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<style>
canvas{
width:100%;
height:300px;
}
</style>
<canvas id = "my_Canvas"></canvas>
<script id="vertex-shader" type="shader">
attribute vec3 coordinates;
void main(void) {
gl_Position = vec4(coordinates, 1.0);
}
</script>
<script id="fragment-shader" type="shader">
void main(void) {
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
</script>
<script>
/*============== Creating a canvas ====================*/
var canvas = document.getElementById('my_Canvas');
gl = canvas.getContext('experimental-webgl');
/*======== Defining and storing the geometry ===========*/
var vertices = [
-0.5,0.5,0.0,
-0.5,-0.5,0.0,
0.5,-0.5,0.0,
];
indices = [0,1,2];
// Create an empty buffer object to store vertex buffer
var vertex_buffer = gl.createBuffer();
// Bind appropriate array buffer to it
gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
// Pass the vertex data to the buffer
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
// Unbind the buffer
gl.bindBuffer(gl.ARRAY_BUFFER, null);
// Create an empty buffer object to store Index buffer
var Index_Buffer = gl.createBuffer();
// Bind appropriate array buffer to it
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, Index_Buffer);
// Pass the vertex data to the buffer
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);
// Unbind the buffer
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
/*================ Shaders ====================*/
// Create a vertex shader object
var vertShader = gl.createShader(gl.VERTEX_SHADER);
// Attach vertex shader source code
gl.shaderSource(vertShader, document.querySelector('#vertex-shader').textContent);
// Compile the vertex shader
gl.compileShader(vertShader);
// Create fragment shader object
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
// Attach fragment shader source code
gl.shaderSource(fragShader, document.querySelector('#fragment-shader').textContent);
// Compile the fragmentt shader
gl.compileShader(fragShader);
// Create a shader program object to store
// the combined shader program
var shaderProgram = gl.createProgram();
// Attach a vertex shader
gl.attachShader(shaderProgram, vertShader);
// Attach a fragment shader
gl.attachShader(shaderProgram, fragShader);
// Link both the programs
gl.linkProgram(shaderProgram);
// Use the combined shader program object
gl.useProgram(shaderProgram);
/*======= Associating shaders to buffer objects =======*/
// Bind vertex buffer object
gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
// Bind index buffer object
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, Index_Buffer);
// Get the attribute location
var coord = gl.getAttribLocation(shaderProgram, "coordinates");
// Point an attribute to the currently bound VBO
gl.vertexAttribPointer(coord, 3, gl.FLOAT, false, 0, 0);
// Enable the attribute
gl.enableVertexAttribArray(coord);
/*=========Drawing the triangle===========*/
// Clear the canvas
gl.clearColor(0., 0., 0., 0.9);
// Enable the depth test
gl.enable(gl.DEPTH_TEST);
// Clear the color buffer bit
gl.clear(gl.COLOR_BUFFER_BIT);
// Set the view port
gl.viewport(0,0,canvas.width,canvas.height);
// Draw the triangle
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT,0);
</script>
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