Maya, Euler Rotation and Gimbal lock

[illunara]

Hi everybody

I have a question about euler rotation, you will find below the link to an picture

https://ibb.co/gUTd0y

These 2 objects have same local space, rotate-order, position, identical rotation but difference rotate-value, is this a gimbal-lock issues? how can i retrieve the "similify rotate value" (0,0,-122) instead of (180, 180, -60)?

I'm using Maya 2017 Thanks

[AK Eric]

I wouldn't say gimbal lock more as a function of how Euler rotations work within the gimbal system that constrains them:  You can have the exact same "heading" of the local axis between to objects, but they got there by rotating in completely opposite directions.  For example, one rotated with all positive values, and the other rotated with all negative values, but ultimately they keep rotating until they line up.  Or in your case, one rotated -122 on z, while the other spun all over the place to get to the same heading.  Both legit.

You said "identical rotation but difference rotate-value": I'd rephrase that:  "Identical orientations (meaning, same worldspace matrix values), but different rotate values"

[Tuan Nguyen]

Hi Eric

Like you said, i used matrix to calculate data and apply rotation value back to controller. I understand that both values are legit, but is there anything i can do to control the result? How can i know which value i will get after extract data from matrix? or can i convert them vice-versa?

Thanks

On Wed, May 30, 2018 at 1:46 AM, AK Eric <war...@sbcglobal.net> wrote:

I wouldn't say gimbal lock more as a function of how Euler rotations work within the gimbal system that constrains them:  You can have the exact same "heading" of the local axis between to objects, but they got there by rotating in completely opposite directions.  For example, one rotated with all positive values, and the other rotated with all negative values, but ultimately they keep rotating until they line up.  Or in your case, one rotated -122 on z, while the other spun all over the place to get to the same heading.  Both legit.

You said "identical rotation but difference rotate-value": I'd rephrase that:  "Identical orientations (meaning, same worldspace matrix values), but different rotate values"

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[AK Eric]

If you're applying the same worldpsace matrix to two nodes, but they give different rot values yet have the same heading, I would infer that each of the nodes parent's have different orientations, and you're seeing that expressed as different rot values on the two nodes.

[python]

Hi.

I would check also if 'rt_arm_loArm_fk_ctrl' is a joint (with a shape on it), with some rotate axis or joint orient values.

[Tuan Nguyen]

Hi, it's a joint and it has it own values on jointOrientation and rotateAxis. But  when i extract euler-rotation value from MTransformationMatrix, i have switch the rotateOrder match to the target as well.

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[Michael Boon]

Unless I'm mistaken, the Euler rotations (0, 0, -120) and (180,180, 60) are identical for any rotation order.

Having said that, you don't have those. You have roughly (180, 180, -60) for your second one, plus there's an extra 2 degrees in the first one.

I'd be looking at AK Eric's suggestion that the objects are in different parent spaces.