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@MinaGabriel
Created November 17, 2020 17:40
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<!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>
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