QMultiSampleAntiAliasing Class

Detailed Description

Enable multisample antialiasing

A Qt3DRender::QMultiSampleAntiAliasing class enables multisample antialiasing.

It can be added to a QRenderPass by calling QRenderPass::addRenderState():

  QRenderPass *renderPass = new QRenderPass();

  QMultiSampleAntiAliasing *msaa = new QMultiSampleAntiAliasing();
  renderPass->addRenderState(msaa);

Or a QRenderStateSet by calling QRenderStateSet::addRenderState():

  QRenderStateSet *renderStateSet = new QRenderStateSet();

  QMultiSampleAntiAliasing *msaa = new QMultiSampleAntiAliasing();
  renderStateSet->addRenderState(msaa);

For multisampling to take effect, the render target must have been allocated with multisampling enabled:

  QTexture2DMultisample *colorTex = new QTexture2DMultisample;
  colorTex->setFormat(QAbstractTexture::RGBA8_UNorm);
  colorTex->setWidth(1024);
  colorTex->setHeight(1024);

  QRenderTargetOutput *color = new QRenderTargetOutput;
  color->setAttachmentPoint(QRenderTargetOutput::Color0);
  color->setTexture(colorTex);

  QTexture2DMultisample *depthStencilTex = new QTexture2DMultisample;
  depthStencilTex->setFormat(QAbstractTexture::RGBA8_UNorm);
  depthStencilTex->setWidth(1024);
  depthStencilTex->setHeight(1024);

  QRenderTargetOutput *depthStencil = new QRenderTargetOutput;
  depthStencil->setAttachmentPoint(QRenderTargetOutput::DepthStencil);
  depthStencil->setTexture(depthStencilTex);

  Qt3DRender::QRenderTarget *renderTarget = new Qt3DRender::QRenderTarget;
  renderTarget->addOutput(color);
  renderTarget->addOutput(depthStencil);

Further, the shader code must use multisampling sampler types and texelFetch() instead of texture().

For example, if you have code like

  #version 150

  uniform sampler2D colorTexture;
  in vec2 texCoord;
  out vec4 fragColor;

  void main()
  {
      fragColor = texture(colorTexture, texCoord);
  }

you can rewrite it as

  #version 150

  uniform sampler2DMS colorTexture;
  in vec2 texCoord;
  out vec4 fragColor;

  void main()
  {
      ivec2 tc = ivec2(floor(textureSize(colorTexture) * texCoord));
      vec4 c = texelFetch(colorTexture, tc, 0) +
                  texelFetch(colorTexture, tc, 1) +
                  texelFetch(colorTexture, tc, 2) +
                  texelFetch(colorTexture, tc, 3);
      fragColor = c / 4.0;
  }

Note: When using OpenGL as the graphics API, glEnable(GL_MULTISAMPLE) will be called if QMultiSampleAntiAliasing has been added to the render states.