As is described in the previous chapter, after the intention generator
chooses an intention, it invokes the focusser. For example, when the
avoid intention is generated, the perception focusser is
activated to locate the positions of the obstacles, paying special
attention to the most dangerous one. To enable the choice of
favorable actions, the focusser must compute motor preferences in
accordance with the environmental conditions (see
Section. 
for details). This process requires the
availability of 
--the strength of the desire from which a motor
preference was assigned a value. In the current implementation, motor
preferences may be derived from four desires: avoid (collision), fear,
eat and mate.
Let 
, 
, 
and 
denote the
strength of these four desires, respectively. Their values are
given by:
where 
( 
) is the strength of the current
intention and if 
, 
.
Once the focusser has computed and collected all the motor preferences, it passes only information about the geometry, positions, and/or velocities of the attended object along with these preferences to the appropriate behavior routine.
| Xiaoyuan Tu | January 1996 |