gistfile1.txt

import numpy as np
import math
from tkinter import *

tk=Tk()
WIDTH=5000
HEIGHT=4000
canvas=Canvas(tk,width=WIDTH,height=HEIGHT)
tk.title('mesh')
canvas.pack()

ITER=30000
LENGTH=50
DIMEN=50
ROWS=4
COLUMNS=4
SHEAR_MOD=50000
YOUNG_MOD=100
dt=.0005



def unit_vector(vector):
    return vector / np.linalg.norm(vector)

def perpendicular( a ) :
    b = np.empty_like(a)
    b[0] = -a[1]
    b[1] = a[0]
    return (b)

class Particles:
    def __init__(self,pos):
        self.shape=canvas.create_rectangle(DIMEN*pos[0],DIMEN*pos[1],DIMEN*pos[0]+10,DIMEN*pos[1]+10,fill='blue')
        self.pos=canvas.coords(self.shape)
        if x==0:
            self.vel=[0,200]
        else:
            self.vel=[0,0]

    def move(self,parts):
        for x in range(4):
            p1=parts[x]
            try:
                p2=parts[x+1]
            except:
                p2=parts[0]
            if p1=='none' or p2=='none':
                pass
            else:
                vec1=(p1.pos[0]-self.pos[0],p1.pos[1]-self.pos[1])
                vec2=(p2.pos[0]-self.pos[0],p2.pos[1]-self.pos[1])
                vec1_u = unit_vector(vec1)
                vec2_u = unit_vector(vec2)
                angle= np.arccos(np.clip(np.dot(vec1_u, vec2_u), -1.0, 1.0))
                torque=SHEAR_MOD*(angle-math.pi/2)
                perp1=-perpendicular(vec1_u)
                perp2=perpendicular(vec2_u)
                torque1=torque*np.array(perp1)
                torque2=torque*np.array(perp2)

                dist1=(self.pos[0]-p1.pos[0],self.pos[1]-p1.pos[1])
                force1=YOUNG_MOD*np.dot(((np.linalg.norm(dist1)-LENGTH)/np.linalg.norm(dist1)),(np.dot(dist1,(1,0)),np.dot(dist1,(0,1))))
                dist2=(self.pos[0]-p2.pos[0],self.pos[1]-p2.pos[1])
                force2=YOUNG_MOD*np.dot(((np.linalg.norm(dist2)-LENGTH)/np.linalg.norm(dist2)),(np.dot(dist2,(1,0)),np.dot(dist2,(0,1))))


                p1.vel+=(force1+torque1)*dt
                p2.vel+=(force2+torque2)*dt
                self.vel-=(force1+force2+torque1+torque2)*dt

                parts[x].vel=p1.vel
                try:
                    parts[x+1].vel=p2.vel
                except:
                    parts[0].vel=p2.vel

                canvas.move(p1.shape,p1.vel[0]*dt,p1.vel[1]*dt)
                canvas.move(p2.shape,p2.vel[0]*dt,p2.vel[1]*dt)
 
                canvas.move(self.shape,self.vel[0]*dt,self.vel[1]*dt)
                self.pos=canvas.coords(self.shape)
                p1.pos=canvas.coords(p1.shape)

                p2.pos=canvas.coords(p2.shape)




particles=[]
for x in range(COLUMNS):
    particles.append([])
    for y in range(ROWS):
        particles[x].append(Particles([x,y]))
        
for t in range(ITER):
    for column in range (COLUMNS):
        for particle in range (ROWS):
            if particle==0:
                partT='none'
            else:
                partT=particles[column][particle-1]
            if particle==ROWS-1:
                partB='none'
            else:
                partB=particles[column][particle+1]
            if column==0:
                partL='none'
            else:
                partL=particles[column-1][particle]
            if column==COLUMNS-1:
                partR='none'
            else:
                partR=particles[column+1][particle]
            pos=canvas.coords(particles[column][particle].shape)
            pos=[pos[0],pos[1]]
            particles[column][particle].move([partR,partT,partL,partB])

tk.mainloop()