Pendulum: Create a class for regular polygon

Pendulum/Pendulum.js

@@ -1,26 +1,120 @@
 // RotatingTranslatedTriangle.js (c) 2012 matsuda
+"use strict"
 
 const vertex_shader = `
   attribute vec4 a_Position;
   uniform mat4 u_ModelMatrix;
-  
-  void main() 
+
+  void main()
   {
     gl_Position = u_ModelMatrix * a_Position;
   }	`;
 
 
 const fragment_shader = `
-  void main() 
+  void main()
   {
     gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
   }	`;
 
+// Point size of the anchor
+var POINT_SIZE = 5;
+// Radius of the bob
+var BOB_RADIUS = 0.1;
+// length of the wire
+var PEN_LENGTH = 0.8;
 // Rotation angle (degrees/second)
-var ANGLE_STEP = 45.0;
+var A_VELOCITY = 45.0;
 
-function main() 
-{
+// Classes
+//   homo2: Stores a 2d vector or point in homog. coords
+class homog2 {
+  constructor(x = 0, y = 0, w = 0) {
+    this.x = x;
+    this.y = y;
+    this.w = w;
+  }
+  // Add with modify
+  add_m(rhs) {
+    if (rhs) {
+      this.x += rhs.x;
+      this.y += rhs.y;
+      this.w += rhs.w;
+      return this;
+    }
+    else return null;
+  }
+  // scalar multiply with modify
+  smul_m(scalar) {
+    if (typeof(rhs) === "number") {
+      this.x *= rhs;
+      this.y *= rhs;
+      this.w *= rhs;
+      return this;
+    }
+    else return null;
+  }
+  // copy
+  copy() {
+    return new homog2(this.x, this.y, this.w);
+  }
+  // create vector/point from 2d polar coordinates
+  from_polar(r = 0, theta = 0, w = 0) {
+    this.x = r * Math.cos(theta);
+    this.y = r * Math.sin(theta);
+    this.w = w;
+    return this;
+  }
+}
+
+// hexagon2 class: Holds 6 vertices and a center point. Only constructs perfect hexagons.
+class hexagon2 {
+  // constructor: Make a new regular polygon
+  constructor({sides = 6, radius = 0, rotation = 0, center = { x: 0, y: 0 } } = {}) {
+    // lenth is center + sides
+    this.length = 1;
+    this.center = new homog2(center.x, center.y, 1);
+    this.v = [];
+    for (var i = 0; i <= sides; i++) {
+      this.v[i] = new homog2().from_polar(radius, rotation + (i*2*Math.PI / sides)).add_m(this.center);
+      this.length++;
+    }
+  }
+  // Convert to Float32Array [center, v0, v1, ...]
+  to_array() {
+    // allocate space for center.xy + vertices.xy
+    var ret = new Float32Array((1 + this.v.length) * 2);
+    // save the center
+    ret[0] = this.center.x;
+    ret[1] = this.center.y;
+    // save the vertices
+    for (var i = 0; i < this.v.length; i++) {
+      var j = 2 * (i + 1);
+      ret[j]   = this.v[i].x;
+      ret[j+1] = this.v[i].y;
+    }
+    return ret;
+  }
+  draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix) {
+    // Set the rotation matrix
+    modelMatrix.setRotate(currentAngle, 0, 0, 1);
+    // Pass the rotation matrix to the vertex shader
+    gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements);
+    // Clear <canvas>
+    gl.clear(gl.COLOR_BUFFER_BIT);
+    // Draw the pendulum
+    gl.drawArrays(gl.TRIANGLE_FAN, 0, n);
+  }
+}
+
+class pendulum2 {
+  constructor({angle = 0, length = PEN_LENGTH, radius = BOB_RADIUS} = {}) {
+    this.bob = new hexagon2({radius: radius, center: {x: 0, y: -length}});
+    console.log(this);
+  }
+}
+
+function main() {
   // Retrieve <canvas> element
   var canvas = document.getElementById('webgl');
 
@@ -32,16 +126,17 @@ function main()
   }
 
   // Initialize shaders
-  if (!initShaders(gl, vertex_shader, fragment_shader))
-  {
+  if (!initShaders(gl, vertex_shader, fragment_shader)) {
     console.log('Failed to intialize shaders.');
     return;
   }
 
+  // create a pendulum object
+  var pendulum = new pendulum2({angle: 0, length: 0});
+
   // Write the positions of vertices to a vertex shader
-  var n = initVertexBuffers(gl);
-  if (n < 0) 
-  {
+  var n = initVertexBuffers(gl, pendulum);
+  if (n < 0) {
     console.log('Failed to set the positions of the vertices');
     return;
   }
@@ -51,53 +146,50 @@ function main()
 
   // Get storage location of u_ModelMatrix
   var u_ModelMatrix = gl.getUniformLocation(gl.program, 'u_ModelMatrix');
-  if (!u_ModelMatrix) 
-  { 
+  if (!u_ModelMatrix) {
     console.log('Failed to get the storage location of u_ModelMatrix');
     return;
   }
 
   // Current rotation angle
   var currentAngle = 0.0;
-  
+
   // Model matrix
   var modelMatrix = new Matrix4();
 
   // Start drawing
-  var tick = function() 
-  {
+  var tick = function () {
     currentAngle = animate(currentAngle);  // Update the rotation angle
-    draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix);   // Draw the triangle
+    pendulum.bob.draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix);   // Draw the triangle
     requestAnimationFrame(tick, canvas);   // Request that the browser ?calls tick
   };
   tick();
 }
 
-function initVertexBuffers(gl) 
-{
-  var vertices = new Float32Array ([
-    0, 0.5,   -0.5, -0.5,   0.5, -0.5
-  ]);
-  var n = 3;   // The number of vertices
+function initVertexBuffers(gl, pendulum) {
+  // var vertices = new Float32Array([
+  //   0, 0.5, -0.5, -0.5, 0.5, -0.5
+  // ]);
+  // var n = 3;   // The number of vertices
+  var vertices = pendulum.bob.to_array();
+  var n = pendulum.bob.length;
 
   // Create a buffer object
   var vertexBuffer = gl.createBuffer();
-  if (!vertexBuffer) 
-  {
+  if (!vertexBuffer) {
     console.log('Failed to create the buffer object');
     return -1;
   }
 
   // Bind the buffer object to target
   gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
-  
+
   // Write date into the buffer object
   gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
 
   // Assign the buffer object to a_Position variable
   var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
-  if(a_Position < 0) 
-  {
+  if (a_Position < 0) {
     console.log('Failed to get the storage location of a_Position');
     return -1;
   }
@@ -109,12 +201,11 @@ function initVertexBuffers(gl)
   return n;
 }
 
-function draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix) 
-{
+function draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix) {
   // Set the rotation matrix
   modelMatrix.setRotate(currentAngle, 0, 0, 1);
   modelMatrix.translate(0.35, 0, 0);
- 
+
   // Pass the rotation matrix to the vertex shader
   gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements);
 
@@ -127,23 +218,20 @@ function draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix)
 
 // Last time that this function was called
 var g_last = Date.now();
-function animate(angle) 
-{
+function animate(angle) {
   // Calculate the elapsed time
   var now = Date.now();
   var elapsed = now - g_last;
   g_last = now;
   // Update the current rotation angle (adjusted by the elapsed time)
-  var newAngle = angle + (ANGLE_STEP * elapsed) / 1000.0;
+  var newAngle = angle + (A_VELOCITY * elapsed) / 1000.0;
   return newAngle %= 360;
 }
 
-function up() 
-{
-  ANGLE_STEP += 10; 
+function up() {
+  A_VELOCITY += 10;
 }
 
-function down() 
-{
-  ANGLE_STEP -= 10; 
+function down() {
+  A_VELOCITY -= 10;
 }