Game Development Reference

In-Depth Information

Right Shoulder

Right Bicep

Right Forearm

Right Wrist

Right Hand

Left Thigh

Left Calf

Left Ankle

Left Foot

Left Toe

Right Thigh

Right Calf

Right Ankle

Right Foot

Right Toe

In this hierarchy there are 25 possible bones. In a simple low polygon

single mesh character you may have 1000 vertices. If each of these 1000

vertices is acted on by 25 bones, then there are 25 000 calculations to

perform rather than just 1000. This is 25 times as many calculations to do

than we would prefer. Our real-time engine needs much more focus over

which vertices are deformed by which bone. But, suppose that no vertex

is acted on by more than one bone. This can lead to some very unwanted

artefacts. Let's consider how the mesh at a knee joint may behave if each

vertex in the mesh is controlled by a single bone. As the joint rotates, the

vertices at the back of the knee that influence the calf can end up

overlapping the vertices for the thigh (see Figure 7.1). This can lead to

very bad nipping. At a distance this may be acceptable, but close up to

Figure 7.1 How vertex selection can result in poor quality rendering.

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