Animate a point over a list of bezier curves

bezier_animation.py

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()