Compass Math

[Freddy1990]

Well, I'm going to kick the compass and minimap angle functions out of SCAR soon because I feel that it's more convenient for the scripters to make them themselves so they can also be fast and easily updated. And I'm confident that they will do a great job for it, so I'm releasing the math algorithm for my compass function. (Not saying it's better than what people are currently using, but it might offer some insight...

dX1 := mx - tx;
dY1 := my - ty;
dX2 := mx - pp.x;
dY2 := my - pp.y;
tmp := ((dX1 * dX2) + (dY1 * dY2)) / (Sqrt(Sqr(dX1) + Sqr(dY1)) * Sqrt(Sqr(dX2) + Sqr(dY2)));
Result := Abs(ArcCos(tmp) - Pi);
if pp.x > mx then Result := 2 * Pi - Result;

mx and my are the coordinates of the center point of the compass.
tx and ty are the coordinates of the middle, top point of the compass. (The highest point on the compass, at the same x coordinate as the center)
pp is the point at which the South indicator is located.

As some might've noticed, my algorithm is based on the law of cosines.

(Note that this is for calculating the radians)
(You might also have noticed that "dX1 := mx - tx;" will always be 0, but I just made it that way in case I'd ever need to change it)

if you leave out dX1 you'd get:

dY1 := my - ty;
dX2 := mx - pp.x;
dY2 := my - pp.y;
tmp := (dY1 * dY2) / (dY1 * Sqrt(Sqr(dX2) + Sqr(dY2)));
Result := Abs(ArcCos(tmp) - Pi);
if pp.x > mx then Result := 2 * Pi - Result;

[Wizzup?]

Always been wondering how you did. Nice, using cosine laws.

[TheSantaMan]

lol, don't even know what that means. Just guess i'm not smart enough

[mickaliscious]

lol, don't even know what that means. Just guess i'm not smart enough

I understand it, but hopefully SRL will just take over for all the rs_GetCompassAngle and other functions using this math... It will save me a few headaches.


...So we would have to input pp since that changes? Thats the only problem I'm having with trying to fix the MakeCompass() error due to the rs_GetCompassAngle begin 'broken'.

[mastaraymond]

Advanced.

[mickaliscious]

...I figured out a way for it to work but its not 100% accurate. Use a dtm of the N and reflect its coords across the centerpoint to find the South indicator location.

[Freddy1990]

...I figured out a way for it to work but its not 100% accurate. Use a dtm of the N and reflect its coords across the centerpoint to find the South indicator location.

I did a similar thing when I first developed the function, but it caused it to mess up in certain situation, it used findcolor rather than a dtm though. In the manual I thank ruler and geno for parts of the compass function, that's actually the part to get that point, it's uses a piece of code converted from ibot, since ibot seemed to use skipboxes which I had written myself once and later implemented in SCAR, so it was easy to modify to use my own skipboxfunctions. But there's many ways to do it really...

[WT-Fakawi]

Good of you to skip this from SCAR, and thanks for sharing. You are right, it should not be there in the first place. SCAR is so much more versatile...

[R0b0t1]

...


My head almost blew up. Back to wikipedia.

[Kasi]

wow this is the fist time iv seen freddy post

[NiCbaZ]

that post was a pure spam post that post had nothing to do with the topic,


Freddy THis is very interesting, will it be in the next scar.?

[WT-Fakawi]

that post was a pure spam post that post had nothing to do with the topic,


Freddy THis is very interesting, will it be in the next scar.?

"Quote of the Day"

[Town]

"Quote of the Day"

Epic.

[R0b0t1]

Fakawi: Epic Win.

Nicbaz: Epic Fail.

R0b0t1: Head blown up by super maths, he now goes to wikipedia to make sense of the situation.

[mickaliscious]

Fakawi: Epic Win.

Nicbaz: Epic Fail.

R0b0t1: Head blown up by super maths, he now goes to wikipedia to make sense of the situation.

Its just trigonometry dude. Theres no super maths there.

[gamer 5]

It will take a while to get used to

MakeCompass(" ") is like so easy!

[R0b0t1]

if (Trigonometry.Length >= 10) { cout "Dubya Tee Eff Mate?"; };

[Markus]

"Quote of the Day"

Amen

[/offtopic]

So, can I use it like this? Get north indicator, use skipboxes for west and east, then find south and calculate.

[TheGuyWhoGotOn]

Well I'm trying this now I feel like I'm doing something wrong...

function GetCompassDegrees: extended;
var dx1, dx2, dy1, dy2: integer;
    tmp: extended;
    pp: TPoint;
begin
  pp.x := 557;
  pp.y := 24;
  dX1 := 543 - 543;
  dY1 := 24 - 8;
  dX2 := 543 - pp.x;
  dY2 := 24 - pp.y;
  tmp := ((dX1 * dX2) + (dY1 * dY2)) / (Sqrt(Sqr(dX1) + Sqr(dY1)) * Sqrt(Sqr(dX2) + Sqr(dY2)));
  Result := Abs(ArcCos(tmp) - Pi);
  if pp.x > 544 then Result := 2 * Pi - Result;
end;

Now that results in 4.71238898038469 so is there something I have to do after? I was thinking it would be more around 270 degrees.

What am I doing wrong?

Edit: Ok after I tried this:

function GetCompassRadians: extended;
var dx2, dy1, dy2: integer;
    tmp: extended;
    pp: TPoint;
begin
  pp.x := 557;
  pp.y := 24;
  dY1 := 24 - 8;
  dX2 := 543 - pp.x;
  dY2 := 24 - pp.y;
  tmp := (dY1 * dY2) / (dY1 * Sqrt(Sqr(dX2) + Sqr(dY2)));
  Result := Abs(ArcCos(tmp) - Pi);
  if pp.x > 543 then Result := 2 * Pi - Result;
end;

However guess what? I got 4.71238898038469...

[Wizzup?]

Doh. You use nothing but constants.

[Freddy1990]

TGWGO, you need to convert it to degrees

function GetCompassDegrees: Extended;
begin
  Result := Degrees(GetCompassRadians);
end;

It was originally designed to work with degrees, but I changed it to radians

Its just trigonometry dude. Theres no super maths there.

I have to agree with that

[TheGuyWhoGotOn]

TGWGO, you need to convert it to degrees

function GetCompassDegrees: Extended;
begin
  Result := Degrees(GetCompassRadians);
end;

It was originally designed to work with degrees, but I changed it to radians



I have to agree with that

Thanks so I'm doing nothing wrong? Awesome...

@Wizzup?: I think only the TPoints need to be changed so I didn't make them constants.

FTW works now...Now to make it find the south indicator...Not 100% sure of how to go about this...

[SKy Scripter]

I just did

{-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
  function GetCompassAngleDegrees: extended;
  By: SKy Scripter
  Description: Gets The Mini Map Degrees Ranging From 0 - 360
  Note: I Do Know That In ArcTan2, I Have The X Where The Y Should be.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-}
function GetCompassAngleDegrees: extended;
var
   mx, my: Integer;
   P: TPointArray;
begin
   FindColorsTolerance(P, 1911089, 520, 5, 560, 45, 0);
   TPAAverage(P, mx, my);
   if (Mx <> 0) then
    Result := FixD( -Degrees(ArcTan2(543 - mx, 24 - my)) );
end;

[Toterache]

Urgh, my head is spinning, but i think a few more hours and I'll be able to understand this thing ( trigonometry is something that would have been taught next year, but i switched back from the USA to Germany, and here all we are learning are quadratic equations {not sure how to spell it in english}, so trigonometry is still an unkown area for me {I'm only a 9th grader atm}). But still, thanks a lot, will be a nice challenge.

[Freddy1990]

I just did

{-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
  function GetCompassAngleDegrees: extended;
  By: SKy Scripter
  Description: Gets The Mini Map Degrees Ranging From 0 - 360
  Note: I Do Know That In ArcTan2, I Have The X Where The Y Should be.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-}
function GetCompassAngleDegrees: extended;
var
   mx, my: Integer;
   P: TPointArray;
begin
   FindColorsTolerance(P, 1911089, 520, 5, 560, 45, 0);
   TPAAverage(P, mx, my);
   if (Mx <> 0) then
    Result := FixD( -Degrees(ArcTan2(543 - mx, 24 - my)) );
end;

that's another way to do it