I have a weapon mesh, how do I make it rotate GRADUALLY to look at the player (target)?
I want to update pitch, yaw, roll gradually and find out when the rotation is done.
I have a weapon mesh, how do I make it rotate GRADUALLY to look at the player (target)?
I want to update pitch, yaw, roll gradually and find out when the rotation is done.
It might be easier to use D3DXQUATERNION. Calculate a quaternion reflecting the current mesh orientation [ you could use D3DXQuaternionRotationYawPitchRoll(...) to start with ], named, for instance, startQuat. Calculate a second quaternion for the desired orientation (pointing at the target) named, for instance, finalQuat.
Use a quaternion named, for instance, meshQuat, for orienting the weapon mesh.
Then use D3DXQuaternionSlerp( &meshQuat, &startQuat, &finalQuat, delta ), where delta is incremented at your desired "gradual" rate from 0 to 1, perhaps a function of elapsed time or incremented by a delta-time from your render loop. When delta==1.0f, the rotation is done.
EDIT: For the weapon mesh orientation each frame, you can convert with D3DXMatrixRotationQuaternion(&meshMatrix, &meshQuat);
@Buckeye: If I have the target point that the weapon mesh should look at, how do I calculate finalQuat?
First, your primary inputs are the gun position and the target position.how do I make it rotate GRADUALLY to look at the player (target)?
vForward = vTargetPos - vGunPos;
vRight = Vector( 0, 1, 0 ) % vForward; // % = cross product.
vUp = vForward % vRight;
vRight.Normalize(); // Matrix row 0.
vUp.Normalize(); // Matrix row 1.
vForward.Normalize(); // Matrix row 2.
vGunPos; // Matrix row 3.
But your problem is to look that way slowly.The easiest way is to use linear interpolation:
Vector3 CurrentDirection = /* Get current direction */
Vector3 TargetDirection = /* Get target direction */
float Alpha = 0.5f; // Use smaller values for slower rotations (e.g. based on the weapon weight).
Vector3 NewDirection = ( 1.0f - Alpha ) * CurrentDirection + Alpha * TargetDirection;
This method has exponential decay (e.g. you multiply by 0.5 * 0.5 * 0.5 * ...) and rotates pretty fast against the target direction. A value of Alpha = 0.5 is pretty responsive and snappy which is what you very likely look for. This formula works best with constant time steps. If you have varying time steps you would need to multiply by the ratio of the current and last time step.
I tested some methods lately for something similar and this discrete evolution worked best for me. Though there are other good methods and L. Spiro suggestion will work great as well. I personally liked the exponential decay better than linear error reduction, but this is a matter of personal choice I guess.
HTH,
-Dirk
PS:
In order to update your current rotation you can compute the shortest arc quaternion between the current and new direction:
Quaternion Rotation = ShortestArc( CurrentDirection, NewDirection );
Quaternion NewOrientation = Roation * CurrentOrientation;
Stan Melax wrote a good article about this in Game Programming Gems 1. Google for shortest arc quaternion and you will find some implementations.
@L. Spiro: How do I get pitch, yaw, roll from vRight, vUp, vForward?
How do I calculate the current target based on the gun position and the final target so I can rotate gradually?
#define MAX_UPDATE_DIST 2.0f
Vector vToTarget = (target - currentTarget);
Vector vAmountToMove = vToTarget;
vAmountToMove.Normalize();
vAmountToMove *= fDeltaTime; // * is NOT dot-product, it is a regular per-component scalar multiply.
vAmountToMove *= MAX_UPDATE_DIST; // * is NOT dot-product, it is a regular per-component scalar multiply.
if ( vAmountToMove.LengthSquared() >= vToTarget.LengthSquared() ) {
currentTarget = target;
}
else {
currentTarget += vAmountToMove;
}