Talk:Wall Smoothing/Implementations/NonIterative

From old wiki
For what it's worth, my published WallSmoothing method does use iteration, but will only loop a maximum of two times in any situation, I think. I just put the 25loop limit on the iteration as a form of personal infiniteloop paranoia. I'll take a closer look at yours when the alcohol wears off... ;)  Voidious
I added a line to the end of your method which prints out the value of g right before the function returns. It was always 26. Perhaps I'm not passing your method the right parameters? I can send you the code to check if you like. David Alves
Yikes! I will look into this. I might be just ganking your method soon if that's the case...  Voidious
Ok  as implemented in Dookious, I just ran a couple matches and the value of g is never greater than 2. Maybe something got lost in translation when I posted it on the wiki; I'll take a look later when I get a chance. Thanks for the heads up on that. If you want me to check the code, feel free to email to me, my emails on the ContactInfo page.  Voidious
Here's a version that's a bit cleaner to look at, if anyone is interested. It is geared for driving at a given heading, not toward a given point.
HALF_PI = Math.PI / 2;
WALKING_STICK = 120;
WALL_MARGIN = 18;
S = WALL_MARGIN;
W = WALL_MARGIN;
N = 600  WALL_MARGIN;
E = 800  WALL_MARGIN;
// angle = the angle you'd like to go if there weren't any walls
// oDir = 1 if you are currently orbiting the enemy clockwise
// 1 if you are currently orbiting the enemy counterclockwise
// returns the angle you should travel to avoid walls
double smooth(double angle, int oDir) {
angle = smoothWest(N  getY(), angle  HALF_PI, oDir) + HALF_PI;
angle = smoothWest(E  getX(), angle + Math.PI, oDir)  Math.PI;
angle = smoothWest(getY()  S, angle + HALF_PI, oDir)  HALF_PI;
angle = smoothWest(getX()  W, angle, oDir);
// for bots that could calculate an angle that is pointing pretty far
// into a corner, these three lines may be necessary when travelling
// counterclockwise (since the smoothing above may have moved the
// walking stick into another wall)
angle = smoothWest(getY()  S, angle + HALF_PI, oDir)  HALF_PI;
angle = smoothWest(E  getX(), angle + Math.PI, oDir)  Math.PI;
angle = smoothWest(N  getY(), angle  HALF_PI, oDir) + HALF_PI;
return angle;
}
// smooths agains the west wall
double smoothWest(double dist, double angle, int oDir) {
if (dist < WALKING_STICK * Math.sin(angle)) {
return Math.acos(oDir * dist / WALKING_STICK)  oDir * HALF_PI;
}
return angle;
}
 Simonton
Well done, much cleaner then my prototype version I have bee working on, and with half the code. I guess I have a ways to go, think you can build a better wall distance function too? Chasesan
Small notes there Simonton, it doesn't seem to work counter clockwise, and it kinda sticks in the upper left corner on approach. Chasesan
Oops! I should know better than to adapt my code to something more standard without testing it first. There, try that :). Oh ... and what's a "wall distance function"? Oh wait ... the distance forward to a wall? Um, hold on a minute ...  Simonton
Not sure, but Chasesan might be referring to the "orbital" wall distance style that a lot of bots use: assuming the enemy tank continues in a standard orbit, at what GF would it be when it hits a wall? CassiusClay and Dookious do it with brute force, checking every .01 GFs until they find a projected enemy location off the map.  Voidious
Works great, minor problems in Genesis, but those are my fault. This method will soon probably replace all the other methods just cause its so much faster then the smallest but still small itself.
Another note, the method seems to act oddly at some stick sizes, have you tested more then 120? Chasesan
No, that sounds strange. How much larger?  Simonton
Actually no, I ran a test, it just seems i'm used to other kinds of smoothing. Its just working too well, making me think its not working correctly. Chasesan
I just tested this code, it works better than almost all other wall smoothing functions I have tried, except for the persistent sticking bug Chasesan noted. I have seen the bot get stuck when going counterclockwise in the upperleft corner, and possibly when going clockwise in the lowerright corner. Do you have any idea what is causing this? AaronR
Hmm. I use a variation of this in WeeksOnEnd, so I can't run it right now to see (not enough time to create a bot to use it). I thought I tested it before ... maybe I can be of more help later, but probably not right away.  Simonton
Thanks anyway. If you do go hunting for the bug, here is what I have figured out:
 It always occurs when going counterclockwise.
 The bot can get stuck in any corner, but most frequently in the upperleft corner.
 When it does get stuck, the bot can sometimes escape by reversing direction, this is why the bug is not visible in a typical bot.
The easiest way I have found to reproduce this bug is to create a bot that always moves counterclockwise and keep running rounds until it starts a round very close to or inside the smoothing radius in the upperleft corner, at which point it will just vibrate back and forth. If you then make the bot reverse direction, it may shoot off on a diagonal instead of moving clockwise normally  a response very similar to what happens in other wallsmoothing algorithms if you try to head in one direction with the angle and the other with the orientation.
 AaronR
You could just program the bot, so that when your bot is within radius r (the smoothing radius) of the wall to move outside it, then allow the smoother to work as normal (though, this could lead to a pattern matcher catching on, though it is a rather small window). Since I assume this happens near the corners, move along the wall a little ways, not out into the field (it can look rather innocent if you move that way, even to a patternmatcher).
An easier way, though I doupt that there is an easy way to fix the bug in the method, without something of that sort anyway. Perhaps a check, and if within, use the radius to the wall your heading towards (maybe 8 less, to make up for velocity), make sure only to check if say, 5 or more within the radius, to allow room for error.
Oh, wow, sorry, I totally forgot about this. I also never saw you latest post, AaronR. Um, I may be able to check this out tonight. By the way, if you look at the opening .battle file you'll see a way to specify the starting position of a bot, which sounds like an easier way to reproduce the bug :).  Simonton
Alrighty. I was unable to replicate the getting stuck behavior, but I did find a bug. I should like you to add the three new lines above & let me know if it fixes your problem.  Simonton
Well, it seems this "bug" was my fault all along. The code I was using looked like this:
public void onScannedRobot(ScannedRobotEvent e) {
double angle = smooth(getHeadingRadians(), 1);
setBackAsFront(angle);
}
So one quarter or so of the time the bot was doing exactly what I said before: "trying to head in one direction with the angle and the other with the orientation". As long as you feed the method legal input, it seems to work correctly. However, I found another bug: the stick size is too small, and some bots will frequently hit the second or third wall they encounter. Changing the stick size to the other common value of 160 removes this problem.
 AaronR
Ah. That would do it. And you're right, that stick size is a bit small. 123 is the minimum to guarantee missing the wall, IF you never approach the wall at greater than a 90 degree angle (actually 122.something). If you are retreating from the enemy at the same time as approaching the wall, there will be times that you need a longer stick. Also, again, those three new lines above may be necessary depending on the way you calculate your desired angle, as mentioned in the new comments. Happy smoothing!  Simonton
Angle Based version of face code
//no object creation or method calling if we can help it, need this to stay fast and rather memory unintensive
//px = position x
//py = position y
//angle = angle we are trying to travel
//direction = orbit direction (> 0 = clockwise, anything else is counterclockwise)
//fw = field width
//fh = field height
//c2pd = orbit center to position distance
public static final double fastSmooth(double px, double py, double angle, int direction,
double fw, double fh, double c2pd) {
final double margin = 18;
double stick = 150;
if(c2pd < stick) stick = c2pd;
double stickSq = stick*stick;
double nx = px + stick*Math.sin(angle);
double ny = py + stick*Math.cos(angle);
if(nx >= margin && nx <= fw  margin && ny >= margin && ny <= fh  margin)
return angle;
/* TOP */
if(ny > fh  margin  py > fh  stick  margin) {
//System.out.println("top");
/* RIGHT */
if(nx > fw  margin  px > fw  stick  margin) {
//System.out.println("right");
if(direction > 0) {
//smooth right
stick = fw  margin  px;
nx = fw  margin;
ny = py  direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
} else {
//smooth top
stick = fh  margin  py;
nx = px + direction * Math.sqrt(stickSq  stick*stick);
ny = fh  margin;
return Math.atan2(nxpx, nypy);
}
} else /* LEFT */ if(nx < margin  px < stick + margin) {
//System.out.println("left");
if(direction > 0) {
//smooth top
stick = fh  margin  py;
nx = px + direction * Math.sqrt(stickSq  stick*stick);
ny = fh  margin;
return Math.atan2(nxpx, nypy);
} else {
//smooth left
stick = px  margin;
nx = margin;
ny = py + direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
}
}
//smooth top
stick = fh  margin  py;
nx = px + direction * Math.sqrt(stickSq  stick*stick);
ny = fh  margin;
return Math.atan2(nxpx, nypy);
} else /* BOTTOM */ if(ny < margin  py < stick + margin) {
/* RIGHT */
if(nx > fw  margin  px > fw  stick  margin) {
if(direction > 0) {
//smooth bottom
stick = py  margin;
nx = px  direction * Math.sqrt(stickSq  stick*stick);
ny = margin;
return Math.atan2(nxpx, nypy);
} else {
//smooth right
stick = fw  margin  px;
nx = fw  margin;
ny = py  direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
}
} else /* LEFT */ if(nx < margin  px < stick + margin) {
if(direction > 0) {
//smooth left
stick = px  margin;
nx = margin;
ny = py + direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
} else {
//smooth bottom
stick = py  margin;
nx = px  direction * Math.sqrt(stickSq  stick*stick);
ny = margin;
return Math.atan2(nxpx, nypy);
}
}
//smooth bottom
stick = py  margin;
nx = px  direction * Math.sqrt(stickSq  stick*stick);
ny = margin;
return Math.atan2(nxpx, nypy);
}
/* RIGHT */
if(nx > fw  margin  px > fw  stick  margin) {
stick = fw  margin  px;
nx = fwmargin;
ny = py  direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
} else /* LEFT */ if(nx < margin  px < stick + margin) {
stick = px  margin;
nx = margin;
ny = py+direction * Math.sqrt(stickSq  stick*stick);
return Math.atan2(nxpx, nypy);
}
System.err.println("Something is really messed up here... (check your wall smoothing code!)");
return angle;
}