Flip ONE axis of Quaternion ( from right to left handed coordinae system)

Question

There are a lot of similar questions, but I can't find the answer =(. I get a quaternion from the sensor in right hand coordinate system. Then I draw an object in the Unity by this quaternion. Unity uses left handed cordinate system. And if I rotate sensor clockwise by one axis, one axis will always rotate in the opposite direction =( I've read a lot of books, articles, forums posts for about 3 weeks. And I still can't find a solution.

I've tested follow algorithms: 1. Convert quaternion to matrix -> then convert matrix to left handed CS ( determinaте will be -1) -> and convert back to quaternion - this doesn't work.

Transformation matrix (3x3) = 1 0 0 0 1 0 0 1 -1

Matrix in new CS = (Transformation matrix)(q_mat)(Transformation matrix)

Flip two component of quaternion also will save right CS. It will flip two axis.

And a lot of other methods.... Please help =(((

score 3 · Answer 1 · answered Aug 08 '17 at 15:00

3

If you want to convert right-handed coordinate to Unity's left handed coordinate, use the function below:

private Quaternion rightCoordToUnityCord(Quaternion q)
{
    return new Quaternion(q.x, q.y, -q.z, -q.w);
}

It came from Unity's doc and I've been using it since I found it. Hopefully it will solve your problem.

answered Aug 08 '17 at 15:00

Programmer

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I did it, it' will swop X and Y and save right handed CS – Arthur Aug 08 '17 at 15:04
Unfortunately no/ This method change rotation of two axis and now all three axis give rotation in opposite direction. – Arthur Aug 08 '17 at 15:12
Are you sure? What's/Where is the input of the right-handed coordinate? – Programmer Aug 08 '17 at 15:13
Yes. Without changes only Z axis give opposite direction. After return new Quaternion(q.x, q.y, -q.z, -q.w); All three axis has opposite direction. – Arthur Aug 08 '17 at 15:15
Quternion from sensor in the right handed coordinate. – Arthur Aug 08 '17 at 15:19
From accelerometer/gyro sensor? – Programmer Aug 08 '17 at 15:21
It's complicated sensor, with acc, gyro, mag and MCU on board, and return data are quaternion of orientation in right handed CS. – Arthur Aug 08 '17 at 15:35
This should work. I don't know why it's not working for you. Can you try `Quaternion.Inverse`? That should give you the left handed coords too, – Programmer Aug 08 '17 at 23:12

Flip ONE axis of Quaternion ( from right to left handed coordinae system)

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