我想在iPhone上创建增强现实视图。作为起点，我看了一下Apple的pARk演示项目。但是，deviceMotion属性用于获取旋转矩阵以进行相机转换。但由于deviceMotion使用陀螺仪（可在iPhone 4及更新版本上使用），我也想支持3GS（实际上，3GS是我唯一的开发设备），我不能使用这种方法。所以我想使用加速度计和指南针提供的数据自己创建旋转矩阵。
不幸的是，我缺乏自己的数学技能。在我周围搜索，this是我的问题最相关的动手指南，但是在实施之后似乎没有适应我的问题（POI视图只是暂时出现而且看似更多由于设备移动而不是其标题;我已经发布了我的onDisplayLink方法（唯一有重大变化的方法）。我已经尝试阅读相关的数学，但是在这一点上，我根本不了解它自己找到一个方法或者在我的代码中找到错误。有什么帮助吗？
编辑：我已经认识到传感器数据应该更好地存储在双精度数据中而不是整数存储中，并添加了一些平滑处理。现在我可以更清楚地看到在设备旋转时应该从侧面出现的POI是如何从上方下降的。也许这有助于指出什么是错的。
CMAccelerometerData* orientation = motionManager.accelerometerData;
CMAcceleration acceleration = orientation.acceleration;
vec4f_t normalizedAccelerometer;
vec4f_t normalizedMagnetometer;
xG = (acceleration.x * kFilteringFactor) + (xG * (1.0 - kFilteringFactor));
yG = (acceleration.y * kFilteringFactor) + (yG * (1.0 - kFilteringFactor));
zG = (acceleration.z * kFilteringFactor) + (zG * (1.0 - kFilteringFactor));
xB = (heading.x * kFilteringFactor) + (xB * (1.0 - kFilteringFactor));
yB = (heading.y * kFilteringFactor) + (yB * (1.0 - kFilteringFactor));
zB = (heading.z * kFilteringFactor) + (zB * (1.0 - kFilteringFactor));
double accelerometerMagnitude = sqrt(pow(xG, 2) + pow(yG, 2) + pow(zG, 2));
double magnetometerMagnitude = sqrt(pow(xB, 2) + pow(yB, 2) + pow(zB, 2));
normalizedAccelerometer[0] = xG/accelerometerMagnitude;
normalizedAccelerometer[1] = yG/accelerometerMagnitude;
normalizedAccelerometer[2] = zG/accelerometerMagnitude;
normalizedAccelerometer[3] = 1.0f;
normalizedMagnetometer[0] = xB/magnetometerMagnitude;
normalizedMagnetometer[1] = yB/magnetometerMagnitude;
normalizedMagnetometer[2] = zB/magnetometerMagnitude;
normalizedMagnetometer[3] = 1.0f;
vec4f_t eastDirection;
eastDirection[0] = normalizedAccelerometer[1] * normalizedMagnetometer[2] - normalizedAccelerometer[2] * normalizedMagnetometer[1];
eastDirection[1] = normalizedAccelerometer[0] * normalizedMagnetometer[2] - normalizedAccelerometer[2] * normalizedMagnetometer[0];
eastDirection[2] = normalizedAccelerometer[0] * normalizedMagnetometer[1] - normalizedAccelerometer[1] * normalizedMagnetometer[0];
eastDirection[3] = 1.0f;
double eastDirectionMagnitude = sqrt(pow(eastDirection[0], 2) + pow(eastDirection[1], 2) + pow(eastDirection[2], 2));
vec4f_t normalizedEastDirection;
normalizedEastDirection[0] = eastDirection[0]/eastDirectionMagnitude;
normalizedEastDirection[1] = eastDirection[1]/eastDirectionMagnitude;
normalizedEastDirection[2] = eastDirection[2]/eastDirectionMagnitude;
normalizedEastDirection[3] = 1.0f;
vec4f_t northDirection;
northDirection[0] = (pow(normalizedAccelerometer[0], 2) + pow(normalizedAccelerometer[1],2) + pow(normalizedAccelerometer[2],2)) * xB - (normalizedAccelerometer[0] * xB + normalizedAccelerometer[1] * yB + normalizedAccelerometer[2] * zB)*normalizedAccelerometer[0];
northDirection[1] = (pow(normalizedAccelerometer[0], 2) + pow(normalizedAccelerometer[1],2) + pow(normalizedAccelerometer[2],2)) * yB - (normalizedAccelerometer[0] * xB + normalizedAccelerometer[1] * yB + normalizedAccelerometer[2] * zB)*normalizedAccelerometer[1];
northDirection[2] = (pow(normalizedAccelerometer[0], 2) + pow(normalizedAccelerometer[1],2) + pow(normalizedAccelerometer[2],2)) * zB - (normalizedAccelerometer[0] * xB + normalizedAccelerometer[1] * yB + normalizedAccelerometer[2] * zB)*normalizedAccelerometer[2];
northDirection[3] = 1.0f;
double northDirectionMagnitude;
northDirectionMagnitude = sqrt(pow(northDirection[0], 2) + pow(northDirection[1], 2) + pow(northDirection[2], 2));
vec4f_t normalizedNorthDirection;
normalizedNorthDirection[0] = northDirection[0]/northDirectionMagnitude;
normalizedNorthDirection[1] = northDirection[1]/northDirectionMagnitude;
normalizedNorthDirection[2] = northDirection[2]/northDirectionMagnitude;
normalizedNorthDirection[3] = 1.0f;
CMRotationMatrix r;
r.m11 = normalizedEastDirection[0];
r.m21 = normalizedEastDirection[1];
r.m31 = normalizedEastDirection[2];
r.m12 = normalizedNorthDirection[0];
r.m22 = normalizedNorthDirection[1];
r.m32 = normalizedNorthDirection[2];
r.m13 = normalizedAccelerometer[0];
r.m23 = normalizedAccelerometer[1];
r.m33 = normalizedAccelerometer[2];
transformFromCMRotationMatrix(cameraTransform, &r);
[self setNeedsDisplay];
当设备放在桌子上并且大致（使用Compass.app）指向北方时，我会记录这些数据：
Accelerometer: x: -0.016692, y: 0.060852, z: -0.998007
Magnetometer: x: -0.016099, y: 0.256711, z: -0.966354
North Direction x: 0.011472, y: 8.561041, z:0.521807
Normalized North Direction x: 0.001338, y: 0.998147, z:0.060838
East Direction x: 0.197395, y: 0.000063, z:-0.003305
Normalized East Direction x: 0.999860, y: 0.000319, z:-0.016742
这看起来是否合理？
编辑2：我已经将r的分配更新为显然导致我达到目标的一个：当设备正常时，我现在看到水平面附近的地标;然而，它们距离预期位置约90º时钟。此外，Beta建议的移动后的输出：
Accelerometer: x: 0.074289, y: -0.997192, z: -0.009475
Magnetometer: x: 0.031341, y: -0.986382, z: -0.161458
North Direction x: -1.428996, y: -0.057306, z:-5.172881
Normalized North Direction x: -0.266259, y: -0.010678, z:-0.963842
East Direction x: 0.151658, y: -0.011698, z:-0.042025
Normalized East Direction x: 0.961034, y: -0.074126, z:-0.266305
答案 0 :(得分：2)
在掌握了iPhone 4后，我能够将上面代码生成的数据与CoreMotion态度数据的输出进行比较。有了这个，我发现我应该按照以下方式将值分配给我的旋转矩阵：
CMRotationMatrix r;
r.m11 = normalizedNorthDirection[0];
r.m21 = normalizedNorthDirection[1];
r.m31 = normalizedNorthDirection[2];
r.m12 = 0 - normalizedEastDirection[0];
r.m22 = normalizedEastDirection[1];
r.m32 = 0 - normalizedEastDirection[2];
r.m13 = 0 - normalizedAccelerometer[0];
r.m23 = 0 - normalizedAccelerometer[1];
r.m33 = 0 - normalizedAccelerometer[2];
这给出了大致相似的值，但当然CoreMotion使用陀螺仪产生的数据要好得多。无论如何，这是合理支持3GS的起点。也许通过某种过滤可以获得额外的质量，但我还没有决定是否值得付出努力。