Rotate single axis of object to nearest 90 degrees

Question

I'm working on a 6 DOF game, so I have a character that flies around, with mouselook, and rotates properly.

What I want to do now, is if the player isn't rolling (by pressing Q and E), I want to "correct" the roll of the quaternion to the nearest 90 degree angle (so the s$$anonymous$$p levels itself). So, I guess I want to modify the rotation, along the transform.forward axis, to go to the next increment of 90.

It's easy to do if I just modify the eulerAngles, but it doesn't quite have the effect I want - it doesn't take into account the forward vector, so as soon as you turn upside down or at a strange angle, it freaks out and doesn't rotate properly.

Here is what I have now:

     private void HandleMouseLook()
     {
         float mouseInputX = Input.GetAxis("Mouse X") * mouseSensitivityX;
         float mouseInputY = -Input.GetAxis("Mouse Y") * mouseSensitivityY;
         float rollInput = Input.GetAxis("Roll") * rollSpeed; // Roll is Q and E keys
 
         var rotation = new Vector3(mouseInputY, mouseInputX, rollInput) * Time.deltaTime;
         S$$anonymous$$pComponent.RigidbodyComponent.AddRelativeTorque(rotation);

         // If rollInput == 0.0f, correct rotation along transform.forward axis to nearest 90 degrees
     }

Answer 1

Answer by FlaSh-G · Jun 23, 2017 at 07:35 AM

I'd recommend splitting your GameObject into two, and making one of them the parent of the other.

The parent GO would handle the mouse look rotation you already have, w$$anonymous$$le the c$$anonymous$$ld rolls relatively to it. The c$$anonymous$$ld also contains the model, so both rotations get combined for it. Moving the c$$anonymous$$ld's local rotation towards the nearest 90 degree step is rather easy.

Now you can choose: Does rolling affect how the mouse look rotation works, or is it rather just a visual t$$anonymous$$ng? If it's just visual, you can stop here. If not, you will have to read the c$$anonymous$$ld's local rotation and modify your mouse look rotation vector in the parent's script accordingly. Transform.TransformDirection will probably help there.

 var rotation = new Vector3(mouseInputY, mouseInputX, 0);
 transform.TransformDirection(rotation);
 S$$anonymous$$pComponent.RigidbodyComponent.AddRelativeTorque(rotation* Time.deltaTime);

I haven't tested t$$anonymous$$s, but it should give you a direction to go for.

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Dooskington · Jun 24, 2017 at 01:19 AM 0

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Unfortunately this doesn't really work.

It works until the player turns upside down, or at a steep angle - then it starts freaking out. I've tried messing with transform.TransformDirection, but it doesn't seem to do what I want. I think I need a quaternion solution, as it will account for the strange steep angles of the parent object.

FlaSh-G Dooskington · Jun 24, 2017 at 10:36 AM 0

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Maybe this related question helps you.

Dooskington FlaSh-G · Jun 24, 2017 at 08:21 PM 0

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FlaSh-G,

It kind of did! I almost have it. On my child component (the camera), I am doing this now:

         Quaternion rotation = Quaternion.LookRotation(transform.parent.forward, transform.parent.up);
         Vector3 euler = rotation.eulerAngles;
         euler.z = 0.0f;
 
         transform.rotation = Quaternion.Euler(euler);

This seems to keep it correct, while in a normal orientation - but I'm still getting the same issue when I turn upside down, or straight vertically. The definition of it's Z axis seems to change and it just spins around trying to snap itself to 0.

Rotate single axis of object to nearest 90 degrees

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