A new physics model is being developed for the virtual gliding game. This models forces based on airspeed and sink rate independent of changes in the position over the ground. This incorporates the effects of wind, which is not included in the standard Unity3d physics system.
When gliding through the air, the airspeed or sink rate of the glider is relative to the air it is flying through. It has nothing to do with the speed over, or rate it approaches, the ground. Unfortunately, the standard Unity3d physics engine measures velocities based on changes in position over the ground and is unsuitable for a virtual gliding game.
The system being developed will allow an object to glide with a constant airspeed and sink rate through the air it is travelling through. If wind, lift from a thermal, or sink, causes that air to also move, the glider speed and sink rate relative to the ground could and probably will be very different. As an example:
If the wind is 50kph and a glider has an airspeed of 100kph, its downwind speed over the ground would be 150kph. Its speed upwind over the ground would be 50kph.
If a glider with a sink rate of 1m/s is flying through an air rising at 2m/s, then the glider would gain height at 1m/s.
With the standard Unity physics model, you would normally ‘add an extra force’ to account for the wind, however the aircraft is travelling with the wind and therefore does not accelerate, so no force is applied by the wind. The new physics model takes this into account.