Multisample Antialiasing

MSAA is the default mode and it is implemented by the GPU. Most modern GPUs are capable of this form of antialiasing. In multisample antialiasing, each pixel at the edge of a polygon is sampled multiple times. For each sample-pass, a slight offset is applied to all screen coordinates. This offset is smaller than the actual size of the pixels. By averaging all these samples, the result is a smoother transition of the colors at the edges.

Noesis Views always display content in the active render target. Just binding a render target with MSAA enabled will render the UI with antialiasing enabled. Our Application Framework supports enabling MSAA by using the command line switch '--samples N'.

In case you also want MSAA in the offscreens, you need to indicate the number of samples before initializing each View in the render thread.

Ptr<GLRenderDevice> device = *new GLRenderDevice();
device->SetOffscreenSampleCount(8);

view->GetRenderer()->Init(device);

Per-Primitive Antialiasing

For cases where MSAA cannot be used or it is expensive, Noesis provides a cheap solution that extrudes the contours of the geometry and smooths them using alpha blending.

PPAA can be enabled in a view by activating the flag 'RenderFlags_PPAA'.

view->SetFlags(Noesis::RenderFlags_PPAA);

This will enable PPAA globally for the view. PPAA can also be selectively disabled per node by using the extended XAML property PPAAMode. PPAA generates extra geometry so in cases where PPAA is not needed, for example when using a rectangle that is never rotated, it is a good idea to disable PPAA to save bandwidth.

There is also two extended XAML properties to control how the extrusion happens, PPAAIn and PPAAOut. The first one indicates how many pixels the geometry is shrunk and the second one indicates how many pixels vertices are extruded out. Between the PPAAIn and PPAAOut area, alpha transitions from 1.0 to 0.0. The default values are quite conservative to avoid glitches but depending on the geometry they can be increased to improve the antialiasing result.

PPAAMode, PPAAIn and PPAAOut are inherited properties that are propagated down the tree. Remark here that setting PPAAMode to Disabled in View's Content element won't disable PPAA for Popups and ToolTips as those are placed on another visual layer and are not children of Content element.

<Canvas
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:noesis="clr-namespace:NoesisGUIExtensions;assembly=Noesis.GUI.Extensions"
  Background="White">

  <StackPanel Orientation="Horizontal">
    <Rectangle noesis:Element.PPAAMode="Disabled" Fill="Black" Width="100" Height="100">
      <Rectangle.RenderTransform>
        <TransformGroup>
          <RotateTransform Angle="60"/>
          <TranslateTransform X="100" Y="10"/>
        </TransformGroup>
      </Rectangle.RenderTransform>
    </Rectangle>
    <Rectangle noesis:Element.PPAAMode="Default" Fill="Black" Width="100" Height="100">
      <Rectangle.RenderTransform>
        <TransformGroup>
          <RotateTransform Angle="60"/>
          <TranslateTransform X="150" Y="10"/>
        </TransformGroup>
      </Rectangle.RenderTransform>
    </Rectangle>
    <Rectangle noesis:Element.PPAAIn="1" noesis:Element.PPAAOut="1" Fill="Black" Width="100" Height="100">
      <Rectangle.RenderTransform>
        <TransformGroup>
          <RotateTransform Angle="60"/>
          <TranslateTransform X="200" Y="10"/>
        </TransformGroup>
      </Rectangle.RenderTransform>
    </Rectangle>
  </StackPanel>
</Canvas>