drawing our focus to
be on the generalities of rigging for real-time gaming.
The first general concept of real-time rendering for games is the notion of run-time performance. Due to games running in real-time,
the more skinned polygons and joints, as well as all of the other
components that need to be rendered, the more time it takes to render, and therefore the slower the frame rate of the game. Generally speaking, most games run at 30 or 60 Hz (frames per second).
This immediately enforces the need for determining and adhering
to budgets for the number of joints in a skeleton hierarchy and the
number of skinned vertices weighted to them. Of course, there are
a number of other art components that affect run-time performance,
but we will leave them outside of the scope of this course in order
to focus on digital character rigging.
Still, measuring the performance impact solely on the number of
joints and skinned vertices is only part of the picture. The manner
in which those vertices are skinned to the joints also affects performance. Depending on the hardware, or rendering system, the number of joint influences that each vertex can be weighted to may have
a significant performance impact. Generally speaking, Xbox360
and PS3 hardware performs optimally when each vertex is limited
to a maximum of four joint influences. Hardware in the range of
PS2 or Wii range generally performs optimally with a maximum
of three joint influences. Mobile can be as low as one or two joint
influences