Yaw angle

You can use the cos of the dot product of the two vectors for this.

Make sure they are both have a length of 1 first, however, or you'll get funny results.

http://freespace.virgin.net/hugo.elias/routines/r_dot.htm
^ Explains the dot product if you are not familiar with it, and shows how to get the angle between the vectors from it.

Quote:

Original post by CombatWombat You can use the cos of the dot product of the two vectors for this. Make sure they are both have a length of 1 first, however, or you'll get funny results.

Do you mean "arc cosine"?


-Josh

Another method that is in some ways superior to the acos() method is to use atan2(). Presumably your character has a forward vector that reflects its current rotation. You can then find the signed angle to a target like this:

Vector3 diff = target-position;
dot = diff.x*forward.x+diff.z*forward.z;
perpdot = diff.z*forward.x-diff.x*forward.z;
yaw_delta = atan2(perpdot,dot);
// *Convert from radians to degrees if necessary*

You may have to swap and/or negate the arguments to atan2(), depending on which direction you consider to be forward when no rotation has been applied.

Thank you all for such fast response.
I had come across these methods when i was trying to find a solution. My actual problem is that i dont know how to get the forward vector. :(
sorry for not stating my exact problem.

Quote:

My actual problem is that i dont know how to get the forward vector. :(

Since this is essentially a 2d problem, the forward vector is simply constructed from sin(yaw) and cos(yaw). For example, if you want +z to be forward when yaw = 0, you might construct the forward vector like this:

// *convert to radians if necessary*

forward.set(sin(yaw), 0.0f, cos(yaw));

Thank you all for helping me out.
especially CombatWombat,Josh and jyk. This should solve me problem.

**proud to be part of such a helpfull community**