Add the Thermal wind force

[NickolausDS]

A thermal is a bubble of warm air that coalesces on the ground and forms a column of rising air.

Emulate thermals so that flight objects can exploit them for free upward movement.

Requires #130

[corstian]

Would there be any change of creating thermals based on the clouds? Or would this require a whole cloud generation/simulation engine and be too much work?

[NickolausDS]

Visually no, this would only account for the force the thermal would apply on the flight physics engine. The effect would be the ability to fly in circles to gain hight without expending energy.

The way this will be implemented is still on the drawing board. Ideally, thermals would generate according to albedo and sun exposure, adhere to terrain as they formed, then mushroom and visually condense into clouds once they reached the altitude of dew point. In actuality, the first iteration will probably be implemented as simple invisible spheres in the world that accelerate flight objects against the force of gravity.

So in effect, no. Cloud generation will be up to you.