DirectX 10 features and technical details (10), (alpha to coverage effect)

Other improvements to DirectX 10

Alpha to coverage

In games, polygon models with translucent information textures are often used to simulate complex objects, such as grass, leaves, and barbed wire. If you use a real model, a grass with uneven edges may consume hundreds of polygon. However, with transparent textures, you can use only 2 ~ Three polygon are solved.

Transparent texture Diagram

However, when this translucent texture is used, its border line between opacity and transparency is often ugly. Semi-transparent hybrid technology can solve this problem, but it needs to draw all such objects in the scene from far to near order, in order to ensure that their occlusion relationship is correct, this puts a lot of pressure on the CPU and is not desirable. In earlier versions of DirectX, Alpha testing and mixing are simply a nightmare for graphic programmers.

In DirectX 10, a new technology called Alpha to coverage is used. Using this technology, texture pixels at the junction of transparency and opacity are sampled in Multi-sample mode to achieve anti-aliasing. This solves this problem simply and effectively without introducing high performance overhead. Games in outdoor scenarios will greatly benefit from this technology, and the edge of leaves, barbed wire, and grass will be softer and smoother.

Alpha to coverage Effect

Shadow Map Filtering

Shadow Map has gradually become a popular technology for rendering realistic shadows. It can be seen in the next generation of games including war machine, split cell: Dual agents, Ghost Recon, and Assassin's Creed. However, due to the size limitation of the shadow map, the shadow edges implemented by the shadow map often have obvious serrations. In DirectX 10, the shadow map filtering function is officially supported. After filtering, the edge of the Shadow will become softer.

 

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