modifying joint rotation

Dale Carman

Snap Lens Network Member Lens Studio Team

July 23, 2019 20:13

I want to copy the joint rotation from one bone to another. But I want to give it a smaller value.

so, I am getting the joint rotation by:

var joint1Transform = script.bone1.getWorldTransform();

var joint1Rotation = joint1Transform.getWorldRotation();

var joint2Transform = script.bone2.getWorldTransform();

joint2Transform.setWorldRotation(joint1Rotation);

this works, but how can I half the values? So that if joint 1 has a 30 degree rotation on Z, I put only 15 degrees on joint 2?

thanks,

Dale

1

Mikael Hagen Johansen
Snap Lens Network Member Lens Studio Team

July 23, 2019 20:34
I'm not familiar with joints, but i think this one will help you.

https://lensstudio.snapchat.com/api/classes/quat/

Well, atleast give you ideas.
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Jacob
Snap Lens Network Member Lens Studio Team

July 25, 2019 18:25
Hi Dale,

Working in Euler angles can get messy and inconsistent, so you might have better luck working with quaternions. I'm not totally sure what you want to achieve, but doing something like this will rotate the second joint halfway between the first one and the identity quaternion (which has Euler angles 0,0,0):
```
// @input SceneObject joint1
// @input SceneObject joint2

var tr1 = script.joint1.getTransform();
var tr2 = script.joint2.getTransform();

script.createEvent("UpdateEvent").bind(function(){
    var rot = tr1.getLocalRotation();    
    var newRot = quat.slerp(rot, quat.quatIdentity(), 0.5);    
    tr2.setLocalRotation(newRot);
});
```
Let me know if this works for you!

Jacob
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Dale Carman
Snap Lens Network Member Lens Studio Team

July 25, 2019 19:14
Jacob,

that totally works and is basically where I ended up. Thank you.

thanks,

Dale
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Neha Talreja
Snap Lens Network Member Lens Studio Team

July 26, 2019 20:33
Hi Dale,

Happy to see the Snap community was able to help you out. Please let us know if you need any additional assistance!

Cheers,

Neha
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