[100, 100, 200], | |
[110, 300, 300], | |
])) | |
ret.append(bezier.Curve.from_nodes([ | |
[200, 300], | |
[300, 300], | |
])) | |
ret.append(bezier.Curve.from_nodes([ | |
[300, 300, 100, 100], | |
[300, 100, 200, 100], | |
])) | |
return ret | |
def animate_point_as_single_curve(self, curves, idx): | |
whole_len = 100 * len(curves) | |
n_idx = whole_len * idx // 100 | |
curve_idx = n_idx // 100 | |
c = curves[curve_idx] | |
n_idx = n_idx % 100 | |
if n_idx > 100: | |
n_idx = 100 | |
v = c.evaluate(n_idx / 100) | |
v = (v[0][0], v[1][0]) | |
pygame.draw.circle(self.screen, (0, 255, 0), v, 6) | |
def animate_smooth(self, curves, idx): | |
len_all = 0 | |
for c in curves: | |
len_all += c.length | |
projected_idx = len_all * idx / 100 | |
previous_len = 0 | |
current_len = 0 | |
for c in curves: | |
current_len += c.length | |
if projected_idx < current_len: | |
partial = projected_idx - previous_len | |
v = c.evaluate(partial / c.length) | |
v = (v[0][0], v[1][0]) | |
pygame.draw.circle(self.screen, (255, 0, 0), v, 6) | |
break | |
previous_len = current_len | |
def animate_point_each_curve(self, curves, idx): | |
for c in curves: | |
v = c.evaluate(idx / 100) | |
v = (v[0][0], v[1][0]) | |
pygame.draw.circle(self.screen, (0, 0, 255), v, 6) | |
def draw_curves(self, curves): | |
# each letter: | |
for c in curves: | |
last_pt = None | |
for i in range(21): | |
v = c.evaluate(i / 20) | |
v = (v[0][0], v[1][0]) | |
if not last_pt is None: | |
pygame.draw.line(self.screen, (255, 0, 255), last_pt, v) | |
last_pt = v | |
def run(self): | |
dt = 1 | |
clock = pygame.time.Clock() | |
do_run = True | |
curves = self.make_curves() | |
cnt = -50 | |
idx = -1 | |
w_idx = -1 | |
while do_run: | |
for event in pygame.event.get(): | |
if event.type == pygame.QUIT: | |
do_run = False | |
break | |
self.screen.fill((0, 0, 0)) | |
self.draw_curves(curves) | |
idx = (idx + 1) % 100 | |
self.animate_point_each_curve(curves, idx) | |
self.animate_point_as_single_curve(curves, idx) | |
self.animate_smooth(curves, idx) | |
pygame.display.flip() | |
dt = clock.tick(60) | |
if "__main__" == __name__: | |
pygame.init() | |
pgm = BezierLoop() | |
pgm.prepare_window() | |
pgm.run() | |
pygame.quit() |
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