Why is not WebGL drawing point? - buffer

Question

I can't understand what I do wrong, my mind going to blow
I just pushing value to list and want to draw point using this list like vertices(0)=x,vertices(1)=y and what to do if I have much point like
vertices(0)=x1,vertices(1)=y1,vertices(2)=x2,vertices(3)=y2 (about 600 points)?
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n'+'void main() {\n'+' gl_Position = a_Position;\n' + ' gl_PointSize = 10.0;\n' + '}\n';
var FSHADER_SOURCE='void main() {\n'+'gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' + '}\n';
function main() {
var canvas = document.getElementById('webgl');
var gl = getWebGLContext(canvas);
if (!gl) {console.log('Failed to get the rendering context for WebGL');
return;}
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
console.log('Failed to intialize shaders.'); return; }
var n = initVertexBuffers(gl);
if (n < 0) {console.log('Failed to set the positions of the vertices');
return;}
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.POINTS, 0, n);
}
var vertices = [];
function initVertexBuffers(gl) {vertices.push(0.1);vertices.push(0.3);
var n = vertices.length/2; var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) { console.log('Failed to create the buffer object');
return -1; }
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
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);
gl.enableVertexAttribArray(a_Position); return n; }
And file
initVertexBuffers
function initShaders(gl, vshader, fshader) {
var program = createProgram(gl, vshader, fshader);
if (!program) {
console.log('Failed to create program');
return false;
} gl.useProgram(program);gl.program = program;return true; }
function createProgram(gl, vshader, fshader) {
var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vshader);
var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fshader);
if (!vertexShader || !fragmentShader) { return null;}
var program = gl.createProgram();
if (!program) {return null;}
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
var linked = gl.getProgramParameter(program, gl.LINK_STATUS);
if (!linked) {
var error = gl.getProgramInfoLog(program);
console.log('Failed to link program: ' + error);
gl.deleteProgram(program);
gl.deleteShader(fragmentShader);
gl.deleteShader(vertexShader);
return null;
} return program;}
function loadShader(gl, type, source) {
var shader = gl.createShader(type);
if (shader == null) {console.log('unable to create shader');
return null;}
gl.shaderSource(shader, source);
gl.compileShader(shader);
var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (!compiled) {var error = gl.getShaderInfoLog(shader);
console.log('Failed to compile shader: ' + error);
gl.deleteShader(shader);return null;}return shader;}
function getWebGLContext(canvas, opt_debug) {
var gl = WebGLUtils.setupWebGL(canvas);
if (!gl) return null;
if (arguments.length < 2 || opt_debug) {
gl = WebGLDebugUtils.makeDebugContext(gl);
} return gl; }

Answer 1

At a glance this code
var vertices = [];
function initVertexBuffers(gl) {
vertices.push(0.1);
vertices.push(0.3);
var n = vertices.length/2;
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create the buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
won't work because gl.bufferData does not take JavaScript native arrays. It only takes typed arrays.
You probably want this
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
var VSHADER_SOURCE = `
attribute vec4 a_Position;
void main() {
gl_Position = a_Position;
gl_PointSize = 10.0;
}
`;
var FSHADER_SOURCE = `
void main() {
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
`;
function main() {
var canvas = document.getElementById('webgl');
var gl = canvas.getContext("webgl");
if (!gl)
{
console.log('Failed to retrieve the <canvas> element');
return;
}
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE))
{
console.log('Failed to intialize shaders.');
return;
}
gl.clearColor(0.0, 0.0, 0.0, 0.0);
gl.clear(gl.COLOR_BUFFER_BIT);
var n = initVertexBuffers(gl);
if (n < 0) {console.log('Failed to set the positions of the vertices');
return;}
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.POINTS, 0, n);
}
var vertices = [];
function initVertexBuffers(gl) {
vertices.push(0.1);
vertices.push(0.3);
var n = vertices.length/2;
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create the buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
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);
gl.enableVertexAttribArray(a_Position);
return n;
}
// THIS IS A POORLY WRITTEN FUNCTION!!!!
// Normal WebGL pages use multiple shader programs
// therefore you should **NEVER** assign values to
// the gl object!!!
function initShaders(gl, vsrc, fsrc) {
gl.program = twgl.createProgram(gl, [vsrc, fsrc]);
gl.useProgram(gl.program);
return !!gl.program;
}
main();
<script src="https://twgljs.org/dist/3.x/twgl.min.js"></script>
<canvas id="webgl"></canvas>