SRL Archive - Help and Support

Well I am trying to make a function that calculates the angle of a point from a point.

Like XX, YY, OriginX, OriginY.

What I have so far:

program New;
Var
  ASArray, ACArray: TExtendedArray;

Procedure LoadArcSinArray;
Var
  I: Integer;
Begin
  SetArrayLength(ASArray, 360);
  For I := 0 To 359 Do
  Begin
    ASArray[i] := ArcSin(Sin((I / 180) * Pi));
    Writeln('AS: '+IntToStr(i)+' : '+FloatToStr(ASArray[i]));
  End;
End;

Procedure LoadArcCosArray;
Var
  I: Integer;
Begin
  SetArrayLength(ACArray, 360);
  For I := 0 To 359 Do
  Begin
    ACArray[i] := ArcCos(Cos((I / 180) * Pi));
    Writeln('AC: '+IntToStr(i)+' : '+FloatToStr(ACArray[i]));
  End;
End;

Procedure InFloatArrayEx(E: Extended; EA: TExtendedArray; Var Where: Integer);
Var
  I: Integer;
Begin
  For I := 0 To High(EA) Do
  Begin
     If E = EA[i] Then
     Begin
       Where := I;
       Exit;
     End;
  End;
End;

Function AngleOf(xx, yy, ox, oy: Integer): Integer;
Var
  A, I, R: Integer;
Begin
  R := Distance(xx, yy, ox, oy);

End;

begin
  LoadArcCosArray;
  LoadArcSinArray;
end.

Its like XX = Ox + Radius * Cos(Radians(Angle - 90))

and I want to find out the angle, does somebody understand what I am trying to say?

Help appreciated a lot!

function LineAngle(Point1, Point2: TPoint): Extended;
var
  X, Y: Extended;
begin
  X := Point2.X - Point1.X;
  Y := Point2.Y - Point1.Y;
  Result := Degrees(ArcTan2(X, Y));
end;

O.o

Seriously?

EDIT: ArcTan2 is divine…

EDIT EDIT: Forgot to thank you, thanks !

Although the ArcTan returned in Kevin's example might not be the angle you're looking for. For example:

Function GetCompassAngle: Extended;

Var
   Compass: TPointArray;
   Point: TPoint;
   
Begin
  FindColorsTolerance(Compass, 1911089, 540, 2, 590, 40, 0);
  If Length(Compass) < 1 Then
    Exit;
  Point := MiddleTPA(Compass);
  Result := Degrees(ArcTan2(Point.Y - 20, Point.X - 561)) + 90;
  If (Result < 0) Then
    Result := Result + 360;
End;

Note the + 90;
And If Result < 0 Then
…

This returns the degrees like you would like them to appear when getting the compass angle.

But purely math, Kevin's right. It just depends what you will use it for.

But I use for things where I need 0-360 so +90/ +360 it is?

Shame there isn't any of these interesting stuff on my grade :(

function GetAngle(x1, y1, x2, y2: Integer): Extended;
begin
  Result:= (x2 - x1) / (y2 - y1);
end;

Not it?

But thats just the Tan or is it arc?

Dunno :p.

Thats just the slope. :)
You need to preform an arctan on the slope.

And Tan = Slope!

Yes, I was right! Yay!

EDIT: Wizzy can you make a Tut of useful trigs?

No… The Slope is

function Slope(x1, y1, x2, y2: extended): Extended;
begin
   Result:= (y2 - y1) / (x2 - x1);
end;

Remember Rise / Run Also Y / X

SKy.

Tan = Sin / Cos.

AKA

Slope = y / x

From: Wizzup?
SKy.

Tan = Sin / Cos.

AKA

Slope = y / x

Uhmm Thanks for reminding me…? :p

From: Wizzup?
SKy.

Tan = Sin / Cos.

AKA

Slope = y / x

Uhmm Thanks for reminding me…? :p

Sense i knew that XD, but thanks…