I've never looked at the raw data that comes out of the Wii Remote so forgive me for any gaps in knowledge about the subject and I'm sorry if there's someplace else I should have posted this.
However, I DO know that it can determine x, y, z, and roll with just the IR camera and sensor bar. For a regular Wii Remote, that's really all it has to determine those things but a Wii Remote Plus could (and does in some games) it's IMU (gyroscope and accelerometer) to do it's own less-accurate pointing without the sensor bar, so why not do that to fill in gaps in IR camera data?
In short
I'm suggesting that Dolphin provide the option to do IMU pointing while using the sensor bar, screen size, and sensor bar width data as a kind of sync/reference.
Why?
There's about 3 years of games that came out for the Wii before the Wii Remote Plus and Wii MotionPlus were released and, even afterwards, most games still didn't support it. This could enhance those games in a similar way to how a Wii Remote Plus might have.
What exactly would it fix?
I'm assuming sometimes when the Wii Remote is acting kind of erratic it's because the sensor bar is only partially out of view. Sometimes the Wii Remote might only see one tracking point in its view which isn't enough to determine depth and roll. With one sensor point still in view, it can still be used for pointing though and previous known depth and roll could work in conjunction with IMU data to determined/interpolate guess depth and roll in the current frame. When both sensor points are out of view, that's when full IMU pointing would be in use.
Of course, it could also be used as backup for people who have a Wii Remote Plus and no sensor bar at all as long as they have a way of re-centering it.
Why should we care about screen size and sensor bar width?
If Dolphin knows the screen size and sensor bar length then it could theoretically be used along with the last known depth data to determine how sensitive gyro aiming should be. For example, if a player is closer to the sensor bar and they're playing on a larger screen then they will tend to want to tilt the Wii Remote more to point to the edges of the screen. In this case, IMU pointing would be made less sensitive. When they're further away they will tilt the controller less so gyro-pointing sensitivity can be increased.
Now if someone is using a tablet that has a screen the same width as the sensor bar, then they would never tilt the controller all much. That would also be a scenario where someone might prefer to make their own, smaller sensor bar solution since it would more likely that one or no point on a standard sensor bar is in view. If this works correctly, the player wouldn't notice when they've been switched to IMU pointing as long as the controller sees the sensor bar soon afterwards.
Issues
From what I've seen, using accelerometers to try to determine depth even if based off a previous reference would very quickly lead to errors stacking up, so it would probably be best to only try doing that for a few frames and might not be worth doing at all.
However, I DO know that it can determine x, y, z, and roll with just the IR camera and sensor bar. For a regular Wii Remote, that's really all it has to determine those things but a Wii Remote Plus could (and does in some games) it's IMU (gyroscope and accelerometer) to do it's own less-accurate pointing without the sensor bar, so why not do that to fill in gaps in IR camera data?
In short
I'm suggesting that Dolphin provide the option to do IMU pointing while using the sensor bar, screen size, and sensor bar width data as a kind of sync/reference.
Why?
There's about 3 years of games that came out for the Wii before the Wii Remote Plus and Wii MotionPlus were released and, even afterwards, most games still didn't support it. This could enhance those games in a similar way to how a Wii Remote Plus might have.
What exactly would it fix?
I'm assuming sometimes when the Wii Remote is acting kind of erratic it's because the sensor bar is only partially out of view. Sometimes the Wii Remote might only see one tracking point in its view which isn't enough to determine depth and roll. With one sensor point still in view, it can still be used for pointing though and previous known depth and roll could work in conjunction with IMU data to determined/interpolate guess depth and roll in the current frame. When both sensor points are out of view, that's when full IMU pointing would be in use.
Of course, it could also be used as backup for people who have a Wii Remote Plus and no sensor bar at all as long as they have a way of re-centering it.
Why should we care about screen size and sensor bar width?
If Dolphin knows the screen size and sensor bar length then it could theoretically be used along with the last known depth data to determine how sensitive gyro aiming should be. For example, if a player is closer to the sensor bar and they're playing on a larger screen then they will tend to want to tilt the Wii Remote more to point to the edges of the screen. In this case, IMU pointing would be made less sensitive. When they're further away they will tilt the controller less so gyro-pointing sensitivity can be increased.
Now if someone is using a tablet that has a screen the same width as the sensor bar, then they would never tilt the controller all much. That would also be a scenario where someone might prefer to make their own, smaller sensor bar solution since it would more likely that one or no point on a standard sensor bar is in view. If this works correctly, the player wouldn't notice when they've been switched to IMU pointing as long as the controller sees the sensor bar soon afterwards.
Issues
From what I've seen, using accelerometers to try to determine depth even if based off a previous reference would very quickly lead to errors stacking up, so it would probably be best to only try doing that for a few frames and might not be worth doing at all.
