Question

This is what I have

• I have a plane in 2D X,Y
• I set his destination by clicking on the screen X’, Y’
• I calculate the angle it needs to turn to face this destination with:

// Calculate the angle between plane position and destination point

CVector3 facingVec = m_vDestination - m_vPosition;
fAngle = -Math::radiansToDegrees (  (float)atan2f(m_vDestination.x - m_vPosition.x, m_vDestination.y - m_vPosition.y)  )  ;

//This doesn't work, when rotating from ex. 350 degree to 0 
//plane has to go all the way around 360,350,340,330,
//...,120,...100,90,..down to zero
float angleToTurn = fAngle - m_fRotationAngle;
if(angleToTurn < 0)
{
    angleToTurn += 360.0f;
}

m_fRotationAngle += (angleToTurn) / 5;

// Move the unit towards the calculated angle m_fRotationAngle

m_vDirection.x =   (-sin(Math::degreesToRadians(m_fRotationAngle)));
m_vDirection.y =   (cos(Math::degreesToRadians(m_fRotationAngle)));

m_vPosition += ( 2 * m_vDirection * fDelta);

This is how it looks like

YT Video – sorry for the demo version, i couldn’t get anything free at this moment.

This is what I need

• I need this to behave properly, let’s say plane is rotated at angle 350.
  I set the destination and new angle should be 15.

Instead of going: 350,340,330,320,310,300,290,…10,0,15
It should continue: 350,0,15

Hope you can help me out with this guys, I’ve already dropped bezier approach – and I’m struggling with this since few days now.

Answer 1

If I read this correctly, you’re trying to find the smallest angle to interpolate between the two vectors? If so, the following algorithm should work:

1. Find the angle of the first vector, relative to the fixed vector [1, 0]. This is a1.
2. Find the angle of the second vector, relative to the fixed vector [1, 0]. This is a2.
3. Let da = a2 – a1.
4. if da > 180, da -= 360;
5. else if da < 180, da += 360;

You need to calculate the angles with respect to another third vector [1, 0] so you can determine weather to rotate left or right.

Edit: I saw your YouTube link was broken, now I see it’s working again. I think my answer is what you’re after.