var canvas = document.getElementById('my_Canvas');
var gl = canvas.getContext('experimental-webgl');
// Add two points to canvas
drawPoint(0.5, 0.5, 0);
drawPoint(-0.5, -0.5, 0);
// Add another 5 seconds later
setTimeout(drawLater, 5000);
function drawALittleLater(){
drawPoint(-0.5, 0.5, 0);
}
function drawLater(){
drawPoint(0.5, -0.5, 0);
}
function drawPoint(x, y, z){
var vertices = [
x, y, z
];
// Create an empty buffer object to store the 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);
/*=========================Shaders========================*/
// vertex shader source code
var vertCode =
'attribute vec3 coordinates;' +
'void main(void) {' +
' gl_Position = vec4(coordinates, 1.0);' +
'gl_PointSize = 10.0;'+
'}';
// Create a vertex shader object
var vertShader = gl.createShader(gl.VERTEX_SHADER);
// Attach vertex shader source code
gl.shaderSource(vertShader, vertCode);
// Compile the vertex shader
gl.compileShader(vertShader);
// fragment shader source code
var fragCode =
'void main(void) {' +
' gl_FragColor = vec4(1.0, 0.0, 0.0, 1);' +
'}';
// Create fragment shader object
var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
// Attach fragment shader source code
gl.shaderSource(fragShader, fragCode);
// 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 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);
// 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 primitive ===============*/
// Enable the depth test
gl.enable(gl.DEPTH_TEST);
// Set the view port
gl.viewport(0,0,canvas.width,canvas.height);
// Draw the triangle
gl.drawArrays(gl.POINTS, 0, 1);
}
<html>
<body>
<canvas width = "200" height = "200" id = "my_Canvas"></canvas>
<script>
</script>
</body>
</html>
