THREE.EffectComposer = function ( renderer, renderTarget ) {
//这里初始化renderer和renderTarget没啥说的
  this.renderer = renderer;

  if ( renderTarget === undefined ) {

    var parameters = {
      minFilter: THREE.LinearFilter,
      magFilter: THREE.LinearFilter,
      format: THREE.RGBAFormat,
      stencilBuffer: false
    };

    var size = renderer.getDrawingBufferSize();
    renderTarget = new THREE.WebGLRenderTarget( size.width, size.height, parameters );
    renderTarget.texture.name = 'EffectComposer.rt1';

  }

  this.renderTarget1 = renderTarget;
  this.renderTarget2 = renderTarget.clone();
  this.renderTarget2.texture.name = 'EffectComposer.rt2';

  this.writeBuffer = this.renderTarget1;//到这里write read都是来自传入的renderTarget或者创建的新的那个
  this.readBuffer = this.renderTarget2;

  this.passes = [];//装所有PASS的

  // dependencies

  if ( THREE.CopyShader === undefined ) {

    console.error( 'THREE.EffectComposer relies on THREE.CopyShader' );

  }

  if ( THREE.ShaderPass === undefined ) {

    console.error( 'THREE.EffectComposer relies on THREE.ShaderPass' );

  }

  this.copyPass = new THREE.ShaderPass( THREE.CopyShader );

};

Object.assign( THREE.EffectComposer.prototype, {

  swapBuffers: function () {//双缓冲用的

    var tmp = this.readBuffer;
    this.readBuffer = this.writeBuffer;
    this.writeBuffer = tmp;

  },

  addPass: function ( pass ) {

    this.passes.push( pass );//增加pass

    var size = this.renderer.getDrawingBufferSize();
    pass.setSize( size.width, size.height );

  },

  insertPass: function ( pass, index ) {//给pass换个顺序

    this.passes.splice( index, 0, pass );

  },

  render: function ( delta ) {

    var maskActive = false;

    var pass, i, il = this.passes.length;

    for ( i = 0; i < il; i ++ ) {//遍历所有pass

      pass = this.passes[ i ];

      if ( pass.enabled === false ) continue;//不用这个pass就过

      pass.render( this.renderer, this.writeBuffer, this.readBuffer, delta, maskActive );
      //这个render就要看看那个pass里面咋写的了 一般是renderer readBuffer这俩参数传入渲完再给writeBuffer
      //有的是用readBuffer渲完了继续给readBuffer覆盖了原来的readBuffer

      if ( pass.needsSwap ) {

        if ( maskActive ) {

          var context = this.renderer.context;

          context.stencilFunc( context.NOTEQUAL, 1, 0xffffffff );//模板测试

          this.copyPass.render( this.renderer, this.writeBuffer, this.readBuffer, delta );

          context.stencilFunc( context.EQUAL, 1, 0xffffffff );

        }

        this.swapBuffers();

      }

      if ( THREE.MaskPass !== undefined ) {

        if ( pass instanceof THREE.MaskPass ) {

          maskActive = true;

        } else if ( pass instanceof THREE.ClearMaskPass ) {

          maskActive = false;

        }

      }

    }

  },

  reset: function ( renderTarget ) {

    if ( renderTarget === undefined ) {

      var size = this.renderer.getDrawingBufferSize();

      renderTarget = this.renderTarget1.clone();
      renderTarget.setSize( size.width, size.height );

    }

    this.renderTarget1.dispose();
    this.renderTarget2.dispose();
    this.renderTarget1 = renderTarget;
    this.renderTarget2 = renderTarget.clone();

    this.writeBuffer = this.renderTarget1;
    this.readBuffer = this.renderTarget2;

  },

  setSize: function ( width, height ) {

    this.renderTarget1.setSize( width, height );
    this.renderTarget2.setSize( width, height );

    for ( var i = 0; i < this.passes.length; i ++ ) {

      this.passes[ i ].setSize( width, height );

    }

  }

} );


THREE.Pass = function () {

  // if set to true, the pass is processed by the composer
  this.enabled = true;

  // if set to true, the pass indicates to swap read and write buffer after rendering
  this.needsSwap = true;

  // if set to true, the pass clears its buffer before rendering
  this.clear = false;

  // if set to true, the result of the pass is rendered to screen
  this.renderToScreen = false;

};

Object.assign( THREE.Pass.prototype, {

  setSize: function ( width, height ) {},

  render: function ( renderer, writeBuffer, readBuffer, delta, maskActive ) {

    console.error( 'THREE.Pass: .render() must be implemented in derived pass.' );

  }

} );