Hi all, hope you had a good weekend :). I should be able to do this but for some reason not wrapping my mind around it. The following code rotates a given point around an origin, usually the center. Proven, straightforward math.
Works as it should but with one caveat for certain applications - the desired rotation angle is always added to the previous angle, so that each time this is called and a new angle(0-360 degrees) passed, it will keep adding the angles together and go nuts if you want to, say, use it for rotation with a slider control.
Is it possible to modify this so as to always reference rotation from zero? Then one could simply set the desired angle of rotation to a number from 0 to 360, every time.
I've been experimenting for the last few days but not getting my desired result :(. I'm fairly proficient with basic trig functions but this one has me baffled! :). any help much appreciated.
Code:
Private Function RotatePoint(ByRef pointToRotate As POINTF, ByVal angle As Single, ByRef Origin As POINTF) As POINTF
Const pi As Single = 3.141593
Dim RadAngle As Double
Dim X As Double
Dim Y As Double
Dim StartAngle As Double
Dim EndAngle As Double
Dim Radius As Double
Dim NewX As Single
Dim NewY As Single
'- Convert degrees to Radians
RadAngle = 2 * pi * angle / 360
'- Find angle between origin and point to rotate
X = pointToRotate.X - (Origin.X)
Y = pointToRotate.Y - (Origin.Y)
If X = 0 Then X = 0.00001
StartAngle = Atn(Y / X)
'- Add the desired angle with which to rotate
EndAngle = StartAngle + RadAngle
'- Calculate Radius
Radius = X / Cos(StartAngle)
'- Find location of point after rotation
NewX = CSng(Radius * Cos(EndAngle))
NewY = CSng(Radius * Sin(EndAngle))
'- Return new point position
RotatePoint.X = NewX + Origin.X
RotatePoint.Y = NewY + Origin.Y
End FunctionWorks as it should but with one caveat for certain applications - the desired rotation angle is always added to the previous angle, so that each time this is called and a new angle(0-360 degrees) passed, it will keep adding the angles together and go nuts if you want to, say, use it for rotation with a slider control.
Is it possible to modify this so as to always reference rotation from zero? Then one could simply set the desired angle of rotation to a number from 0 to 360, every time.
I've been experimenting for the last few days but not getting my desired result :(. I'm fairly proficient with basic trig functions but this one has me baffled! :). any help much appreciated.