Overview

V4 中改变全局状态的唯一途径就是通过 Renderer 对象。如开启深度测试。接下来将逐一分析如何通过 Renderer 设置全局状态及固定管线函数。

clear attachment

通过 ClearFlag 指定需要清空的缓冲区

_renderer->clear(ClearFlag::ALL, // Clear color, depth and stencil buffer. 
                _clearColor,     // the color value used when the color buffer is cleared
                1, // the depth value used when the depth buffer is cleared 
                0, // the index used when the stencil buffer is cleared 
                -10000.0); // specifies the globalOrder value

深度测试

在初始化函数中，设置回调函数，用于保存和恢复原先的全局状态。

void Demo::init()
{
    _customCommand.setBeforeCallback(CC_CALLBACK_0(Demo::onBeforeDraw, this));
    _customCommand.setAfterCallback(CC_CALLBACK_0(Demo::onAfterDraw, this));
}

• onBeforeDraw

  void Demo::onBeforeDraw()
  {
      auto renderer = Director::getInstance()->getRenderer();
      // manually save the global state
        _oldDepthTestEnabled = renderer->getDepthTest();
        _oldDepthWriteMask = renderer->getDepthWrite();
        _oldDepthCmpFunc = renderer->getDepthCompareFunction();
        ... //store other global state, such as cull mode.
      renderer->setDepthTest(true);
        renderer->setDepthWrite(true);
        renderer->setDepthCompareFunction(backend::CompareFunction::LESS_EQUAL);
        ... //do additional operations.
  }
  

• onAfterDraw

  void Demo::onAfterDraw()
  {
      auto renderer = Director::getInstance()->getRenderer();
           // manually restore the global state
        renderer->setDepthTest(_oldDepthTestEnabled);
        renderer->setDepthWrite(_oldDepthWriteMask);
        renderer->setDepthCompareFunction(_oldDepthCmpFunc);
        ... //restore other global state
  }
  

模板测试

与深度测试一样，设置用于保存和恢复原先全局状态的回调函数。

void Demo::init()
{
    _customCommand.setBeforeCallback(CC_CALLBACK_0(Demo::onBeforeDraw, this));
    _customCommand.setAfterCallback(CC_CALLBACK_0(Demo::onAfterDraw, this));
}

• onBeforeDraw

  void Demo::onBeforeDraw()
  {
      auto renderer = Director::getInstance()->getRenderer();
      // manually save the stencil state
      _oldStencilEnabled = renderer->getStencilTest();
      _oldStencilWriteMask = renderer->getStencilWriteMask();
      _oldStencilFunc = renderer->getStencilCompareFunction();
      _oldStencilRef = renderer->getStencilReferenceValue();
      _oldStencilReadMask = renderer->getStencilReadMask();
      _oldStencilFail = renderer->getStencilFailureOperation();
      _oldStencilPassDepthFail = renderer->getStencilPassDepthFailureOperation();
      _oldStencilPassDepthPass = renderer->getStencilDepthPassOperation();
        ... // save other global states
  
      // set stencil states
      renderer->setStencilTest(true);
      renderer->setStencilWriteMask(_writeMask);
      renderer->setStencilCompareFunction(_compareFunction, 
                                          _refValue, 
                                          _readMask);
      renderer->setStencilOperation(_sfailOp,
                                    _zfailOp, 
                                    _zpassOp);
  }
  

• onAfterDraw

  void StencilStateManager::onAfterVisit()
  {
      // manually restore the stencil state
      auto renderer = Director::getInstance()->getRenderer();
      renderer->setStencilCompareFunction(_oldStencilFunc, 
                                          _oldStencilRef, 
                                          _oldStencilReadMask);
  
      renderer->setStencilOperation(_oldFail, 
                                    _oldPassDepthFail,
                                    _oldPassDepthPass);
  
      renderer->setStencilWriteMask(_oldStencilWriteMask);
      if (!_oldStencilEnabled)
      {
          renderer->setStencilTest(false);
      }
  }
  

Viewport

//保存当前 viewport
_oldViewport = renderer->getViewport(); 
renderer->setViewPort(viewport.origin.x, 
                      viewport.origin.y, 
                      viewport.size.width, 
                      viewport.size.height);

Scissor

//save scissor test status
_oldScissorTest = renderer->getScissorTest();
_oldScissorRect = renderer->getScissorRect();

//set scissor test
renderer->setScissorTest(true);
renderer->setScissorRect(x, y, width, height);

//restore scissor test status
renderer->setScissorTest(_oldScissorTest);
renderer->setScissorRect(_oldScissorRect.x, 
                         _oldScissorRect.y, 
                         _oldScissorRect.width, 
                         _oldScissorRect.height);

CullMode

_oldCullMode = renderer->getCullMode();
renderer->setCullMode(cullMode);

Winding

_oldWinding = renderer->getWinding();
renderer->setWinding(winding);

Set render target

设置用于保存和恢复 attachment 的回调函数。

void Demo::init()
{
      _beginCallbackCommand.func = CC_CALLBACK_0(RenderTexture::onBegin, this);
    _endCallbackCommand.func = CC_CALLBACK_0(RenderTexture::onEnd, this);
}

• onBegin

  //save attachemnt status
  _oldColorAttachment = renderer->getColorAttachment();
  _oldDepthAttachment = renderer->getDepthAttachment();
  _oldStencilAttachment = renderer->getStencilAttachment();
  _oldRenderTargetFlag = renderer->getRenderTargetFlag();
  
  renderer->setRenderTarget(_renderTargetFlags, // indicate which attachment to be replaced 
                            _texture2D, 
                            _depthTexture, 
                            _stencilTexture);
  

• onEnd

  renderer->setRenderTarget(_oldRenderTargetFlag, 
                            _oldColorAttachment, 
                            _oldDepthAttachment, 
                            _oldStencilAttachment);