WebGL笔记：js中矩阵库的使用

矩阵库

• 手写矩阵，其实很麻烦，可以将其模块化
• 市面上已经有许多开源的矩阵库
  • 比如《WebGL 编程指南》里的 cuon-matrix.js
  • three.js 的 Matrix3 和 Matrix4 对象

three.js的 Matrix4 对象的用法

1 ）核心代码

• 1.引入Matrix4对象

  import { Matrix4 } from 'https://unpkg.com/three/build/three.module.js';
  

• 2.实例化矩阵对象，在其中写入旋转信息

  const matrix = new Matrix4()
  matrix.makeRotationZ(Math.PI/6)
  

• 3.基于matrix 对象的elements 属性，修改uniform 变量

  const u_Matrix=gl.getUniformLocation(gl.program,'u_Matrix')
  gl.uniformMatrix4fv(u_Matrix,false,matrix.elements)
  

2 ）完整代码

<canvas id="canvas"></canvas>
<script id="vertexShader" type="x-shader/x-vertex">
  attribute vec4 a_Position;
  // 列主序
  uniform mat4 u_Matrix;
  void main() {
    gl_Position = u_Matrix * a_Position;
  }
</script>
<script id="fragmentShader" type="x-shader/x-fragment">
  void main() {
    gl_FragColor = vec4(1.0, 1.0, 0.0, 1.0);
  }
</script>
<script type="module">
  import { initShaders } from './utils.js';
  import { Matrix4 } from 'https://unpkg.com/three/build/three.module.js';

  const canvas = document.getElementById('canvas');
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;
  const gl = canvas.getContext('webgl');

  const vsSource = document.getElementById('vertexShader').innerText;
  const fsSource = document.getElementById('fragmentShader').innerText;
  initShaders(gl, vsSource, fsSource);

  const vertices = new Float32Array([
    0.0, 0.1,
    -0.1, -0.1,
    0.1, -0.1
  ]);

  const vertexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
  const a_Position = gl.getAttribLocation(gl.program, 'a_Position');
  gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 0, 0);
  gl.enableVertexAttribArray(a_Position);

  const u_Matrix = gl.getUniformLocation(gl.program, 'u_Matrix');
  let angle = 0.1;
  const m4 = new Matrix4();
  m4.makeRotationZ(angle);
  gl.uniformMatrix4fv(u_Matrix, false, m4.elements);

  gl.clearColor(0.0, 0.0, 0.0, 1.0);
  gl.clear(gl.COLOR_BUFFER_BIT);
  gl.drawArrays(gl.TRIANGLES, 0, 3);

  !(function animate() {
    angle += 0.05;
    m4.makeRotationZ(angle);
    gl.uniformMatrix4fv(u_Matrix, false, m4.elements);

    gl.clear(gl.COLOR_BUFFER_BIT);
    gl.drawArrays(gl.TRIANGLES, 0, 3);
    requestAnimationFrame(animate);
  })()
</script>