# Center of rotation

Correcting the generated motion relative to the center of gravity.

Most games, send data relative to the center of gravity of the simulated vehicle.
So , if you think of a plane, the CG is usually in the wings, and if you are piloting a comercial airliner, you are probably sitting 14m ahead of the CG.

So the data we receive, is relative to the CG, making rotations and accelerations relative to CG.
Sitting so far of the CG, requires us to correct that data, to get the correct motion cues.
Take a look at the figures:

On the left you have the pilot on the CG, so the felt rotation is really a rotation.
On the right, the pilot is sitting way ahead of the CG, and a rotation, is not just a rotation, it's also a lateral and longitudinal acceleration due to the centripetal acceleration.
The far you are, less you feel the rotation, and what you feel is more like linear accelerations.

To correct this, Mover allows you to do it in three modules:

# COR correction in the source

Here is the correct place for big displacements.
Ideal for big airliners or others with distances above 1 meter.

On the right figure we can see in the source options, the controls to define the position of the pilot.
You set the distance in sway, surge and heave directions (meters).
XPlane 11 gives us the pilot position, so it's an extra option compared to the other sources.

Besides the position, you can also define a filter to smooth the results, since the calculations can have some noise incorporated.

The COR correction is not present in all the sources. This is because to make it, we need to have the longitudinal and rotational accelerations.
So if we are missing data, the COR correction is not available.
When calculation is performed, linear accelerations are incremented with the effects of the centripetal accelerations.
Same for linear speeds. They are correct for the new position.

In the air crafts example above, this is specially noticeable on the runaway taxing.

# COR correction in the rig

To correct small displacements.
Rig correction might be enough for cars, but prefer the source to do it if any distance exceeds 1 meter.

The position value is changed in the marked fields on the right image, and values are in milimeters.

If you have the 3D view enabled, you can see the center of rotation moving when you change the value.

# COR correction in the pose

Use to cheat rotations and increase a specific effect.

It's not suitable for pilot/driver position correction. Possible for short distances, but not recommendable since it acts just on the pose result.

We use this COR correction to change the center of rotation independently for each one of the rotational DOF in that pose.

So, you can change the sway an surge location of the center of yaw, the surge and heave for the center of pitch or the sway and heave of the roll. That's why some of the fields are locked, since they have no effect in that rotation DOF.

So, for example, use this to increase the effect of traction loss, putting the yaw COR at the front of the rig. This way, you feel the rig rotating at the front, not at it's center.

This works by adjusting linear DOF in the rig. If you change the yaw center to the front and make a yaw rotation the calculation is going to introduce sway and surge to correct the rig to turn around the pretended location.