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Sharky Extreme : December 17, 2004





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(NOTE: The Permedia3-based 3Dlabs Create! board has an estimated ship date of July 30, 1999 so it can be classed as a late entry into the current generation of graphics chips or an early entry into the next, either way, you can't go out and buy it as of our publication date. - ED)

TNT performs single pass emboss bump mapping with two texture stage operations. Permedia 3 uses three texture stage operations, the additional texture stage being to blend the interpolated diffuse color with texture color. Without this additional stage, highlights tend toward white, instead of increased intensities of the diffuse color. This may suggest TNT is limited to two texture stage operations in a single pass, although word has it that the latest TNT drivers export an eight stage blending pipeline. However, to enable the eight stage interface would require some programming dexterity as the programming model is no longer that of a traditional DirectX cascade.

The existence of an eight-stage pipeline was confirmed by Derek Perez of NVIDIA:

"The 8 stage pipeline allows direct control of the TNT texture combiners and was implemented in v1.7x and newer driver. This is a new feature that allows developers to create any effect the TNT or TNT2 can do, including emboss bump mapping. The TNT/TNT2 core is capable of any kind of emboss bump mapping - the example we published happened to use white specular light, but other effects are possible."
The procedural texture mapping method generates low bandwidth natural textures on the fly. The water, torch flames, fire, shield belt effects that one sees in the game 'Unreal' all make use of procedural textures. TNT, like most modern graphic processors, 'swizzle' texture data. 'Swizzling' is a per-texel reorganization of texture data to make it cache friendly. However, unlike the Matrox G400 and the 3D Labs Permedia 3, the TNT pipeline textures exclusively using 'swizzled' data. It is unable to texture using intact, 'unswizzled' data. Because of this, the more intuitive way of applying procedural textures is not possible on TNT processors. Suffice to say that the technique of procedural texturing on TNT is a bit more involved and involves more system memory transfers.





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