Game Development Reference
In-Depth Information
7 Setting up a single
mesh character
If your character was a jointed robot then you could set it up so that each
individual part that moves is a separate object. Then you will need some
way of informing your transformation code that a bicep is connected to a
shoulder, a forearm is connected to the bicep and a hand is connected to
the forearm. In this chapter we will consider how you can set up
hierarchies of objects so that rotating and transforming the object will
affect not only the object itself, but also those other objects that are
connected to it. But we need to go further than this; we want to be able to
deform a character so that the rendered result will appear as a single
mesh. If we attempt to display an organic character using separate
objects for each section, the result will either appear as though the
sections overlap, or that the sections appear to be separated. To display
organic characters effectively in your real-time render engine, we need to
be able to move certain vertices in a mesh and not others.
Whatever deformation system we use we need to be able to rotate and
transform a section of a mesh using some form of control object. There
are several ways in which this can be achieved; this chapter looks at
some possible methods. One method described takes a complete mesh
that is the render target, and then uses sections cut from the object as
controls. These controls will affect how the animation engine deforms the
full mesh. The render engine will not display the controls, just the full
mesh. Before we consider this option we will look at the leading
alternative method, bones, and discuss why some implementations of
bones have severe performance penalties when applied to real-time
rendering engines. We will consider how we can implement a bones-
based system using control objects, which can be readily imported from
key modelling software. We will consider hierarchies of objects where the
parent of an object affects its animation. Finally, as hardware develops
apace we will look at how the single mesh deformations we are
considering are suitable for real-time rendering systems that use some
form of subdivision.
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