9.0

164 FORCE FIELDS
DYNAMICS
DYNAMICS
FORCE FIELDS 165
Note that occasionally paradoxical situations may arise, such as motion that heads
into the wind. In such cases you should reduce the Lift Coeff. in one of two places,
either in the Wind settings or the Rigid Body Dynamic settings. The latter is usually
preferable since it enables you to adjust the lift for a deviant object without affecting
the ight of other objects.
Linear Coeff., Angular Coeff.
These two settings relate to linear velocity and angular velocity, which both play a
part in an object’s motion in the wind eld. However, it is not just the wind’s velocity
that needs to be taken into account, but the object’s velocity also.
The velocity will affect an
object’s behavior in wind. The
effective velocity that will be
considered is the sum of the
wind’s velocity and the object’s
velocity.
Although Linear Coeff. and Angular Coeff. are set to 100% by default, you will need
to set values for the Linear and Angular parameters in the Rigid Body Dynamic Tag
if you want the velocity to be taken into account. This is because Linear and Angular
in the Rigid Body Dynamic Tag are set to 0 (i.e. disabled) by default. In general, leave
the parameters in the Wind settings set to 100%, but set their counterparts in the
Rigid Body Dynamic Tag to values between 1% and 10% for a realistic result.
Example 1
An aeroplane is taking off at 100 km/h, heading into a wind of 50 km/h. The relative
wind velocity that affects the wing’s surface is 150 km/h.
Example 2
A plane is taking of at 100 km/h with a following wind of 50 km/h. Hence the relative
wind velocity is just 50 km/h. This highlights the reason why aeroplanes will take off
from various runways according to the direction of the wind.
Linear Coeff. denes the strength of this effect for linear motion, whereas Angular
Coeff. denes the strength of the effect for angular motion. To switch off the linear
of angular effect, set the corresponding parameter to 0.