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PORotating Accelerometer output to new "neutral" for iOS, (and others).
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copied!<p>what i have here works exactly how i want it. My question is that it seems overly complex, is there a faster/better way of doing the pitchAngleRadians calculations i am showing below?</p> <p>the code is shown... (along with two images)</p> <p>the first image is how the atan2 calculation comes out of the iPad naturally, "pitchAngleRadians = atan2(accel[0], accel<a href="https://i.stack.imgur.com/Cij73.png" rel="nofollow noreferrer">2</a>);" (what the accelerometer puts out normally) </p> <p>what i want is to shift "Zero" to a new degree angle, in the second image i've shifted it a -135 degrees as an example. (everything in code is radians) so for instance the variable "pitchNeutralAngle" in this example is the radian equivalent of (-135) degrees</p> <p>this code produces exactly what i want for the variable "pitchAngleRadians", which is the second image, but seems too long, and this code is in a tight run loop, so it would speed up if i can get this cleaner/faster.</p> <p>i go through an intermediate step of "ranging" the degrees between 0 and 360, so that crossing the boarder of 180 degrees does not mess up the calculation, however i still have to get it back to the 0 to 180 form, so that is what the next calculation is.</p> <p>i've tested this code a little bit, and it does appear to work.</p> <pre><code>//------------------------------------------------------------------------------------ - (void)accelerometer:(UIAccelerometer*)accelerometer didAccelerate:(UIAcceleration*)acceleration { accel[0] = (acceleration.x * kFilteringFactor) + accel[0] * (1.0 - kFilteringFactor); accel[1] = (acceleration.y * kFilteringFactor) + accel[1] * (1.0 - kFilteringFactor); accel[2] = (acceleration.z * kFilteringFactor) + accel[2] * (1.0 - kFilteringFactor); pitchAngleRadians = (atan2(accel[0], accel[2]) - pitchNeutralAngle); pitchAngleRadians = pitchAngleRadians - floorf(pitchAngleRadians/6.28318f)*6.28318f; if (pitchAngleRadians > 3.14159) pitchAngleRadians = -6.28318f + pitchAngleRadians; //float a = atan2(accel[0], accel[2]); //NSLog(@"a = %f", a); } </code></pre> <p><img src="https://i.stack.imgur.com/jDHYD.png" alt="naturally comes out of the accelerometer"></p> <p><img src="https://i.stack.imgur.com/Cij73.png" alt="after re-"neutralizing" zero angle"></p>

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