Make acceleration axises consistent

[Eirenliel]

There might be an issue that acceleration axises in packets sent are not matched with rotation axises SlimeVR/SlimeVR-Server#1014 (comment)

This should be true for all trackers, because the rotation is transformed, but not acceleration. But also some IMUs might behave differently and need to be ensured to send acceleration in the same coordinate frame as each other.

It's not a big deal right now, but it will make any future improvements to the system consistent and not stumble over this.

[Eirenliel]

AI SUMBISSIONS OR CODE WILL NOT BE ACCEPTED IN ANY SLIMEVR REPOSITORY. Go away.

[Shade-emry]

in that case i suggest you delete the forked copy of code on your repo that you pulled from my repo

[Eirenliel]

It wasn't accepted @Shade-emry . But sure, it's gone now.

[Shade-emry]

thank you kindly, you were 100% right it was trash

[unlogisch04]

I think that need to be defined more clearly what is needed.

Currently:

• Acceleration is send without gravity.
• IMU_ROTATION is not applied to acceleration

Methoteds / calculation routines used to send the acceleration

• BNO055 imu.getVector(Adafruit_BNO055::VECTOR_LINEARACCEL)
• BNO08x imu.getLinAccel(nAccel.x, nAccel.y, nAccel.z, acc);
• Sensorfusion, BMI160, ICM20948, MPU6050, MPU9250 uses:
  getLinearAccVec or calcLinearAcc(bAxyz, vecGravity, linAccel);

void SensorFusion::calcLinearAcc(
	const sensor_real_t accin[3],
	const sensor_real_t gravVec[3],
	sensor_real_t accout[3]
) {
	accout[0] = accin[0] - gravVec[0] * CONST_EARTH_GRAVITY;
	accout[1] = accin[1] - gravVec[1] * CONST_EARTH_GRAVITY;
	accout[2] = accin[2] - gravVec[2] * CONST_EARTH_GRAVITY;
}

So is the main problem, that the axis are not aligned the same with different IMU_ROTATION?

Also making changes on the tracker, will break it for most of ppl.
So either:

• change the behavior depending on server version/server flags.
• or make that it is behaving like bno with 270 deg as default. And apply the math that way it works on the server, but is not correct for other sensors/defaults.