Alpha to Coverage

Alpha to coverage is an anti -aliasing technology that enables alpha blending textures such as fences or vegetation to render.

Introduction

Some of the textures in modern video games require alpha textures, as used for example in the representation of vegetation or fences. The normal anti-aliasing, also called edge antialiasing can not be used for alpha textures, so there is the problem of the edge fibrillation. This can be prevented only with transparent anti-aliasing. One way of transparent antialiasing was previously supersampling ( SSAA ), but this is considered extremely computationally heavy. There are also output recorded and scaled textures here in the sense of full-screen anti-aliasing, short FSAA, the texture quality is increased.

The alpha -to- coverage allows the anti-aliasing to detect this alpha - smooth textures and a relatively high speed. In addition, there is the problem that most modern games use off-screen buffer and thus AA is more difficult.

Technology

This method uses the alpha channel of textures as a coverage mask for anti-aliasing. Alpha to Coverage multisampling is based on regular multisampling except that the alpha coverage mask is linked to the multisample mask. Alpha to Coverage converts the alpha component output from the pixel shader to a coverage mask. If multisampling is used, each output fragment receives a transparency of 0 or 1, depending on the Alpha Coverage and multisampling result.