init commit

README.md

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+# Double Pendulum In Processing.py
+
+Simple Port of the marvelous Daniel Shiffman from The Coding Train's double pendulum Processing sketch to Python.
+
+![Double Pendulum Animation](animation.webm)

double_pendulum.py

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+def setup():
+    size(900, 600)
+    global canvas, cx, cy
+    cx = width / 2
+    cy = 200
+    canvas = createGraphics(width, height)
+    canvas.beginDraw()
+    canvas.background(255)
+    canvas.endDraw()
+
+    global r1, r2, m1, m2, a1, a2, a1_v, a2_v, g, px2, py2
+    r1 = 200
+    r2 = 200
+    m1 = 40
+    m2 = 40
+    a1 = PI / 2
+    a2 = PI / 2
+    a1_v = 0
+    a2_v = 0
+    g = 1
+
+    px2 = -1
+    py2 = -1
+
+
+def draw():
+
+    background(255)
+    imageMode(CORNER)
+    image(canvas, 0, 0, width, height)
+    global r1, r2, m1, m2, a1, a2, a1_v, a2_v, g, px2, py2
+    num1 = -g * (2 * m1 + m2) * sin(a1)
+    num2 = -m2 * g * sin(a1 - 2 * a2)
+    num3 = -2 * sin(a1 - a2) * m2
+    num4 = a2_v * a2_v * r2 + a1_v * a1_v * r1 * cos(a1 - a2)
+    den = r1 * (2 * m1 + m2 - m2 * cos(2 * a1 - 2 * a2))
+    a1_a = (num1 + num2 + num3 * num4) / den
+
+    num1 = 2 * sin(a1 - a2)
+    num2 = a1_v * a1_v * r1 * (m1 + m2)
+    num3 = g * (m1 + m2) * cos(a1)
+    num4 = a2_v * a2_v * r2 * m2 * cos(a1 - a2)
+    den = r2 * (2 * m1 + m2 - m2 * cos(2 * a1 - 2 * a2))
+    a2_a = (num1 * (num2 + num3 + num4)) / den
+
+    translate(cx, cy)
+    stroke(0)
+    strokeWeight(2)
+
+    x1 = r1 * sin(a1)
+    y1 = r1 * cos(a1)
+
+    x2 = x1 + r2 * sin(a2)
+    y2 = y1 + r2 * cos(a2)
+
+    line(0, 0, x1, y1)
+    fill(0)
+    ellipse(x1, y1, m1, m1)
+
+    line(x1, y1, x2, y2)
+    fill(0)
+    ellipse(x2, y2, m2, m2)
+
+    a1_v += a1_a
+    a2_v += a2_a
+    a1 += a1_v
+    a2 += a2_v
+
+    canvas.beginDraw()
+    canvas.translate(cx, cy)
+    canvas.stroke(0)
+
+    if frameCount > 1:
+        canvas.line(px2, py2, x2, y2)
+
+    canvas.endDraw()
+
+    px2 = x2
+    py2 = y2
+

double_pendulum.pyde

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+
+def setup():
+    size(900, 600)
+    global canvas, cx, cy
+    cx = width / 2
+    cy = 200
+    canvas = createGraphics(width, height)
+    canvas.beginDraw()
+    canvas.background(255)
+    canvas.endDraw()
+    global r1, r2, m1, m2, a1, a2, a1_v, a2_v, g, px2, py2
+    r1 = 200
+    r2 = 200
+    m1 = 40
+    m2 = 40
+    a1 = PI / 2
+    a2 = PI / 2
+    a1_v = 0
+    a2_v = 0
+    g = 1
+
+    px2 = -1
+    py2 = -1
+
+def draw():
+
+    background(255)
+    imageMode(CORNER)
+    image(canvas, 0, 0, width, height)
+    global r1, r2, m1, m2, a1, a2, a1_v, a2_v, g, px2, py2
+    num1 = -g * (2 * m1 + m2) * sin(a1)
+    num2 = -m2 * g * sin(a1 - 2 * a2)
+    num3 = -2 * sin(a1 - a2) * m2
+    num4 = a2_v * a2_v * r2 + a1_v * a1_v * r1 * cos(a1 - a2)
+    den = r1 * (2 * m1 + m2 - m2 * cos(2 * a1 - 2 * a2))
+    a1_a = (num1 + num2 + num3 * num4) / den
+
+    num1 = 2 * sin(a1 - a2)
+    num2 = a1_v * a1_v * r1 * (m1 + m2)
+    num3 = g * (m1 + m2) * cos(a1)
+    num4 = a2_v * a2_v * r2 * m2 * cos(a1 - a2)
+    den = r2 * (2 * m1 + m2 - m2 * cos(2 * a1 - 2 * a2))
+    a2_a = (num1 * (num2 + num3 + num4)) / den
+
+    translate(cx, cy)
+    stroke(0)
+    strokeWeight(2)
+
+    x1 = r1 * sin(a1)
+    y1 = r1 * cos(a1)
+
+    x2 = x1 + r2 * sin(a2)
+    y2 = y1 + r2 * cos(a2)
+
+    line(0, 0, x1, y1)
+    fill(0)
+    ellipse(x1, y1, m1, m1)
+
+    line(x1, y1, x2, y2)
+    fill(0)
+    ellipse(x2, y2, m2, m2)
+
+    a1_v += a1_a
+    a2_v += a2_a
+    a1 += a1_v
+    a2 += a2_v
+
+    canvas.beginDraw()
+    canvas.translate(cx, cy)
+    canvas.stroke(0)
+
+    if frameCount > 1:
+        canvas.line(px2, py2, x2, y2)
+
+    canvas.endDraw()
+
+    px2 = x2
+    py2 = y2

doublependulum.pde

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+// Daniel Shiffman
+// http://codingtra.in
+// http://patreon.com/codingtrain
+
+// Double Pendulum
+// https://youtu.be/uWzPe_S-RVE
+
+float r1 = 200; // length of first pendulum
+float r2 = 200; // length of second pendulum
+float m1 = 40; //  mass of first pendulum excluding weight of string
+float m2 = 40; // mass of second pendulum excluding weight of string
+float a1 = PI/2; // angle formed by first pendulum and normal - angle1
+float a2 = PI/2; //angle formed by second pendulum and normal - angle2
+float a1_v = 0; //angular velocity of pendulum1
+float a2_v = 0; //angular velocity of pendulum2
+float g = 1; //gravitational constant (realistic value not considered for simplicity )
+
+float px2 = -1; // previous position of second pendulum sphere - x offset
+float py2 = -1; // previos position of second pendulum sphere - y offset
+float cx, cy; //centre of x and y for background
+
+PGraphics canvas; // canvas is just a variable name DO NOT CONFUSE IT WITH P5.JS
+
+void setup() {
+  size(900, 600); 
+  cx = width/2;
+  cy = 200;
+  canvas = createGraphics(width, height);
+  canvas.beginDraw();
+  canvas.background(255);
+  canvas.endDraw();
+}
+
+void draw() {
+  background(255);
+  imageMode(CORNER);
+  image(canvas, 0, 0, width, height);
+  // numerators are moduled 
+  float num1 = -g * (2 * m1 + m2) * sin(a1);
+  float num2 = -m2 * g * sin(a1-2*a2);
+  float num3 = -2*sin(a1-a2)*m2;
+  float num4 = a2_v*a2_v*r2+a1_v*a1_v*r1*cos(a1-a2);
+  float den = r1 * (2*m1+m2-m2*cos(2*a1-2*a2));
+  float a1_a = (num1 + num2 + num3*num4) / den;
+
+  num1 = 2 * sin(a1-a2);
+  num2 = (a1_v*a1_v*r1*(m1+m2));
+  num3 = g * (m1 + m2) * cos(a1);
+  num4 = a2_v*a2_v*r2*m2*cos(a1-a2);
+  den = r2 * (2*m1+m2-m2*cos(2*a1-2*a2));
+  float a2_a = (num1*(num2+num3+num4)) / den;
+
+  translate(cx, cy);
+  stroke(0);
+  strokeWeight(2);
+
+  float x1 = r1 * sin(a1);
+  float y1 = r1 * cos(a1);
+
+  float x2 = x1 + r2 * sin(a2);
+  float y2 = y1 + r2 * cos(a2);
+
+
+  line(0, 0, x1, y1);
+  fill(0);
+  ellipse(x1, y1, m1, m1);
+
+  line(x1, y1, x2, y2);
+  fill(0);
+  ellipse(x2, y2, m2, m2);
+
+  a1_v += a1_a;
+  a2_v += a2_a;
+  a1 += a1_v;
+  a2 += a2_v;
+  // as momentum increases  , slowly pendulum comes to rest
+  // a1_v *= 0.99; // for drag
+  // a2_v *= 0.99; // for drag
+
+  canvas.beginDraw();
+  //canvas.background(0, 1);
+  canvas.translate(cx, cy);
+  canvas.stroke(0);
+  if (frameCount > 1) {
+    canvas.line(px2, py2, x2, y2);
+  }
+  canvas.endDraw();
+
+
+  px2 = x2;
+  py2 = y2;
+}

sketch.properties

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+mode=Python
+mode.id=jycessing.mode.PythonMode