C. Part Selection
OpenGL supports mouse picking, which identifies the
object over which a mouse pointer hovers; however,
OpenGL ES for embedded systems including the iPhone
does not support it. We cope with this limitation by assigning
colors to 3D model parts as additional data, as depicted in
Fig. 6. The color added is called a proxy color and assigned
independently from the color of the original model part. For
example, the color of red may be assigned to a head part by
the system arbitrarily so that the part can be separated from
others. Assignment of the proxy colors is performed when
the associated X file is loaded into the system.