我使用了WEBKIT_WEBGL_depth_texture扩展.
并初始化缓冲区.
但是我怎么能画这个帧缓冲？我现在完全被卡住了. -.-

function InitDepthtextures (){


var size = 256;

// Create a color texture
var colorTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, colorTexture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, size, size, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

// Create the depth texture
depthTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, depthTexture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.DEPTH_COMPONENT, size, size, 0, gl.DEPTH_COMPONENT, gl.UNSIGNED_SHORT, null);

framebuffer = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, colorTexture, 0);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, depthTexture, 0);


//set to default
gl.bindTexture(gl.TEXTURE_2D, null);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);

}

解决方法:

你不绘制帧缓冲区.你绘制纹理.因此,首先将纹理附加到帧缓冲区.现在,使用该帧缓冲区绑定,绘制一些东西,结果将被绘制到帧缓冲区的附件中.接下来取消绑定帧缓冲区并使用附加到帧缓冲区的纹理绘制一些内容以查看其内容.

例：

const gl = document.querySelector('#c').getContext('webgl');

const vshader = `
    attribute vec4 a_position;
    varying vec2 v_texcoord;

    void main() {
      gl_Position = a_position;
      v_texcoord = a_position.xy * 0.5 + 0.5;
    }    
`;
const fshader = `
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_sampler;
void main() {
    gl_FragColor = texture2D(u_sampler, v_texcoord);
}
`;

// compiles shaders, links program
const program = twgl.createProgram(gl, [vshader, fshader]);
gl.useProgram(program);

const positionLocation = gl.getAttribLocation(program, "a_position");

// a single triangle from top right to bottom left to bottom right
const verts = [
      1,  1,
     -1,  1,
     -1, -1,
];   
const vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(verts), gl.STATIC_DRAW);
{
  const numElements = 2;
  const type = gl.FLOAT;
  const normalize = false;
  const stride = 0;
  const offset = 0;
  gl.vertexAttribPointer(
      positionLocation, numElements, type, normalize, stride, offset);
  gl.enableVertexAttribArray(positionLocation);
}

// create an empty texture
const tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
{
  const level = 0;
  const internalFormat = gl.RGBA;
  const width = 1;
  const height = 1;
  const border = 0;
  const format = gl.RGBA;
  const type = gl.UNSIGNED_BYTE;
  const data = null;
  gl.texImage2D(gl.TEXTURE_2D, level, internalFormat, width, height, border,
                format, type, data);
}

// Create a framebuffer and attach the texture.
const fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
{
  const level = 0
  gl.framebufferTexture2D(
      gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, level);
}

// Render to the texture (using clear because it's simple)
gl.clearColor(0, 1, 0, 1); // green;
gl.clear(gl.COLOR_BUFFER_BIT);

// Now draw with the texture to the canvas
// NOTE: We clear the canvas to red so we'll know
// so anywhere that shows up green is coming from the canvas texture
// from above.
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
gl.clearColor(1, 0, 0, 1); // red
gl.clear(gl.COLOR_BUFFER_BIT);
{
  const offset = 0;
  const count = 3;
  gl.drawArrays(gl.TRIANGLES, offset, count);
}

canvas { border: 1px solid black; }

<script src="https://twgljs.org/dist/4.x/twgl.min.js"></script>
<canvas id="c" width="400" height="400"></canvas>

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