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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

            
              <html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>Draw Elements</title>
  </head>

  <body onload="main()">
    <canvas id="webgl" width="400" height="400"></canvas>
  </body>
</html>

            
          
!
            
              // 顶点着色器源码
var VSHADER_SOURCE =
  'attribute vec4 a_Position;\n' +
  'void main() {\n' +
  '  gl_Position = a_Position;\n' +
  '}\n';

// 片元着色器源码
var FSHADER_SOURCE =
  'void main() {\n' +
  '  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n' +
  '}\n';

function main() {

  // Part 1
  var canvas = document.getElementById('webgl');
  var gl = canvas.getContext('experimental-webgl');
  if (!gl) {
    console.warn('获取WebGL上下文失败');
    return;
  }
  // 至此获取了webgl上下文gl

  // Part2
  var vshader = gl.createShader(gl.VERTEX_SHADER),
    fshader = gl.createShader(gl.FRAGMENT_SHADER);
  gl.shaderSource(vshader, VSHADER_SOURCE);
  gl.shaderSource(fshader, FSHADER_SOURCE);
  gl.compileShader(vshader);
  gl.compileShader(fshader);
  var program = gl.createProgram();
  gl.attachShader(program, vshader);
  gl.attachShader(program, fshader);
  gl.linkProgram(program);
  // 至此将着色器源码编译为了着色器程序program

  gl.useProgram(program);

  // Part3
  var varray = new Float32Array([-0.5, -0.5, 0, 0.5, -0.5, 0, 0, 0, 0, 0.5, 0, 0, 0.5, 0.5, 0])
  var vbuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vbuffer);
  gl.bufferData(gl.ARRAY_BUFFER, varray, gl.STATIC_DRAW);
  // 至此将三个顶点数据填入gl.ARRAY_BUFFER中
  var aloc = gl.getAttribLocation(program, 'a_Position');
  gl.vertexAttribPointer(aloc, 3, gl.FLOAT, false, 0, 0);
  gl.enableVertexAttribArray(aloc);
  // 至此将gl.ARRAY_BUFFER中的数据分配给了着色器中的attribute变量a_Position
  
  var iarray = new Uint8Array([0,1,2,2,3,4]);
  var ibuffer = gl.createBuffer(gl.ARRAY_BUFFER, ibuffer);
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, ibuffer);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, iarray, gl.STATIC_DRAW);
  
  
  // Part4
  gl.clearColor(0, 0, 0, 1);
  gl.clear(gl.COLOR_BUFFER_BIT);
  gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_BYTE, 0);
  // 至此画出了三角形
}

            
          
!
999px
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