Easing Example 1#

Easing Example

Source#

easing_example.py#
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"""
Example showing how to use the easing functions for position.

See:
https://easings.net/
...for a great guide on the theory behind how easings can work.

See example 2 for how to use easings for angles.

If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.easing_example_1
"""
import arcade

SPRITE_SCALING = 0.5

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
SCREEN_TITLE = "Easing Example"

BACKGROUND_COLOR = "#F5D167"
TEXT_COLOR = "#4B1DF2"
BALL_COLOR = "#42B5EB"
LINE_COLOR = "#45E6D0"
LINE_WIDTH = 3

X_START = 40
X_END = 760
Y_INTERVAL = 50
BALL_RADIUS = 13
TIME = 3.0


class EasingCircle(arcade.SpriteCircle):
    """ Player class """

    def __init__(self, radius, color):
        """ Set up the player """

        # Call the parent init
        super().__init__(radius, color)

        self.easing_x_data = None
        self.easing_y_data = None

    def on_update(self, delta_time: float = 1 / 60):
        if self.easing_x_data is not None:
            done, self.center_x = arcade.ease_update(self.easing_x_data, delta_time)
            if done:
                x = X_START
                if self.center_x < SCREEN_WIDTH / 2:
                    x = X_END
                ex, ey = arcade.ease_position(self.position,
                                              (x, self.center_y),
                                              rate=180,
                                              ease_function=self.easing_x_data.ease_function)
                self.easing_x_data = ex

        if self.easing_y_data is not None:
            done, self.center_y = arcade.ease_update(self.easing_y_data, delta_time)
            if done:
                self.easing_y_data = None


class MyGame(arcade.Window):
    """ Main application class. """

    def __init__(self, width, height, title):
        """ Initializer """

        # Call the parent class initializer
        super().__init__(width, height, title)

        # Set the background color
        self.background_color = arcade.color_from_hex_string(BACKGROUND_COLOR)

        self.ball_list = None
        self.text_list = []
        self.lines = None

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.ball_list = arcade.SpriteList()
        self.lines = arcade.ShapeElementList()

        def create_ball(ball_y, ease_function):
            ball = EasingCircle(BALL_RADIUS, arcade.color_from_hex_string(BALL_COLOR))
            ball.position = X_START, ball_y
            p1 = ball.position
            p2 = (X_END, ball_y)
            ex, ey = arcade.ease_position(p1, p2, time=TIME, ease_function=ease_function)
            ball.ease_function = ease_function
            ball.easing_x_data = ex
            ball.easing_y_data = ey
            return ball

        def create_line(line_y):
            line = arcade.create_line(X_START, line_y - BALL_RADIUS - LINE_WIDTH,
                                      X_END, line_y - BALL_RADIUS,
                                      line_color, line_width=LINE_WIDTH)
            return line

        def create_text(text_string):
            text = arcade.Text(text_string, X_START, y - BALL_RADIUS, color=text_color, font_size=14)
            return text

        def add_item(item_y, ease_function, text):
            ball = create_ball(item_y, ease_function)
            self.ball_list.append(ball)
            text = create_text(text)
            self.text_list.append(text)
            line = create_line(item_y)
            self.lines.append(line)

        text_color = arcade.color_from_hex_string(TEXT_COLOR)
        line_color = arcade.color_from_hex_string(LINE_COLOR)

        y = Y_INTERVAL
        add_item(y, arcade.linear, "Linear")

        y += Y_INTERVAL
        add_item(y, arcade.ease_out, "Ease out")

        y += Y_INTERVAL
        add_item(y, arcade.ease_in, "Ease in")

        y += Y_INTERVAL
        add_item(y, arcade.smoothstep, "Smoothstep")

        y += Y_INTERVAL
        add_item(y, arcade.ease_in_out, "Ease in/out")

        y += Y_INTERVAL
        add_item(y, arcade.ease_out_elastic, "Ease out elastic")

        y += Y_INTERVAL
        add_item(y, arcade.ease_in_back, "Ease in back")

        y += Y_INTERVAL
        add_item(y, arcade.ease_out_back, "Ease out back")

        y += Y_INTERVAL
        add_item(y, arcade.ease_in_sin, "Ease in sin")

        y += Y_INTERVAL
        add_item(y, arcade.ease_out_sin, "Ease out sin")

        y += Y_INTERVAL
        add_item(y, arcade.ease_in_out_sin, "Ease in out sin")

    def on_draw(self):
        """ Render the screen. """

        # This command has to happen before we start drawing
        self.clear()

        self.lines.draw()

        # Draw all the sprites.
        self.ball_list.draw()

        for text in self.text_list:
            text.draw()

    def on_update(self, delta_time):
        """ Movement and game logic """

        # Call update on all sprites (The sprites don't do much in this
        # example though.)
        self.ball_list.on_update(delta_time)


def main():
    """ Main function """
    window = MyGame(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()