CODEWITHSUNDEEP
c#unity-game-engine3drotationquaternions
Mkoch
Mkoch

Reputation: 2024

Off-center rotate object in Unity

I have a laser turret in Unity3D, which I'd like to turn towards the enemies. The turret consists of a "leg" and a "head" (selected on the picture 1). The head can pan and tilt around a spherical joint.

I do the following: 

    Vector3 targetDir = collision.gameObject.transform.position - turretHead.transform.position;
    float step = turnSpeed * Time.deltaTime;
    Vector3 newDir = Vector3.RotateTowards(turretHead.transform.forward, targetDir, step, 0.0f);
    turretHead.transform.rotation = Quaternion.LookRotation(newDir);

The problem is that since the pivot of the head is not aligned with the laser beam, the turret turns into the almost right direction, but it shoots above the target. (It would hit perfectly, if the laser would come out of the red axis of the pivot.)

Is there a builtin method or some trick to achieve the correct functionality other then doing the calculation myself?

Turret

Upvotes: 1

Views: 728

Answers (1)

Louis Ingenthron
Louis Ingenthron

Reputation: 1368

Okay, here's the quick and easy way to do this. It's probably "better" to do it with proper trig, but this should give you the result you want pretty quick:

If you don't already have a transform aligned with the barrel, then create an empty GameObject and line it up (make sure it's a child of the turret so they move together). Add a reference to your script for it's transform.

Then, in your first line, calculate from the new Barrel transform instead of the turretHead transform. Leave everything else the same. This way it calculates from the turret barrel, but moves the turret head.

Now, this approach isn't perfect. If the pivot center is too offset from the barrel transform, then it would be less accurate over large moves, or when aiming at something close by, because the expected position when aiming would be different than the initial position due to the rotation pivot being elsewhere. But this can be solved with iteration, as the calculation would become more accurate the closer it is to it's desired goal.

Upvotes: 1

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