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pythonmathmotion

Creating curvature animation in python

I am facing one problem for 2 weeks now and I still cannot figure it out even from where to start. The problem is about creating a curvature animation which is about two points chasing each other. one of them moves on a straight line on the x-axis and the other one starts from down from the x-axis(on y-axis e.g p(0:-10)) and by the principle of chasing, the second one tries to catch the first one while facing it continuously. I wrote some code that helped me to get actual answers but I am not able to visualize it in a very precious way. I am using python as my main coding language.

Thank you in advance Luka K.

Solution

  • It seems like enemy following player which was asked last week for tkinter and pygame

    enter image description here

    You calculate vector between objects

    diff_x = player_x - enemy_x
diff_y = player_y - enemy_y

    and distance

    distance = (diff_x**2 + diff_y**2)**0.5  # Pythagoras: a**2 + b**2 = c**2

    to calculate normalized vector (vector which has length 1)

    normal_x = diff_x/distance
normal_y = diff_y/distance

    which you can multiply by speed to calculate move_x and move_y for enemy

    enemy_move_x = enemy_speed * normal_x
enemy_move_y = enemy_speed * normal_y

    and you can use it to move enemy and to draw line.

    To draw it you can use different modules - any GUI framework like tkinter, PyQt, wxPython or game/media library like pygame or pyglet. Eventually you could generate images which you could use to create animated GIF.

    import tkinter as tk

def follow(player_x, player_y, enemy_x, enemy_y, enemy_speed=5):
    diff_x = player_x - enemy_x
    diff_y = player_y - enemy_y

    distance = (diff_x**2 + diff_y**2)**0.5  # Pythagoras: a**2 + b**2 = c**2

    if distance <= enemy_speed:
        return diff_x, diff_y

    normal_x = diff_x/distance
    normal_y = diff_y/distance

    enemy_move_x = enemy_speed * normal_x
    enemy_move_y = enemy_speed * normal_y

    return enemy_move_x, enemy_move_y

def update_game():
    global player_x
    global player_y
    global enemy_x
    global enemy_y

    # draw line for player
    canvas.create_line(player_x, player_y, player_x+player_move_x, player_y+player_move_y, fill='green')

    # move player
    player_x += player_move_x
    player_y += player_move_y
    canvas.move(player_id, player_move_x, player_move_y)

    # calculate move for enemy
    enemy_move_x, enemy_move_y = follow(player_x, player_y, enemy_x, enemy_y, enemy_speed)

    # draw line for enemy
    canvas.create_line(enemy_x, enemy_y, enemy_x+enemy_move_x, enemy_y+enemy_move_y, fill='red')

    # move enemy
    enemy_x += enemy_move_x
    enemy_y += enemy_move_y
    canvas.move(enemy_id, enemy_move_x, enemy_move_y)

    root.after(100, update_game) # repeate after 100ms (0.1s)

# --- main ---

# player start position and move ("speed")
player_x = 5
player_y = 50
player_move_x = 4
player_move_y = 0 # try for `1`

# enemy start position and speed
enemy_x = 5
enemy_y = 500
enemy_speed = 5

root = tk.Tk()

canvas = tk.Canvas(root, width=750, height=500)#, bg='gray')
canvas.pack()

player_id = canvas.create_oval(player_x-5, player_y-5, player_x+5, player_y+5, fill='green')
enemy_id = canvas.create_oval(enemy_x-5, enemy_y-5, enemy_x+5, enemy_y+5, fill='red')

update_game()

root.mainloop()

    BTW: in answer to question How to make enemy follow player you have the same code but you have to move player using keys WASD and it doesn't draw line.