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HTML 

              
                <!DOCTYPE HTML>
<html>

<script id="vertex-shader" type="x-shader/x-vertex">
attribute  vec4 vPosition;
attribute  vec4 vColor;
varying vec4 fColor;

uniform mat4 modelViewMatrix;
uniform mat4 projectionMatrix;

void main() 
{
    fColor = vColor;
    gl_Position = projectionMatrix * modelViewMatrix * vPosition;
} 
</script>

<script id="fragment-shader" type="x-shader/x-fragment">

precision mediump float;

varying  vec4 fColor;

void main() 
{ 
    gl_FragColor = fColor;
} 
</script>

<script type="text/javascript" src="https://www.cs.unm.edu/~angel/WebGL/7E/Common/webgl-utils.js"></script>
<script type="text/javascript" src="https://www.cs.unm.edu/~angel/WebGL/7E/Common/initShaders.js"></script>
<script type="text/javascript" src="https://www.cs.unm.edu/~angel/WebGL/7E/Common/MV.js"></script>

<body>
<canvas id="gl-canvas" width="512" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
  
  <table>
    <tr>
      <td>Base rotation</td>
      <td><button id = "Button1">Decrease</button></td>
      <td><span id="base"></span></td>
      <td><button id = "Button2">Increase</button></td>
    </tr>
    <tr>
      <td>Lower arm angle</td>
      <td><button id = "Button3">Decrease</button></td>
      <td><span id="lower"></span></td>
      <td><button id = "Button4">Increase</button></td>
    </tr>
    <tr>
      <td>Upper arm angle</td>
      <td><button id = "Button5">Decrease</button></td>
      <td><span id="upper"></span></td>
      <td><button id = "Button6">Increase</button></td>
    </tr>
    <tr>
      <td><button id = "Button7">Reset</button></td>
    </tr>
  </table>
  
</body>
</html>
!

CSS
!

JS 

              
                var eye = vec3(10.0, 10.0, 10.0);
var at = vec3(0.0, 5.0, 0.0);
var up = vec3(0.0, 1.0, 0.0);

var fovy = 60;
var aspect;
var near = 0.1;
var far = 1000;


var NumVertices = 36; //(6 faces)(2 triangles/face)(3 vertices/triangle)

var points = [];
var colors = [];

var vertices = [
    vec4( -0.5, -0.5,  0.5, 1.0 ),
    vec4( -0.5,  0.5,  0.5, 1.0 ),
    vec4(  0.5,  0.5,  0.5, 1.0 ),
    vec4(  0.5, -0.5,  0.5, 1.0 ),
    vec4( -0.5, -0.5, -0.5, 1.0 ),
    vec4( -0.5,  0.5, -0.5, 1.0 ),
    vec4(  0.5,  0.5, -0.5, 1.0 ),
    vec4(  0.5, -0.5, -0.5, 1.0 )
];

// RGBA colors
var vertexColors = [
    vec4( 1.0, 1.0, 1.0, 1.0 ),  // white
    vec4( 1.0, 0.0, 0.0, 1.0 ),  // red
    vec4( 1.0, 1.0, 0.0, 1.0 ),  // yellow
    vec4( 0.0, 1.0, 0.0, 1.0 ),  // green
    vec4( 0.0, 0.0, 1.0, 1.0 ),  // blue
    vec4( 1.0, 0.0, 1.0, 1.0 ),  // magenta
    vec4( 0.0, 0.0, 0.0, 1.0 ),  // black
    vec4( 0.0, 1.0, 1.0, 1.0 )   // cyan
];


// Parameters controlling the size of the Robot's arm

var BASE_HEIGHT      = 2.0;
var BASE_WIDTH       = 5.0;
var LOWER_ARM_HEIGHT = 5.0;
var LOWER_ARM_WIDTH  = 0.5;
var UPPER_ARM_HEIGHT = 5.0;
var UPPER_ARM_WIDTH  = 0.5;

// Shader transformation matrices

var modelViewMatrix, projectionMatrix;

// Array of rotation angles (in degrees) for each rotation axis

var Base = 0;
var LowerArm = 1;
var UpperArm = 2;


var theta= [ 0, 0, 0];

var angle = 0;

var modelViewMatrixLoc;

var vBuffer, cBuffer;

//----------------------------------------------------------------------------

function quad(  a,  b,  c,  d ) {
    colors.push(vertexColors[a]); 
    points.push(vertices[a]); 
    colors.push(vertexColors[a]); 
    points.push(vertices[b]); 
    colors.push(vertexColors[a]); 
    points.push(vertices[c]);
    colors.push(vertexColors[a]); 
    points.push(vertices[a]); 
    colors.push(vertexColors[a]); 
    points.push(vertices[c]); 
    colors.push(vertexColors[a]); 
    points.push(vertices[d]); 
}


function colorCube() {
    quad( 1, 0, 3, 2 );
    quad( 2, 3, 7, 6 );
    quad( 3, 0, 4, 7 );
    quad( 6, 5, 1, 2 );
    quad( 4, 5, 6, 7 );
    quad( 5, 4, 0, 1 );
}

//____________________________________________

// Remmove when scale in MV.js supports scale matrices

function scale4(a, b, c) {
   var result = mat4();
   result[0][0] = a;
   result[1][1] = b;
   result[2][2] = c;
   return result;
}


//--------------------------------------------------

function updateDisplays() {
  document.getElementById("base").innerText = theta[0].toFixed(2);
	document.getElementById("lower").innerText = theta[1].toFixed(2);
	document.getElementById("upper").innerText = theta[2].toFixed(2);
}


window.onload = function init() {

    canvas = document.getElementById( "gl-canvas" );
    
    gl = WebGLUtils.setupWebGL( canvas );
    if ( !gl ) { alert( "WebGL isn't available" ); }
    
    gl.viewport( 0, 0, canvas.width, canvas.height );
    
    gl.clearColor( 1.0, 1.0, 1.0, 1.0 );
    gl.enable( gl.DEPTH_TEST ); 
      
    // Set aspect ratio of canvas
    aspect =  canvas.width/canvas.height;

    //
    //  Load shaders and initialize attribute buffers
    //
    program = initShaders( gl, "vertex-shader", "fragment-shader" );
    
    gl.useProgram( program );

    colorCube();
    
    // Load shaders and use the resulting shader program
    
    program = initShaders( gl, "vertex-shader", "fragment-shader" );    
    gl.useProgram( program );

    // Create and initialize  buffer objects
    
    vBuffer = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, vBuffer );
    gl.bufferData( gl.ARRAY_BUFFER, flatten(points), gl.STATIC_DRAW );
    
    var vPosition = gl.getAttribLocation( program, "vPosition" );
    gl.vertexAttribPointer( vPosition, 4, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vPosition );

    cBuffer = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, cBuffer );
    gl.bufferData( gl.ARRAY_BUFFER, flatten(colors), gl.STATIC_DRAW );

    var vColor = gl.getAttribLocation( program, "vColor" );
    gl.vertexAttribPointer( vColor, 4, gl.FLOAT, false, 0, 0 );
    gl.enableVertexAttribArray( vColor );

  
    updateDisplays();
    document.getElementById("Button1").onclick = function(){ theta[0] -= 10; updateDisplays(); };
    document.getElementById("Button2").onclick = function(){ theta[0] += 10; updateDisplays();};
    document.getElementById("Button3").onclick = function(){ theta[1] -= 10; updateDisplays(); };
    document.getElementById("Button4").onclick = function(){ theta[1] += 10; updateDisplays(); };
    document.getElementById("Button5").onclick = function(){ theta[2] -= 10; updateDisplays(); };
    document.getElementById("Button6").onclick = function(){ theta[2] += 10; updateDisplays(); };
    document.getElementById("Button7").onclick = function(){ theta = [0,0,0]; updateDisplays(); };

  
    modelViewMatrixLoc = gl.getUniformLocation(program, "modelViewMatrix");

    // projectionMatrix = ortho(-10, 10, -10, 10, -10, 10);
    projectionMatrix = perspective(fovy, aspect, near, far);

    gl.uniformMatrix4fv( gl.getUniformLocation(program, "projectionMatrix"),  false, flatten(projectionMatrix) );
    
    render();
}

//----------------------------------------------------------------------------


function base() {
    var s = scale4(BASE_WIDTH, BASE_HEIGHT, BASE_WIDTH);
    var instanceMatrix = mult( translate( 0.0, 0.5 * BASE_HEIGHT, 0.0 ), s);
    var t = mult(modelViewMatrix, instanceMatrix);
    gl.uniformMatrix4fv(modelViewMatrixLoc,  false, flatten(t) );
    gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
}

//----------------------------------------------------------------------------


function upperArm() {
    var s = scale4(UPPER_ARM_WIDTH, UPPER_ARM_HEIGHT, UPPER_ARM_WIDTH);
    var instanceMatrix = mult(translate( 0.0, 0.5 * UPPER_ARM_HEIGHT, 0.0 ),s);    
    var t = mult(modelViewMatrix, instanceMatrix);
    gl.uniformMatrix4fv( modelViewMatrixLoc,  false, flatten(t) );
    gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
}

//----------------------------------------------------------------------------


function lowerArm()
{
    var s = scale4(LOWER_ARM_WIDTH, LOWER_ARM_HEIGHT, LOWER_ARM_WIDTH);
    var instanceMatrix = mult( translate( 0.0, 0.5 * LOWER_ARM_HEIGHT, 0.0 ), s);
    var t = mult(modelViewMatrix, instanceMatrix);
    gl.uniformMatrix4fv( modelViewMatrixLoc,  false, flatten(t) );
    gl.drawArrays( gl.TRIANGLES, 0, NumVertices );
}

//----------------------------------------------------------------------------


var render = function() {

    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
    
    modelViewMatrix = lookAt(eye, at, up);
    modelViewMatrix = mult(modelViewMatrix, rotate(theta[Base], 0, 1, 0 ));
    base();
 
    modelViewMatrix = mult(modelViewMatrix, translate(0.0, BASE_HEIGHT, 0.0)); 
    modelViewMatrix = mult(modelViewMatrix, rotate(theta[LowerArm], 0, 0, 1 ));
    lowerArm();

    modelViewMatrix  = mult(modelViewMatrix, translate(0.0, LOWER_ARM_HEIGHT, 0.0));
    modelViewMatrix  = mult(modelViewMatrix, rotate(theta[UpperArm], 0, 0, 1) );
    upperArm();

    requestAnimFrame(render);
}
!
999px

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