Im currently coding a shoot em up, and I was wondering what the best way to implement pattern based AI is? My current idea is to create an array of accelerations that would be applied every few updates to the sprite... ie

int Acceleratons[50];

if(++iTimer > 5)
{
pSprite->vel.x += Accelerations.x;
pSprite->vel.x += Accelerations.y;
iTimer = 0;
i++;
}

Something like that, of course there would be checks to make sure the array wasn't finished and whatnot but that was the gist of the implementation that I thought up for pattern based AI ala Galaga style. Anything better? Or is that how it's done in those type of games too?

so something like this then?

int Accelerations[50];
float iTimer = 0;

if(iTimer > 5)
{
pSprite->vel.x += Accelerations.x;
pSprite->vel.x += Accelerations.y;
iTimer -= 5;
i++;
}

iTimer += GetTickCount();


As far as using a spline editor to define my paths, Ill have to look into that.

Would seem much easier for me at least to make the patterns! Although even with the array it would be populated with data from a separate program.

Yah for higher resolution under windows there is QueryPerformanceCounter() which gives you a pointer to the hardware clock.

I gotta figure out what there is for SDL but that shouldn't be a problem.

Thanks!

I know half the fun is doing it yourself... but more hours of sleep is also fun... so, anyone has a spline editor source code?

Well, i don't think you need a full-blown spline editor for rock n roll. What you might look for is a regular "spline thingy" on the internet (i'm thinking someone out there must have a java applet for that sort of thing). Then just take the "points" when you make a line you like and hardcode those into your game.

I think you would find it very usefull to program an "interpolator" class that works like this:

Interpolator i;
i.DefineCurve(CURVE_SPLINE);
i.DefinePoints( /* a list of points*/ );

Then when you need a value on the graph, you just ask:
i.GetValue( time );

Basically you are defining a little graph. You set limits on the graph for time (say, from 0-5 seconds) and then define the points for the values. That way you can rip out any position from any point in time:

Interpolator x;
Interpolator y;
/* set up points here */

// move a unit's x/y position:
Unit.MoveTo( x.GetValue(time), y.GetValue(time) )


I have something like this already, but it's only linear. No fancy curve fitting. I think you would find this sort of thing handy though, so if you program it now you can keep it forever. You might also look around and see if anyone else already made something like it. I'm sure someone has.