Axis Rotation looking down -Z

by Gregg Tavares

HTML

<canvas id="c"></canvas>
<script id="vs" type="notjs">
uniform mat4 u_worldViewProjection;
uniform vec3 u_lightWorldPos;
uniform mat4 u_world;
uniform mat4 u_viewInverse;
uniform mat4 u_worldInverseTranspose;

attribute vec4 position;
attribute vec3 normal;
attribute vec2 texcoord;

varying vec4 v_position;
varying vec2 v_texCoord;
varying vec3 v_normal;
varying vec3 v_surfaceToLight;
varying vec3 v_surfaceToView;

void main() {
  v_texCoord = texcoord;
  v_position = u_worldViewProjection * position;
  v_normal = (u_worldInverseTranspose * vec4(normal, 0)).xyz;
  v_surfaceToLight = u_lightWorldPos - (u_world * position).xyz;
  v_surfaceToView = (u_viewInverse[3] - (u_world * position)).xyz;
  gl_Position = v_position;
}
</script>
<script id="fs" type="notjs">
precision mediump float;

varying vec4 v_position;
varying vec2 v_texCoord;
varying vec3 v_normal;
varying vec3 v_surfaceToLight;
varying vec3 v_surfaceToView;

uniform vec4 u_lightColor;
uniform vec4 u_ambient;
uniform sampler2D u_diffuse;
uniform vec4 u_diffuseMult;
uniform vec4 u_specular;
uniform float u_shininess;
uniform float u_specularFactor;

vec4 lit(float l ,float h, float m) {
  return vec4(1.0,
              max(l, 0.0),
              (l > 0.0) ? pow(max(0.0, h), m) : 0.0,
              1.0);
}

void main() {
  vec4 diffuseColor = texture2D(u_diffuse, v_texCoord) * u_diffuseMult;
  vec3 a_normal = normalize(v_normal);
  vec3 surfaceToLight = normalize(v_surfaceToLight);
  vec3 surfaceToView = normalize(v_surfaceToView);
  vec3 halfVector = normalize(surfaceToLight + surfaceToView);
  vec4 litR = lit(dot(a_normal, surfaceToLight),
                    dot(a_normal, halfVector), u_shininess);
  vec4 outColor = vec4((
  u_lightColor * (diffuseColor * litR.y + diffuseColor * u_ambient +
                u_specular * litR.z * u_specularFactor)).rgb,
      diffuseColor.a);
  gl_FragColor = outColor;
}
</script>
<script src="https://twgljs.org/dist/4.x/twgl-full.min.js"></script>

CSS

body {
          margin: 0;
          font-family: monospace;
      }
      canvas {
          display: block;
          width: 100vw;
          height: 100vh;
      }
      #b {
        position: absolute;
        top: 10px;
        width: 100%;
        text-align: center;
        z-index: 2;
      }

JavaScript

"use strict";
    
    /* global twgl, document, requestAnimationFrame */
    
    const m4 = twgl.m4;
    const gl = document.querySelector("#c").getContext("webgl");
    const programInfo = twgl.createProgramInfo(gl, ["vs", "fs"]);

    const bufferInfo = twgl.primitives.createCubeBufferInfo(gl, 2);

    const tex = twgl.createTexture(gl, {
      min: gl.NEAREST,
      mag: gl.NEAREST,
      src: [
        255, 255, 255, 255,
        192, 192, 192, 255,
        192, 192, 192, 255,
        255, 255, 255, 255,
      ],
    });

    const uniforms = {
      u_lightWorldPos: [5, 18, 20],
      u_lightColor: [1, 1, 1, 1],
      u_ambient: [0, 0, 0, 1],
      u_specular: [1, 1, 1, 1],
      u_shininess: 150,
      u_specularFactor: 1,
      u_diffuse: tex,
    };

    function render(time) {
      time *= 0.001;
      twgl.resizeCanvasToDisplaySize(gl.canvas);
      gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

      gl.enable(gl.DEPTH_TEST);
      gl.enable(gl.CULL_FACE);
      gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

      const fov = 60 * Math.PI / 180;
      const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
      const zNear = 0.5;
      const zFar = 100;
      const projection = m4.perspective(fov, aspect, zNear, zFar);
      const viewProjection = projection;

      uniforms.u_viewInverse = m4.identity();

      ['rotateX', 'rotateY', 'rotateZ'].forEach((axis, i) => {
         const world = m4.translation([(i - 1) * 3, 0, -10]);
         m4[axis](world, time, world);

         uniforms.u_world = world;
         uniforms.u_worldInverseTranspose = m4.transpose(m4.inverse(world));
         uniforms.u_worldViewProjection = m4.multiply(viewProjection, world);
         uniforms.u_diffuseMult = [0.5, 0.5, 0.5, 1];
         uniforms.u_diffuseMult[i] = 1;

         gl.useProgram(programInfo.program);
         twgl.setBuffersAndAttributes(gl, programInfo, bufferInfo);
         twgl.setUniforms(programInfo, uniforms);
        ...