LOSTCIRCUITS

Vertex skinning

Traditionally, most 3D animations have used a mesh of vertices to generate surfaces. In this case, each frame has to be generated by the CPU and transferred to the graphics adapter to be overlaid with the correct texture. This kind of animation, while very precise, requires a rather substantial amount of data transfer. A newer technique is called vertex skinning where the position of skeletal elements is combined with the movement and weighting of each element. Matrix operations carried out within the graphics engine are then used to generate a smooth transition between the individual components, that is, instead of showing broken bones a joint is created. Each bone in this case requires a separate matrix and the matrices are then blended into each other according to the weighting parameters assigned to each bone. The Charisma engine can hardware-accelerate four vertices without using CPU power.

Vertex Morphing is another term for keyframe interpolation. Keyframes are points in a specific sequence that are hard-coded. The more keyframes are used, the smoother is the transformation from one frame to the next. Needless to say that also in this case, the data transfer increases proportionally with the number of frames that are loaded. However, depending on the of the graphics engine, it is possible to interpolate between keyframes to generate a smooth transition from one to the other. A neat trick is that the number of intermittent or morphing frames can be adjusted by the application to account for complexity. That is, if applications start to slow down, the number of intermittent frames can be reduced to gain speed, naturally, this occurs at the expense of image quality. However for most applications the loss of quality will be relatively minor since the human eye and brain use exactly the same principle to generate smooth transitions between natural keyframes. Hardware acceleration of keyframe interpolation is another novum of the Charisma engine.

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