MinaGabriel/LookAtTriangles.html

## LookAtTriangles.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">
    // LookAtRotatedTriangles.js (c) 2012 matsuda
    // Vertex shader program
    var VSHADER_SOURCE =
        'attribute vec4 a_Position;\n' +
        'attribute vec4 a_Color;\n' +
        'uniform mat4 u_ViewMatrix;\n' +
        'uniform mat4 u_ModelMatrix;\n' +
        'varying vec4 v_Color;\n' +
        'void main() {\n' +
        '  gl_Position = u_ViewMatrix * u_ModelMatrix * a_Position;\n' +
        '  v_Color = a_Color;\n' +
        '}\n';

    // Fragment shader program
    var FSHADER_SOURCE =
        '#ifdef GL_ES\n' +
        'precision mediump float;\n' +
        '#endif\n' +
        'varying vec4 v_Color;\n' +
        'void main() {\n' +
        '  gl_FragColor = v_Color;\n' +
        '}\n';

    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;
        }

        // Set the vertex coordinates and color (the blue triangle is in the front)
        var n = initVertexBuffers(gl);
        if (n < 0) {
            console.log('Failed to set the vertex information');
            return;
        }

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

        // Get the storage location of u_ViewMatrix and u_ModelMatrix
        var u_ViewMatrix = gl.getUniformLocation(gl.program, 'u_ViewMatrix');
        var u_ModelMatrix = gl.getUniformLocation(gl.program, 'u_ModelMatrix');
        if(!u_ViewMatrix || !u_ModelMatrix) {
            console.log('Failed to get the storage location of u_viewMatrix or u_ModelMatrix');
            return;
        }

        // Set the matrix to be used for to set the camera view
        var viewMatrix = new Matrix4();
        viewMatrix.setLookAt(0.20, 0.25, 0.25, 0, 0, 0, 0, 1, 0);

        // Calculate matrix for rotate
        var modelMatrix = new Matrix4();
        modelMatrix.setRotate(-10, 0, 0, 1); // Rotate around z-axis

        // Pass the view projection matrix and model matrix
        gl.uniformMatrix4fv(u_ViewMatrix, false, viewMatrix.elements);
        gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements);

        // Clear <canvas>
        gl.clear(gl.COLOR_BUFFER_BIT);

        // Draw the rectangle
        gl.drawArrays(gl.TRIANGLES, 0, n);
    }

    function initVertexBuffers(gl) {
        var verticesColors = new Float32Array([
            // Vertex coordinates and color
            0.0,  0.5,  -0.4,  0.4,  1.0,  0.4, // The back green one
            -0.5, -0.5,  -0.4,  0.4,  1.0,  0.4,
            0.5, -0.5,  -0.4,  1.0,  0.4,  0.4,

            0.5,  0.4,  -0.2,  1.0,  0.4,  0.4, // The middle yellow one
            -0.5,  0.4,  -0.2,  1.0,  1.0,  0.4,
            0.0, -0.6,  -0.2,  1.0,  1.0,  0.4,

            0.0,  0.5,   0.0,  0.4,  0.4,  1.0,  // The front blue one
            -0.5, -0.5,   0.0,  0.4,  0.4,  1.0,
            0.5, -0.5,   0.0,  1.0,  0.4,  0.4,
        ]);
        var n = 9;

        // Create a buffer object
        var vertexColorBuffer = gl.createBuffer();
        if (!vertexColorBuffer) {
            console.log('Failed to create the buffer object');
            return -1;
        }

        // Write vertex information to buffer object
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);

        var FSIZE = verticesColors.BYTES_PER_ELEMENT;
        // Assign the buffer object to a_Color and enable the assignment
        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, 3, gl.FLOAT, false, FSIZE * 6, 0);
        gl.enableVertexAttribArray(a_Position);
        // Assign the buffer object to a_Color and enable the assignment
        var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
        if(a_Color < 0) {
            console.log('Failed to get the storage location of a_Color');
            return -1;
        }
        gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 6, FSIZE * 3);
        gl.enableVertexAttribArray(a_Color);

        // Unbind the buffer object
        gl.bindBuffer(gl.ARRAY_BUFFER, null);

        return 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">
	// LookAtRotatedTriangles.js (c) 2012 matsuda
	// Vertex shader program
	var VSHADER_SOURCE =
	'attribute vec4 a_Position;\n' +
	'attribute vec4 a_Color;\n' +
	'uniform mat4 u_ViewMatrix;\n' +
	'uniform mat4 u_ModelMatrix;\n' +
	'varying vec4 v_Color;\n' +
	'void main() {\n' +
	' gl_Position = u_ViewMatrix * u_ModelMatrix * a_Position;\n' +
	' v_Color = a_Color;\n' +
	'}\n';

	// Fragment shader program
	var FSHADER_SOURCE =
	'#ifdef GL_ES\n' +
	'precision mediump float;\n' +
	'#endif\n' +
	'varying vec4 v_Color;\n' +
	'void main() {\n' +
	' gl_FragColor = v_Color;\n' +
	'}\n';

	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;
	}

	// Set the vertex coordinates and color (the blue triangle is in the front)
	var n = initVertexBuffers(gl);
	if (n < 0) {
	console.log('Failed to set the vertex information');
	return;
	}

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

	// Get the storage location of u_ViewMatrix and u_ModelMatrix
	var u_ViewMatrix = gl.getUniformLocation(gl.program, 'u_ViewMatrix');
	var u_ModelMatrix = gl.getUniformLocation(gl.program, 'u_ModelMatrix');
	if(!u_ViewMatrix \|\| !u_ModelMatrix) {
	console.log('Failed to get the storage location of u_viewMatrix or u_ModelMatrix');
	return;
	}

	// Set the matrix to be used for to set the camera view
	var viewMatrix = new Matrix4();
	viewMatrix.setLookAt(0.20, 0.25, 0.25, 0, 0, 0, 0, 1, 0);

	// Calculate matrix for rotate
	var modelMatrix = new Matrix4();
	modelMatrix.setRotate(-10, 0, 0, 1); // Rotate around z-axis

	// Pass the view projection matrix and model matrix
	gl.uniformMatrix4fv(u_ViewMatrix, false, viewMatrix.elements);
	gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements);

	// Clear <canvas>
	gl.clear(gl.COLOR_BUFFER_BIT);

	// Draw the rectangle
	gl.drawArrays(gl.TRIANGLES, 0, n);
	}

	function initVertexBuffers(gl) {
	var verticesColors = new Float32Array([
	// Vertex coordinates and color
	0.0, 0.5, -0.4, 0.4, 1.0, 0.4, // The back green one
	-0.5, -0.5, -0.4, 0.4, 1.0, 0.4,
	0.5, -0.5, -0.4, 1.0, 0.4, 0.4,

	0.5, 0.4, -0.2, 1.0, 0.4, 0.4, // The middle yellow one
	-0.5, 0.4, -0.2, 1.0, 1.0, 0.4,
	0.0, -0.6, -0.2, 1.0, 1.0, 0.4,

	0.0, 0.5, 0.0, 0.4, 0.4, 1.0, // The front blue one
	-0.5, -0.5, 0.0, 0.4, 0.4, 1.0,
	0.5, -0.5, 0.0, 1.0, 0.4, 0.4,
	]);
	var n = 9;

	// Create a buffer object
	var vertexColorBuffer = gl.createBuffer();
	if (!vertexColorBuffer) {
	console.log('Failed to create the buffer object');
	return -1;
	}

	// Write vertex information to buffer object
	gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorBuffer);
	gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);

	var FSIZE = verticesColors.BYTES_PER_ELEMENT;
	// Assign the buffer object to a_Color and enable the assignment
	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, 3, gl.FLOAT, false, FSIZE * 6, 0);
	gl.enableVertexAttribArray(a_Position);
	// Assign the buffer object to a_Color and enable the assignment
	var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
	if(a_Color < 0) {
	console.log('Failed to get the storage location of a_Color');
	return -1;
	}
	gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 6, FSIZE * 3);
	gl.enableVertexAttribArray(a_Color);

	// Unbind the buffer object
	gl.bindBuffer(gl.ARRAY_BUFFER, null);

	return n;
	}


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