Learn antialiasing techniques in computer graphics (Part 3)

(Adaptive AA AMD)
As noted in section 2, MSAA antialiasing solution is quite good, it offers picture quality good performance along with good handling, but MSAA has a significant drawback is that it can not handle aliasing for object surface remains transparent (transparency texture). So developers have to do to eliminate aliasing of this? Proceed to the third track of the types of articles, "Understanding antialiasing techniques in computer graphics" immediately following:


First, we will learn about Van transparent.
The game now contains many of the complex 3-dimensional objects, each object composed of many polygons (polygons), each polygon contains as much information of the object so that light, shadows ... So developers have to "draw" available models of detail from high to low depending on the distance of the object to the player to reduce the load to the system. Tessellation Technology in libraries such as DirectX 11 part 1 in this article has solved this problem.

But when so many small but complex objects appear together in a scene then stars (eg many leaves in the forest, or a lawn, or on a grid mesh ...). If each individual mesh is not built a computer that can afford huge number of such objects, including the most powerful gaming machine today. Van transparent solution to this problem.


Van transparent to simulate complex discrete objects which by conventional 2D images. Let's take a concrete example B40 mesh fence in the game. Instead of building each separate mesh, only the "draw" a complete 2D grid array, and do throughout the mesh in the middle, so we had a very nice grade mesh fence but did not do heavy machine.

following photos will give you the figure is still over how, the geometric objects and show how the final scene in Star game:

of the barrier layer remains (the cell backgrounds are transparent layer board)
frame model of the 3D object behind the Picture
mesh is created as when combining two layers on
As you can see, still during the problem solved to show the details of this mesh without increasing the system load. But still a major problem in class during this, because MSAA, as mentioned above, can not be de-aliasing for so transparent, so the mesh remains intact whether you have aliasing turned on 16X MSAA matter. SSAA is serrated for handling this mesh very well, but then re-shuffling speed dramatically. Hence arose that required a new technique for handling the remains during this class.


NVIDIA has its own technology to do this. With the publication of the GeForce 7 series (launched in June / 2005 - this product is the most powerful GeForce 7950), they have introduced an anti-aliasing techniques to remain transparent, referred to as TAAA. TAAA 2 approach, a technique using MSAA (called TrMSAA - Transparency MSAA) and a use SSAA (called TrSSAA - Transparency SSAA).

Earlier there was talk principles of MSAA is to handle the pixel located at the edges of objects. With TAAA, the pixel is in transparent objects will still be sampled, not just the next pixel. Two different techniques of TAAA is: TrMSAA pixel will sample the fringes during the MSAA sample, while samples for TrSSAA will remain throughout the 2, 4 or 8 samples, separately for the pixels at the edges . Everything seems to be solved completely.

TrMSAA and NVIDIA TrSSAA
But not really. In theory, as on every pixel has been handled. But TrSSAA not play with DirectX 9, TrMSAA also works with DirectX 9, but not stable.

Side AMD also developed a technique similar to Nvidia's TAAA, called ADAA ( Adaptive AA - Adaptive antialiasing), along with the Radeon X1000 card (ATi then was). Operating principle similar TAAA, only difference is that ATi limited processing techniques MSAA so transparent, that is exactly like the TrMSAA, including works with DirectX 9. ADAA ATi said this technique can still use their game with DirectX 10 and 11, if the developer to apply this technique to their game. There are currently some game ADAA applied, for example STALKER: Clear Sky, STALKER: Call of Pripyat and Metro 2033 was effective application of this technique.


Comparison of treatment performance of the GeForce 2 and Radeon

See the image above you can see, aliasing techniques for handling still surface provides superior image quality. The grille has become smooth and smooth, unlike the bad results that bring traditional MSAA.

However, the game with DirectX 10 and 11, why? In DirectX 10 and 11 has a technology called alpha-to-coverage, using the power of the GPU to handle the remains jagged surface. The new game in 2012 this has applied the technique of rendering good fences and trees and less jagged than the generation DirectX 9 games. Next article will explain the new antialiasing techniques in DirectX 10 and 11.


TomsHardware References (continued)