How to rotate a scene node towards a point?

Weng · Post by **Weng** » Tue Jan 20, 2009 4:16 pm

I would like to rotate a fairie node towards a point where the player right clicked.

According to some maths formula I've read, the approach seems to be like this:

1. Find the vector where the node is facing
2. Find the vector from the node's position to the position where the player clicked
3. Normalize both the above vectors
4. Take the dot product between these 2 and arc cosine the result to get the angle to rotate
5. Use setRotate on the y axis to rotate the node

The problem is, how do I find out the vector where the node is facing?

Also, is the above approach correct? I've read that rotation is best done using matrices, instead of setting the y axis to rotate by an angle.

JP · Post by JP » Tue Jan 20, 2009 4:43 pm

It's been discussed many times before, try searching for rotateToFace and you may well find a working function.

rogerborg · Post by **rogerborg** » Tue Jan 20, 2009 4:43 pm

If you just want to rotate around the Y axis, then it's fairly simple.

Calculate the vector from the moving node to the target position. Call vector.getHorizontalAngle() on it. That will get you 3 Euler rotations, of which only X and Y will be non 0. You can ignore the X rotation, and then simply change your moving node's Y rotation until it matches the target Y rotation, and then off you go.