Weapons for FSX
Contrary to my intentions I have not posted much lately. I've started my new work and it takes a lot of my time, but primarily much of my mental focus. However I have been able to do some stuff that so far is more like a prototype than anything actually working. I've been working on adding weapons to FSX.
The main idea is to add weapon objects into the simulated world through a SimConnect client, simulate their behaviour (i.e. guidance) and then calculate and project the damage they inflict on other simulated objects. Simple enough. But it's much harder to implement than you might think first.
Due to the fact that the SimConnect communication is asynchronous, I cannot guarantee that the positions for my weapon objects correspond 100% to the other objects in the simulated world. This not a big problem when the weapons are fired since they are then free objects that aren't really affected by any other objects. However, before the weapons are fired, they are firmly connected to the aircraft's hardpoints and to avoid them jerking around, another solution had to be found. My idea is to make all possible ordinance for the aircraft a part of the 3D model. Then my SimConnect client tells the model what weapons should be visible at what hardpoint. When a weapon is released, my program simply tells the model to hide that weapon and replaces it with a new free object at that position. The drawback is that you have to edit the 3D model of the aircraft to allow it carry new weapon types. But compared to the alternative, I think it's acceptable.
The big problem is to position the new object. I'm not getting very good precision. It differs up to a meter or two. To position the new object (the weapon) I calculate a vector to the hardpoint from the center of the aircraft. Then I split this 3D vector into a 2D vector and a difference in latitude. The 2D vector is then used to calculate a latitude and longitude based on the aircraft's latitude and longitude. First I used a totally spherical earth model, since it's easiest and fastest, and I didn't think it would matter that much. But when I didn't get the precision I wanted I switched to WGS84 which is supposedly what FSX use. WGS84 did however not give me that much better precision, if any. I can't figure out where the problem is. Is it my formulas, is it in the communication with FSX or is it possibly a problem within FSX? I don't know if I will spend much more time on this or if I will just I accept the lack of precision. As it is now it's at least better than nothing.
Other things I have worked on is a crude targeting system similar to what you would find in early types of the Sidewinder missile - just point at the target and get a value of how good lock you have. Better targeting and communication, with for instance a targeting radar program, will be introduced later. I've also been able to make the released weapons fly where I want them to, and even make targeted aircrafts loose control and go down into the ground. Engine fire seems to be an exclusive feature for the player aircraft so I will have to add my own smoke and fire, and also make explosions when a missile hits a target. Further down the line I also plan to add multiplayer weapons and AI aircrafts that fights back, perhaps even SAMs and AAA shooting from the ground. But first I need to get the most simple stuff working.
