cube in webgl

by Gregg Tavares

HTML

<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://webglfundamentals.org/webgl/resources/webgl-lessons-helper.js"></script>
<script src="https://webglfundamentals.org/webgl/lessons/resources/3d-math.js"></script>
<!-- vertex shader -->
<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
uniform mat4 u_worldViewProjection;

void main() {
   gl_Position = u_worldViewProjection * a_position;
}
</script>
<!-- fragment shader -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
void main() {
   gl_FragColor = vec4(0,0,0,1);
}
</script>
<canvas id="c"></canvas>

CSS

body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block }

JavaScript

"use strict";

var m = ThreeDMath;

function main() {
  var cubeVertices = [
    -1, -1, -1,
     1, -1, -1,
     1,  1, -1,
    -1,  1, -1,
    -1, -1,  1,
     1, -1,  1,
     1,  1,  1,
    -1,  1,  1,
  ];
  var indices = [
    0, 1,
    1, 2,
    2, 3,
    3, 0,
    4, 5,
    5, 6,
    6, 7,
    7, 4,
    0, 4,
    1, 5,
    2, 6,
    3, 7,
  ];

  var canvas = document.getElementById("c");
  var gl = canvas.getContext("webgl");
  if (!gl) {
    alert("no webgl");
    return;
  }

  var program = webglUtils.createProgramFromScripts(
      gl, ["2d-vertex-shader", "2d-fragment-shader"]);
  gl.useProgram(program);

  var positionLoc = gl.getAttribLocation(program, "a_position");
  var worldViewProjectionLoc =
      gl.getUniformLocation(program, "u_worldViewProjection");

  var buffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
  gl.bufferData(
      gl.ARRAY_BUFFER,
      new Float32Array(cubeVertices),
      gl.STATIC_DRAW);
  gl.enableVertexAttribArray(positionLoc);
  gl.vertexAttribPointer(positionLoc, 3, gl.FLOAT, false, 0, 0);

  var buffer = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer);
  gl.bufferData(
      gl.ELEMENT_ARRAY_BUFFER,
      new Uint16Array(indices),
      gl.STATIC_DRAW);

  function render(clock) {
    clock *= 0.001;

    var scale = 4;

    webglUtils.resizeCanvasToDisplaySize(gl.canvas, window.devicePixelRatio);

    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.clear(gl.COLOR_BUFFER_BIT);

    var fieldOfView = Math.PI * 0.25;
    var aspect = canvas.clientWidth / canvas.clientHeight;
    var projection = m.perspective(fieldOfView, aspect, 0.0001, 500);
    var radius = 5;
    var eye = [
        Math.sin(clock) * radius,
        1,
        Math.cos(clock) * radius,
    ];
    var target = [0, 0, 0];
    var up = [0, 1, 0];
    var view = m.lookAt(eye, target, up);

    var worldViewProjection = m.multiplyMatrix(view, projection);
   ...