MinaGabriel/RotatingTriangle.html

## RotatingTriangle.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8"/>
    <title>Translate a Triangle</title>

<body onload="main()">
<canvas id="webgl" width="400" height="400">
    Please use a browser that supports "canvas"
</canvas>
</body>

<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/webgl-utils.js"></script>
<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/webgl-debug.js"></script>
<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/cuon-utils.js"></script>
<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/cuon-matrix.js"></script>
<script type="text/javascript">

    // RotatingTriangle.js (c) 2012 matsuda
    // Vertex shader program
    var VSHADER_SOURCE =
        'attribute vec4 a_Position;\n' +
        'uniform mat4 u_ModelMatrix;\n' +
        'void main() {\n' +
        '  gl_Position = u_ModelMatrix * a_Position;\n' +
        '}\n';

    // Fragment shader program
    var FSHADER_SOURCE =
        'void main() {\n' +
        '  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
        '}\n';

    // Rotation angle (degrees/second)
    var ANGLE_STEP = 45.0;

    function main() {
        // Retrieve <canvas> element
        var canvas = document.getElementById('webgl');

        // Get the rendering context for WebGL
        var gl = getWebGLContext(canvas);
        if (!gl) {
            console.log('Failed to get the rendering context for WebGL');
            return;
        }

        // Initialize shaders
        if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
            console.log('Failed to intialize shaders.');
            return;
        }

        // Write the positions of vertices to a vertex shader
        var n = initVertexBuffers(gl);
        if (n < 0) {
            console.log('Failed to set the positions of the vertices');
            return;
        }

        // Specify the color for clearing <canvas>
        gl.clearColor(0.0, 0.0, 0.0, 1.0);

        // Get storage location of u_ModelMatrix
        var u_ModelMatrix = gl.getUniformLocation(gl.program, '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() {
            currentAngle = animate(currentAngle);  // Update the rotation angle
            draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix);   // Draw the triangle
            requestAnimationFrame(tick, canvas); // Request that the browser calls tick
        };
        tick();
    }

    // Last time that this function was called
    var g_last = Date.now();

    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;
        return newAngle %= 360;
    }

    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

        // Create a buffer object
        var vertexBuffer = gl.createBuffer();
        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) {
            console.log('Failed to get the storage location of a_Position');
            return -1;
        }
        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

        // Enable the assignment to a_Position variable
        gl.enableVertexAttribArray(a_Position);

        return n;
    }

    function draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix) {
        // Set the rotation matrix
        modelMatrix.setRotate(currentAngle, 0, 0, 1); // Rotation angle, rotation axis (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 rectangle
        gl.drawArrays(gl.TRIANGLES, 0, n);
    }


</script>
</head>
</html>
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="utf-8"/>
	<title>Translate a Triangle</title>

	<body onload="main()">
	<canvas id="webgl" width="400" height="400">
	Please use a browser that supports "canvas"
	</canvas>
	</body>

	<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/webgl-utils.js"></script>
	<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/webgl-debug.js"></script>
	<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/cuon-utils.js"></script>
	<script src="https://rawgit.com/huningxin/webglbook_examples/master/lib/cuon-matrix.js"></script>
	<script type="text/javascript">

	// RotatingTriangle.js (c) 2012 matsuda
	// Vertex shader program
	var VSHADER_SOURCE =
	'attribute vec4 a_Position;\n' +
	'uniform mat4 u_ModelMatrix;\n' +
	'void main() {\n' +
	' gl_Position = u_ModelMatrix * a_Position;\n' +
	'}\n';

	// Fragment shader program
	var FSHADER_SOURCE =
	'void main() {\n' +
	' gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
	'}\n';

	// Rotation angle (degrees/second)
	var ANGLE_STEP = 45.0;

	function main() {
	// Retrieve <canvas> element
	var canvas = document.getElementById('webgl');

	// Get the rendering context for WebGL
	var gl = getWebGLContext(canvas);
	if (!gl) {
	console.log('Failed to get the rendering context for WebGL');
	return;
	}

	// Initialize shaders
	if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
	console.log('Failed to intialize shaders.');
	return;
	}

	// Write the positions of vertices to a vertex shader
	var n = initVertexBuffers(gl);
	if (n < 0) {
	console.log('Failed to set the positions of the vertices');
	return;
	}

	// Specify the color for clearing <canvas>
	gl.clearColor(0.0, 0.0, 0.0, 1.0);

	// Get storage location of u_ModelMatrix
	var u_ModelMatrix = gl.getUniformLocation(gl.program, '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() {
	currentAngle = animate(currentAngle); // Update the rotation angle
	draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix); // Draw the triangle
	requestAnimationFrame(tick, canvas); // Request that the browser calls tick
	};
	tick();
	}

	// Last time that this function was called
	var g_last = Date.now();

	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;
	return newAngle %= 360;
	}

	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

	// Create a buffer object
	var vertexBuffer = gl.createBuffer();
	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) {
	console.log('Failed to get the storage location of a_Position');
	return -1;
	}
	gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);

	// Enable the assignment to a_Position variable
	gl.enableVertexAttribArray(a_Position);

	return n;
	}

	function draw(gl, n, currentAngle, modelMatrix, u_ModelMatrix) {
	// Set the rotation matrix
	modelMatrix.setRotate(currentAngle, 0, 0, 1); // Rotation angle, rotation axis (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 rectangle
	gl.drawArrays(gl.TRIANGLES, 0, n);
	}


	</script>
	</head>
	</html>