Unity grab and rotate object

[errorerror]

Hello community!
I've been experimenting on a Desktop app in Unity where I want to grab a cylinder with the Leap Hands
and then rotate it around its center axis. I only want it to be able to rotate around this specific axis and not the other two, like a volume knob, and this rotation will affect the movement of another object in the scene.
I used freeze position property on of the rigidbody for all axes so that it can't move around when the leap hands are moving.
So I tried to do the same for the rotation too, but it doesn't seem to work.
Could you please give me any ideas on how to do that???

Thank you very much in advance.

[errorerror]

Hello again.
I figured out a solution for this problem, I added these few line of code to my interactive object:

        Quaternion objRot = _intObj.rigidbody.rotation;  //_intObj is the interactive object
        Vector3 inEuler = objRot.eulerAngles;
        if (inEuler.y != 0F || inEuler.z != 0.0F)   {
            inEuler.y = 0F;
            inEuler.z = 0F;
            objRot = Quaternion.Euler(inEuler);
            _intObj.rigidbody.rotation = objRot;                 
        }

It seems to be working, so my object only rotates around axis x when I grab it.
The only problem is that it is flckering quite a lot now that its rotation is constrained and I don't know how to change/fix that.
Any ideas would be welcome.
Thanks

[HOTTHANDS]

Hi Errorerror,
Unity3D runs all things in a quaternion sense to avoid gimbal lock that Euler rotations are prone to.
So even when you are using Euler... it is doing some fancy behind the scenes work to translate to quaternions.

I think you are gumming up the works with your attempts to use euler in your code instead of just staying within the quaternions. You my be experiencing a constraint due to gimbal lock which is all about the euler math...

Not sure how much this has changed from 5.6 to 2018.2, but I know that the CSharp has changed for 2018, so code habits may not work as you expect if you are in 2018.... but in 2018 you should be able to handle it all inside quaternions. Please note...It tells you not to mess with the axis rotations unless you are a Hamiltonian pro... It gives you other ways to handle it....

https://docs.unity3d.com/ScriptReference/Quaternion.html

Isolating effects... Leap Motion is a beta... as nice as it is...

So if you're bouncing the Leap Motion Hands along... it might cause your flicker too.

Set it to freely rotate on the x axis with a different input device like a mouse... to isolate Unity3D animation from Leap Hands...

f it works... change the input to the hands... If it didn't work, you know that it is your handling of the rotation physics and the trigger....

good luck

[errorerror]

Hello HOTHANDS and thank you for your response.
I tried to constrain y and z axis rotation by using quaternions, but I think I'm not doing it correctly and I can't figure out why as long as I'm not understanding quaternions quite clearly. I tried using the Quaternion.Set function by keeping the current x and w values and setting the y and z axis values to 0. When I'm using the mouse or keyboard input, as you suggested, everything works fine and the flickering is actually bearly noticeable but when I'm using the leap hands and I grasp my object, I keep getting this error: "Rotation quaternions must be unit length."
I would really appreciate it if you had any other suggestions for me to try or any further explanation.
Thank you, again.

[HOTTHANDS]

First, I think you are incorrect in using zero for any value for quaternions...This video is as conceptual as I have found for explaining how quaternions are different..

You could also contemplate the unit circle as a reference for trigonometry. The radius of the circle is "unit value" aka "1" for the hypotenuse of all inscribed triangles... a zero length hypotenuse would make no sense...

I believe unit value in Unity is a meter. Are your objects set to 1?

So If you are using Leap Motion Tools like Interaction Engine and a simple transform on a Unity cylinder... it should work.
https://leapmotion.github.io/UnityModules/interaction-engine.html#ie-in-depth --- this has some details.

[errorerror]

I'm not sure I completely get quaternions' logic in Unity but I'll take a further look into it and try to better understand it.
Nevertheless thank you very much for your tips and advice.

[sparkoflife10]

Hello errorerror, I want to rotate the GameObject in runtime using the grab (hands) option in Unity. Could you please help me with the code?