init

function init() {

    canvas = document.getElementById('webgl');
    gl     = getWebGLContext(canvas, false);

    canvas.onmousedown= onmousedown;
    canvas.onmouseup= onmouseup;
    canvas.onmousemove= onmousemove;

    // Initialize the program object and its uniforms. no error check

    initShaders(gl, document.getElementById('vertexShader').text,
                    document.getElementById('fragmentShader').text);

  // Link the shader attributes to the vertex buffer object.

    var projectionMatrixLocation = gl.getUniformLocation(gl.program, 'projectionMatrix');
    var modelMatrixLocation = gl.getUniformLocation(gl.program, 'modelMatrix');
    var lightDirectionLocation = gl.getUniformLocation(gl.program, 'lightDirection');
    var lightColorLocation = gl.getUniformLocation(gl.program, 'lightColor');
    var objectColorLocation = gl.getUniformLocation(gl.program, 'objectColor');





    i0=0;
    i1=1;
    i2=2;
    var n;
    normals = [];

    for (n = 0; n < vertices.length; n++)
        normals.push([0,0,0]);


    for (i= 0; i<triangles.length; i++) {
        triangle = triangles[i];
        a = normalize(sub(vertices[triangle[i1]] , vertices[triangle[i0]]));
        b = normalize(sub(vertices[triangle[i2]] , vertices[triangle[i0]]));

        n = normalize(mult(a,b));

        normals[i0] = add(normals[i0], n);
        normals[i1] = add(normals[i1], n);
        normals[i2] = add(normals[i2], n);


    }

    for (n= 0; n < normals.length; n++) {
        normals[n] = normalize(normals[n]);
    }





    var vertexPositionLocation = gl.getAttribLocation(gl.program, 'vertexPosition');
    gl.enableVertexAttribArray(vertexPositionLocation);
    var vertexNormalLocation = gl.getAttribLocation(gl.program, 'vertexNormal');
    gl.enableVertexAttribArray(vertexNormalLocation);

    var positionArray;
    var normalArray;


    positionArray = new Float32Array(flatten(vertices));
    normalArray = new Float32Array(flatten(normals));
    triangleArray = new Uint16Array (flatten(triangles));

    // Initialize vertex and index buffer objects.

    positionBuffer = gl.createBuffer();
    normalBuffer  = gl.createBuffer();
    triangleBuffer   = gl.createBuffer();

    gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, positionArray, gl.STATIC_DRAW);

    gl.bindBuffer(gl.ARRAY_BUFFER, normalBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, normalArray , gl.STATIC_DRAW);

    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, triangleBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, triangleArray, gl.STATIC_DRAW);

     // Set up to render.

    gl.clearColor(1.0, 1.0, 0.8, 1.0);
    gl.enable(gl.DEPTH_TEST);

    rotateX = 0.0;
    rotateY = 0.0;
    translateZ = 3.0;

    dragging = false;

    draw();

    }