2.- contexto canvas WebGL

<!-- define functions to be used later -->
<script type="text/javascript">

    var GLwall;

    function GLdraw(){

    }

    function startGL(canvas) {
        GLwall = null;
        // Try to grab the standard context. If it fails, fallback to experimental.
        GLwall = canvas.getContext("webgl", {alpha: false}) ||
                 canvas.getContext("experimental-webgl", {alpha: false});

        if (!GLwall) {
            alert("Could not initialise WebGL, sorry :-(");
        }else{
            canvas.width = 400;
            canvas.height = 300;
            GLwall.viewport(0, 0, canvas.width, canvas.height);
            GLdraw();
        }
    }
</script>


<!-- define the canvas element -->
<canvas id="webglTest1" width=400 height=300 ></canvas>

<!-- call the startGL function to start the canvas element -->
<script type="text/javascript">
    var startTest1 = document.getElementById('webglTest1');
    startGL(startTest1);
</script>