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<html>
  <head>
    <title>Earth and Mars</title>
    <script src="resources/J3DI.js"> </script>
    <script src="resources/J3DIMath.js" type="text/javascript"> </script>
    
    <script id="vshader" type="x-shader/x-vertex">
        uniform mat4 u_modelViewProjMatrix;
        uniform mat4 u_normalMatrix;
        uniform vec3 lightDir;

        attribute vec3 vNormal;
        attribute vec4 vTexCoord;
        attribute vec4 vPosition;
        
        varying float v_Dot;
        varying vec2 v_texCoord;
        
        void main()
        {
            gl_Position = u_modelViewProjMatrix * vPosition;
            v_texCoord = vTexCoord.st;
            vec4 transNormal = u_normalMatrix * vec4(vNormal,1);
            v_Dot = max(dot(transNormal.xyz, lightDir), 0.0);
        }
    </script>

    <script id="fshader" type="x-shader/x-fragment">
#ifdef GL_ES
    precision mediump float;
#endif
    
        uniform sampler2D sampler2d;

        varying float v_Dot;
        varying vec2 v_texCoord;
        
        void main()
        {
            vec4 color = texture2D(sampler2d,v_texCoord);
            color += vec4(0.1,0.1,0.1,1);
            gl_FragColor = vec4(color.xyz * v_Dot, color.a);
        }
    </script>

    <script>
        function init()
        {
            var gl = initWebGL("example", "vshader", "fshader", 
                                [ "vNormal", "vTexCoord", "vPosition"],
                                [ 0, 0, 0, 1 ], 10000);

            gl.uniform3f(gl.getUniformLocation(gl.program, "lightDir"), 0, 0, 1);
            gl.uniform1i(gl.getUniformLocation(gl.program, "sampler2d"), 0);

            gl.enable(gl.TEXTURE_2D);

            gl.sphere = makeSphere(gl, 1, 30, 30);
            
            // get the images
            earthTexture = loadImageTexture(gl, "resources/earthmap1k.jpg");
            marsTexture = loadImageTexture(gl, "resources/mars500x250.png");

            return gl;
        }
        
        width = -1;
        height = -1;
        
        function reshape(ctx)
        {
            var canvas = document.getElementById('example');
            if (canvas.width == width && canvas.width == height)
                return;

            width = canvas.width;
            height = canvas.height;
            
            ctx.viewport(0, 0, width, height);

            ctx.perspectiveMatrix = new J3DIMatrix4();
            ctx.perspectiveMatrix.perspective(30, width/height, 1, 10000);
            ctx.perspectiveMatrix.lookat(0,0,6, 0, 0, 0, 0, 1, 0);
        }
        
        function drawOne(ctx, angle, x, y, z, scale, texture)
        {
            // setup VBOs
            ctx.enableVertexAttribArray(0);
            ctx.enableVertexAttribArray(1);
            ctx.enableVertexAttribArray(2);

            ctx.bindBuffer(ctx.ARRAY_BUFFER, ctx.sphere.vertexObject);
            ctx.vertexAttribPointer(2, 3, ctx.FLOAT, false, 0, 0);
            
            ctx.bindBuffer(ctx.ARRAY_BUFFER, ctx.sphere.normalObject);
            ctx.vertexAttribPointer(0, 3, ctx.FLOAT, false, 0, 0);
            
            ctx.bindBuffer(ctx.ARRAY_BUFFER, ctx.sphere.texCoordObject);
            ctx.vertexAttribPointer(1, 2, ctx.FLOAT, false, 0, 0);

            ctx.bindBuffer(ctx.ELEMENT_ARRAY_BUFFER, ctx.sphere.indexObject);

            // generate the model-view matrix
            var mvMatrix = new J3DIMatrix4();
            mvMatrix.translate(x,y,z);
            mvMatrix.rotate(30, 1,0,0);
            mvMatrix.rotate(angle, 0,1,0);
            mvMatrix.scale(scale, scale, scale);

            // construct the normal matrix from the model-view matrix
            var normalMatrix = new J3DIMatrix4(mvMatrix);
            normalMatrix.invert();
            normalMatrix.transpose();
            normalMatrix.setUniform(ctx, ctx.getUniformLocation(ctx.program, "u_normalMatrix"), false);
            
            // construct the model-view * projection matrix
            var mvpMatrix = new J3DIMatrix4(ctx.perspectiveMatrix);
            mvpMatrix.multiply(mvMatrix);
            mvpMatrix.setUniform(ctx, ctx.getUniformLocation(ctx.program, "u_modelViewProjMatrix"), false);

            ctx.bindTexture(ctx.TEXTURE_2D, texture);
            ctx.drawElements(ctx.TRIANGLES, ctx.sphere.numIndices, ctx.UNSIGNED_SHORT, 0);
        }
        
        function drawPicture(ctx)
        {
            reshape(ctx);
            ctx.clear(ctx.COLOR_BUFFER_BIT | ctx.DEPTH_BUFFER_BIT);
            
            drawOne(ctx, currentAngle, -1, 0, 0, 1, earthTexture);
            drawOne(ctx, -currentAngle, 1, 0, 0, 0.6, marsTexture);
            ctx.flush();
            
            framerate.snapshot();
            
            currentAngle += incAngle;
            if (currentAngle > 360)
                currentAngle -= 360;
        }
        
        function start()
        {
            var c = document.getElementById("example");
            var w = Math.floor(window.innerWidth * 0.9);
            var h = Math.floor(window.innerHeight * 0.9);

            c.width = w;
            c.height = h;

            var ctx = init();
            currentAngle = 0;
            incAngle = 0.2;
            var f = function() { drawPicture(ctx) };
            setInterval(f, 10);
            framerate = new Framerate("framerate");
        }
    </script>
    <style type="text/css">
        canvas {
            border: 2px solid black;
        }
    </style>
  </head>
  <body onload="start()">
    <canvas id="example">
    There is supposed to be an example drawing here, but it's not important.
    </canvas>
    <div id="framerate"></div>
    <div id="console"></div>
  </body>
</html>