Creating curvature animation in python

Question

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.

1) Create simple model of chasing 2) Choose graphic library for representation 3) Implement. What step cause problems? — MBo, Jan 21 '20 at 08:09
Thanks for the answer. The second step looks a bit difficult for me because I can not find the specific library which can be associated with graphic showcase of 2d cartesian plane and two points interacting with each other — Luka Khachidze, Jan 21 '20 at 08:19
Maybe that's more algorithmic than a Python question. Stack Overflow is more language/framework related. — Abdur-Rahmaan Janhangeer, Jan 21 '20 at 08:20
it seems like "enemy following player" and it was ask in last week for `tkinter` and `pygame` — furas, Jan 21 '20 at 08:51

furas · Accepted Answer · 2020-01-21T09:28:25.530

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

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.

Creating curvature animation in python

1 Answers1