The actual model is a handful of cylinders and boxes; but for now I’m not too interested in how it looks. The interesting bit today was the bit that works out aim the gun so that the bullets travelling at speed b will collide with the plane travelling with velocity v at some time in the future t. My Maths is rather tragically rusty and it took me a considerable time to work out.

As it turns out you have end up having the bullet as a sphere of radius st on one side of the equation and the plane as a line parameterised by t on the other. If you rearrange the equation you can form it into a classic quadratic that you can then solve with the old x = (-b +/- sqrt(b^2 – 4ac)) / 2a formula. This normally gives you two possible times at which the bullet and the plane should collide, although one of them may be negative (in the past), in which case the only person you’ll hit is Dr. Who.

Once you have the time the bullet and the plane will collide you can work out where the plane will be at that time and aim there.

This currently only works for planes travelling in a straight line, but for now it’ll do.

That is all.

In then end it turned out I had another camera script running on the camera simultaneously which I’d forgotten about. Such a silly mistake cost me about two hours. Anyway, during this time I set the plane up to leave a trail behind it so that I could examine its motion – it’s pink because I haven’t assigned a texture to it. Anyway, it’s kind of fun so I left it in for the time being.

The main thing I’d wanted to do was to add some extra camera modes for looking around the player, and I’ve now done that as well. At the moment it snaps between camera positions, but I’ll smooth out the transition soon.

Click here to play.

Controls:

So what I’ve started on now is the AI. I knew I wanted to use something like a hierarchical finite state machine, and decided in the end to use behaviour trees, similar to those used in Halo 2. At first I used an existing implementation written for Unity called ‘Behave’, but I don’t like the way you always have to compile the tree before you use it. In the end I decided I’d prefer to write my own simpler system. It may not have the snazzy graphical editor, but it seems to work.

So far I’ve only got basic Take-off and follow AI. More soon, hopefully.

As an aside, I think I need to separate some of the aspects of my flight model apart, so guess I may be doing some refactoring soon.

No playable version today, I’m afraid.

Therefore, I’ve been reading around about the currently accepted wisdom for implementing networking, and it seems that Tim Sweeney’s Unreal Networking Architecture is the model most people seem to be basing their code on. I found a quite good summary of it here.

I have mixed feelings about this. It’s something I’d really like for the game, but I’d like to get more gameplay  code done first. However, if I don’t want to submit myself to a lot of pain later on I really need to get it sorted out now.

I’m just not really looking forward to it.

Actually, the taking off is kind of interesting. When flying I don’t use any of the built-in PhysX physical simulation that Unity provides, instead controlling all movement etc myself. This allows me to concentrate on the fun and feel of the flying without having to worry about the realism. However, one of the really useful things PhysX provides is collision detection – something that’s not so important in flight, but very important on the ground. Therefore when the plane is on the ground, its movement is controlled by applying various forces to it and allowing the simulation to run. Once the plane has taken off, I stop using the simulation completely, except to register damage to the plane if it hits the terrain.

Anyway, here’s the latest version:

Mouse controls movement

< and > (, and .) control throttle.

Click here to play

Recent improvements:
* Takeoff / landing
* On-ground behaviour
* Health
* Collision damage
* Explosion and fire one you’re out of health!

I’m not quite ready to put a new version up, but there will be one soon.

I didn’t have a lot of time to do much on this today, but it’s always nice to be able to tick something off the list :D .

For each plane type I can customise the amount of speed you can lose or gain depending on the angle that the plane is flying at. I’ve also got settings to adjust the maximum acceleration and deacceleration of the plane. All of this means that the plane will slowly slow down as you climb and you can get a real turn of speed as you dive. On the Sopwith I’ve set it so that you can accelerate faster than you can deaccelerate, which means that if you take a nice dive you can get up a nice bit of speed and keep going for a fair bit.

It’s not particularly realistic, but it seems to have quite a good feel to it.

I then decided I needed to add some stalling behaviour. It was a bit difficult to know the best way to do this; I don’t have any physics model that it would naturally fall out of so I had to think a bit about how I wanted it to behave. Stalling should:

• Cause the plane to lose altitude
• Cause the plane to spin around a bit
• Be a bit scary for the player
• Be recoverable from, after a little bit

So I started off by setting up a speed at which stalls kick in, and making the plane start to drop when you hit it, but the transition was very abrupt and didn’t give the player any warning – so I moved it to a system when the transition is gradual. To give the player a bit of warning, the plane now judders as it approaches a stall.

So I had it falling once the speed dropped between a certain level, with a fair warning to the player, but there was no way to escape from it, and it looked odd as it kept the same attitude as it fell. Therefore I made the plane gradually rotate down to face the ground; as it faces downwards it will speed up and eventually get beyond its stall speed and be able to fly properly again. I found that recovering from the stall was happening too quickly so I reduce the level of throttle just when in a stall, just to make it a bit harder to recover from.

Buahahaha.

Anyway, that’s still not enough – the plane just falls down a bit until it gets up enough speed to recover. Therefore I decided to make it spin, and I think that fulfils my requirements for a stall quite admirably.

After that I just had to spend a little time smoothing the transition between the pre-stall and stall modes, to make it look a little less ‘robotic’.

Try it out, and see what you think.

Instructions :
Movement – mouse
throttle , & .

Click here to play