How can I calculate the rotation value of a model to look at a position?

Troubleshooting General Help
19

If you can only turn left or right to get there… then the target is either “turn to the left” or “turn to the right”.

How would you calculate that with a y angle?

With a couple of dot products it’s simple.

Given: Spatial target, Spatial player… we want to figure out if player should turn left or right:

// Find the direction we want
Vector3f relativeDir = target.getWorldTranslation().subtract(player.getWorldTranslation()).normalizeLocal();

// Find the direction we're looking and the left vector
Vector3f fwdDir = player.getWorldTranslation().mult(Vector3f.UNIT_Z);
Vector3f leftDir = player.getWorldTranslation().mult(Vector3f.UNIT_X):

// Is it in front of us or behind us and how much?
float front = fwd.dot(relativeDir);

// Is it to the left or right and how much?
float left = leftDir.dot(relativeDir);
// left < 0, target is to the right, left > 0 target is to the left

// If it's behind us then just max out left or right
if( front < 0 ) {
    left = FastMath.sign(left);
    // Except if it's _exactly_ behind us the just pick left or right
    if( left == 0 ) {
        left = 1;
    }
}

// Now turn left/right scaled by the left value -1 = max right turn, 1 = max left turn... 0.5 = half speed left turn, etc.
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