The Radeon 256 marks a new move for ATI, and with this step, they have chosen the path of NVIDIA, believing that the future lies in Hardware T&L and not entirely in the cinematic effects boasted by 3dfx’s Voodoo5.
The Radeon name will be used by ATI from this point forward for all of their chips that feature their “Charisma Engine,” which is their Hardware Transform, Clipping & Lighting Engine.
The Charisma Engine handles much more than NVIDIA’s Hardware T&L engine does because, in addition to performing transforming and lighting calculations on the chip, the engine also allows for clipping operations as well as two interesting features, vertex skinning and keyframe interpolation, to be performed on-chip instead of offloading those calculations onto the host CPU.
Vertex skinning allows for more realistic bending/moving of polygons in games that use skeletal animation so that characters appear to move more realistically than the blocky motion we’re used to. The perfect example would be Half Life, which uses skeletal animation; unfortunately vertex skinning isn’t supported by the engine.
Keyframe interpolation is another animation acceleration feature that takes the starting and ending frames of an animation and, by measuring the changes in the two frames, can interpolate intermediate frames so that you don’t to generate as many frames for a single animation.