Game Development Reference
In-Depth Information
Modeling
Although we've yet to cover a lot of the material required to implement a real-time flight
simulator, we'd like to go ahead and outline some of the steps necessary to calculate the
lift and drag forces on your model aircraft:
1. Discretize the lifting surfaces into a number of smaller wing sections.
2. Collect geometric and foil performance data.
3. Calculate the relative air velocity over each wing section.
4. Calculate the attack angle for each wing section.
5. Determine the appropriate lift and drag coefficients and calculate lift and drag
forces.
The first step is relatively straightforward in that you need to divide the aircraft into
smaller sections where each section is approximately uniform in characteristics. Per‐
forming this step for the model shown in Figure 15-2 , you might divide the wing into
four sections—one for each wing section that's fitted with an aileron and one for each
section that's fitted with a flap. You could also use two sections to model the elevators,
one port and one starboard, and another section to model the tail/rudder. Finally, you
could lump the entire fuselage together as one additional section or further subdivide
it into smaller sections depending on how detailed you want to get.
If you're going to model your aircraft as a rigid body, you'll have to account for all of
the forces and moments acting on the aircraft while it is in flight. Since the aircraft is
composed of a number of different components, each contributing to the total lift and
drag, you'll have to break up your calculations into a number of smaller chunks and
then sum all contributions to get the resultant lift and drag forces. You can then use
these resultant forces along with thrust and gravity in the equations of motion for your
aircraft. You can, of course, refine your model further by adding more components for
such items as the cockpit canopy, landing gear, external fuel pods, bombs, etc. The level
of detail to which you go depends on the degree of accuracy you're going for. If you are
trying to mimic the flight performance of a specific aircraft, then you need to sharpen
your pencil.
Once you've defined each section, you must now prepare the appropriate geometric and
performance data. For example, for the wings and other lifting surfaces you'll need to
determine each section's initial incidence angle (its fixed pitch or attack angle relative
to the aircraft reference system), span, chord length, aspect ratio, planform area, and
quarter-chord location relative to the aircraft's center of gravity. You'll also have to pre‐
pare a table of lift and drag coefficients versus attack angle appropriate for the section
under consideration. Since this data is usually presented in graphical form, you'll have
to pull data from the charts to build your lookup table for use in your game. Finally,
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