I'm new to robocode, and the learning curve is quite steep.
To phrase that another way, at one point my robot was locking on quite nicely to other robots, but subsequent versions (and prior versions) never appear to do anything sensible.
I'm an experienced programmer with lots of C and a bit of Java under my belt, so it's not the programming I'm struggling with.
I can get help with the specific physics questions (how do you get the angle between two headings? for example), so it's not that either.
I really just need someone who I can fire off a question "what does this do?" or "how does this work?" and get a simple response or a link to a wiki page.
I think if some sort of "big brother" mentorship programme were set up, a lot of people who would otherwise be put off by the massive learning curve might be encouraged to join in. More robots = more challenge = more fun. Right? :)
Until such a programme is set up, is there anybody out there who'd like to take a newbie under their wing? Please? :)
I would say just make yourself at home on the wiki and post all the questions you like. You'll probably get better / faster responses giving everyone a chance to answer them. Most of us watch Recent Changes and are happy to help. =) I'd also love to hear what kind of intro / tutorial pages would have been helpful to you, once you get your footing.
Welcome to the RoboWiki!
Ok, I guess the format of the Wiki and the highly-conversational style are throwing me a bit. I wasn't expecting a response so quickly (or at all, for that matter).
I think a brief primer on the physics/maths calculations you'll need for robocode would be useful, eg:
- how to calculate the difference between two headings - how to calculate the relative velocity of another bot vs your bot (don't know if this is used in any of the 'top' algorithms, but it feels like it could be useful to newbie bot authors) - how/why to normalise headings to relative angles (I know the Utils class has this, but it would be useful for newbie bot developers to know how to do it themselves and why it's useful) - how to calculate the distance between two headings (subtle difference between this and the first point)
If this already exists, could someone point me in the right direction?
I'm not sure if this is covered explicitly anywhere - I know for all of the geometry problems I run into I sketch it on paper then solve it traditionally.
That said, the difference between two headings is just (scan1 - scan2). You might want to use normalisation - either relative or absolute - to put it in the range you want.
On this wiki we generally refer to relative velocity in terms of its components - Lateral_Velocity and Advancing_Velocity. The pages for those explain how to calculate them, and yes, they are used in a lot of the more advanced algorithms =)
Relative normalisation is used for determining how far something is to the left or right - for instance, whether you should turn your gun left or right. It puts the angle between -Pi and +Pi (or -180 and +180). Absolute normalisation is usually used to figure out where something is 'relative to North' and gives a value between 0 and 2*Pi (or 0 and 360).
As to your last question, I'm not sure exactly what you're asking. Perhaps you want the absolute value of the heading difference? If so, take the relative normal angle first so you don't get the situation where one is on 355 degrees and the other 5 degrees, and the difference between them is 350 degrees instead of 10.
scan1-scan2 is over-simplified, if you want the -shortest- difference between the two headings, which is more useful, it should be: `360 - Math.max(scan1,scan2) + Math.min(scan1,scan2)` I think. Different when dealing in radians (obviously).
The last question is a little difficult to phrase, but no I'm not talking about the absolute value of the heading difference. I'm talking about calculating the distance between two points on two given headings. Using trigonometry. Eg "where is the bullet the robot I just scanned just fired? if he fired one", I know this specific example is impossible to model exactly, but for modelling best-guesses of enemies' guns I would imagine this kind of equation would come in handy.
Thanks for the links to Lateral and Advancing Velocities, it makes sense that they're used a lot in the more advanced algorithms, but those algorithms are all pretty much magic to me at the moment so I had absolutely no idea what is and isn't used.
I'm also not asking for specific answers to these questions, just asking if it might be wise to set up a wiki page that has some basic physics for the purposes of other newbies who don't have answers to the questions (I do, because my dad teaches A-level physics). But thanks for your answers nonetheless, as they did help clarify one or two points I wasn't sure about. :)
I'd take the difference, then normalise it relatively and take the absolute value.
As for the other one, you probably want to look at projecting a point from an origin location, a certain distance at a certain angle. If you look in the source of Raiko (or pretty much any other open source bot) you'll see the 'project' function. Once you have the new location of the point, you can calculate the distance the normal way, sqrt((x1-x2)^2 + (y1 - y2)^2).