| What is a shader ? |
| What do we need to render a three dimensional object; 2D on your monitor? We start off by building some sort of structure that has a surface, that surface is being built from triangles and why triangles? They are quick to calculate. How's each triangle being processed? Each triangle has to be transformed according to its relative position and orientation to the viewer. Each of the three vertices the triangle is made up of is transformed to its proper view space position. The next step is to light the triangle by taking the transformed vertices and applying a lighting calculation for every light defined in the scene. At last the triangle needs to be projected to the screen in order to rasterize it. During rasterization the triangle will be shaded and textured.
Graphic processors like the GeForce and Radeon series are able to perform a certain amount of these tasks. The first generation was able to draw shaded and textured triangles in hardware. The CPU still had the burden to feed the graphics processor with transformed and lit vertices, triangle gradients for shading and texturing, etc. Integrating the triangle setup into the chip logic was the next step and finally even transformation and lighting (TnL) was possible in hardware, reducing the CPU load considerably. The big disadvantage was that a game programmer had no direct (i.e. program driven) control over transformation, lighting and pixel rendering because all the calculation models were fixed on the chip. And now we finally get to the stage where we can explain Shaders. Vertex and Pixel shaders allow developers to code customized transformation and lighting calculations as well as pixel coloring functionality. Each shader is basically nothing more than a relatively small program executed on the graphics processor to control either vertex or pixel processing. |
It has been widely discussed and argumented, ATI listened and did decide to implement SM3 into the new architecture. A good call of course, SM3 allows the programmer to fire off some very nice shader programs that in certain cases can speed up your game. The world has moved on to SM3, people expect it to be integrated and so it has and had to be been done. Very good integration I might add because SM3 seems to work pretty darn efficiently for ATI, it has to do with dynamic branching, that matter is too far fetched to explain for this article to get into. What you need to know is that it works really well. More efficiency that really is what the new card is all about. I'll be using that word in thus review a lot. According to the chip designers every transistor in that core is constantly put to use to push the results onto your screen, yes efficiency.
Another feature, and yeah it's not new to our ears at all, yet it had a little upgrade has to do with texture compression capabilities. Almost any, well any, graphics card nowadays makes use of texture compression technology. It's been discussed here on more then one occasion, I'm sure you recognize terms like S3TC and DXTC. Basically you reduce the byte-size of a texture while maintaining the best quality as possible. However, compression equals artifacts and thus image degradation at some point. 3Dc is a compression technology designed to bring out fine details in games while minimizing memory usage. It's the first compression technique optimized to work with normal maps, which allow fine per-pixel control over how light reflects from a textured surface. With up to 4:1 compression possible, this means game designers can now include up to 4x the detail without changing the amount of graphics memory required and without impacting performance.
3Dc was upgraded a little and on the X1000 series of cards we now have 3Dc+ available to us. Let me just get it out of the way and move on. High quality normal map compression can (and could) be handled up-to a 4:1 ratio and works on any two-channel texture format. This updated + edition adds support for single-channel textures with 2:1 compression, which is good enough for stuff like luminance maps, shadow maps, HDR textures and more.
At the ATI presentation it became obvious that ATI focused extremely hard on HDR, just like NVIDIA did. They put a lot of money into their technology to support HDR in the best possible way. And they should as it just is a fantastic effect that brings so much more to the your gameplay experience. HDR is something you all know from games like Far Cry, extremely bright lighting that brings a really cool cinematic effect to gaming. This effect is becoming extraordinarly popular. Valve (who it rather lazy in keeping their word when it comes to releases) is working on some HDR goodness in Half Life 2: Lost Coast also. This little update should have been released in August though. Anyway, the difference is obvious. HDR means High Dynamic Range. HDR facilitates the use of color values way beyond the normal range of the color palette in an effort to produce a more extreme form of lighting rendering. Typically this trick is used to contrast really dark scenery. Extreme sunlight, over-saturation or over exposure is a good example of what exactly is possible. The most simple way to describe it would be controlling the amount of light used present in a certain position in a 3D scene. HDR is already present in Far Cry, somewhere in our lifetime I hope, in Half Life 2: Lost Coast and will be available in Unreal 3 to name a few titles.
One last thing about HDR, ATI's HDR resolution can manage Antialiasing with HDR enabled, something that is not possible with the cards from the competition. The games need to be patched though, I expect one from CryTek soon!
Let's make some screenshots do the talking.
Look clearly at the overexposed lighting effects, that's HDR. It'll bring a nice cinematic effect to gaming. Mind you that these screenshots did not have AA disabled while with an upcoming Far Cry patch that will be possible.
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