Iphone 如何创建新的Cmatitude参考坐标系，使重力位于Y轴上

我希望能够更改设备运动管理器参考帧（用于陀螺仪），以便使重力向量位于Y轴上

通常，在启动设备运动管理器更新时，手机的z轴仅与重力对齐

您可以将其更改为使用磁强计使x轴与磁极或真北极对齐。这样我的X轴指向北方，Z轴指向下方

我想做的是让我的Y轴（负）指向下（这样它就与重力对齐），同时让我的X轴指向真正的磁极

我想要的结果是，当我的手机在垂直（纵向）方向上静止不动时，手机的右侧将与北极对齐，我的所有读数（滚动、俯仰、偏航）都将读取为0。然后，如果我在X轴上旋转手机，俯仰就会改变，如果我绕Y轴旋转，偏航就会改变

到目前为止，我知道我可以设置自己的参考坐标系，如果我乘以之前存储的姿态的倒数，（就像我可以手动将手机设置为这个方向，保存该姿态，然后继续将新姿态乘以存储姿态的倒数，我所有的读数都将与我想要的完全相同）

但是手动设置它不是一个选项，那么如何通过编程实现呢

我不认为有一个函数可以创建我自己的姿态参考系，或者如果至少有一个函数可以将姿态乘以旋转矩阵，那么我可能可以解决这个问题。（因为我会把所有的姿态乘以音高的90度变化）

我希望我解释清楚

如有任何建议，我将不胜感激。谢谢

PD：这些是iPhone的方向坐标：

可以更改CMAttitude实例使用的参考帧。为此，缓存包含该参考帧的姿态对象，并将其作为参数传递给multiplyByInverseOfAttitude:。接收信息的姿态参数将更改，以表示来自该参考系的姿态变化

<> P>看看这有什么用，考虑一个棒球游戏，用户旋转设备摆动。通常，在球场开始时，球棒会处于某个静止方向。在那之后，球棒将在一个方向上被渲染，这个方向是由设备的姿态如何从一个球开始时的位置改变而决定的

-(void) startPitch {

// referenceAttitude is an instance variable

referenceAttitude = [motionManager.deviceMotion.attitude retain];

}

}

要了解更多信息，请查看下面的链接，该链接与您想要的内容相同

伪代码：

启动设备运动更新

在背景中启动摄影机预览；）

捕获设备当前的重力读数作为C加速度。。。一旦你有重力，把它存储在一个局部变量中

然后你必须取两个向量，得到它们之间的角度，在这种情况下，设备重力为（0,0，-1）和真实重力向量

然后我们把θ变成θ。。。与CoreMotion参考方向匹配的变换

设置计时器以设置动画

在动画期间，获取motionManager的deviceMotion属性的旋转矩阵的倒数

以正确的顺序应用变换以反映设备的当前姿态（欧拉模式下的偏航、俯仰、滚动或设备四元数旋转…基本上用3种不同的方式表示相同的事情）

代码如下：

- (void) initMotionCapture
{
    firstGravityReading = NO;
    referenceAttitude = nil;

    if (motionManager == nil)
    {
        self.motionManager = [CMMotionManager new];
    }
    motionManager.deviceMotionUpdateInterval = 0.01;
    self.gravityTimer = [NSTimer scheduledTimerWithTimeInterval:1/60.0 
                                 target:self 
                                 selector:@selector(getFirstGravityReading) 
                                 userInfo:nil repeats:YES];
}


- (void) getFirstGravityReading
{
    CMAcceleration currentGravity; 

    CMDeviceMotion *dm = motionManager.deviceMotion;
    referenceAttitude = dm.attitude;
    currentGravity = dm.gravity;

    [motionManager startDeviceMotionUpdates];

    if (currentGravity.x !=0 && 
        currentGravity.y !=0 && currentGravity.z !=0)
    {
        NSLog(@"Gravity = (%f,%f,%f)", 
              currentGravity.x, currentGravity.y, currentGravity.z);

        firstGravityReading = YES;
        [gravityTimer invalidate];
        self.gravityTimer = nil;
        [self setupCompass];
    }
}

- (void) setupCompass
{
    //Draw your cube... I am using a quartz 3D perspective hack!
    CATransform3D initialTransform = perspectiveTransformedLayer.sublayerTransform;
    initialTransform.m34 = 1.0/-10000;


    //HERE IS WHAT YOU GUYS NEED... the vector equations!
    NSLog(@"Gravity = (%f,%f,%f)", 
          currentGravity.x, currentGravity.y, currentGravity.z);

    //we have current gravity vector and our device gravity vector of (0, 0, -1)
    // get the dot product
    float dotProduct = currentGravity.x*0 + 
                       currentGravity.y*0 + 
                       currentGravity.z*-1;
    float innerMagnitudeProduct = currentGravity.x*currentGravity.x + 
                                  currentGravity.y + currentGravity.y + 
                                  currentGravity.z*currentGravity.z;
    float magnitudeCurrentGravity = sqrt(innerMagnitudeProduct);
    float magnitudeDeviceVector = 1; //since (0,0,-1) computes to: 0*0 + 0*0 + -1*-1 = 1

    thetaOffset = acos(dotProduct/(magnitudeCurrentGravity*magnitudeDeviceVector));
    NSLog(@"theta(degrees) = %f", thetaOffset*180.0/M_PI);

    //Now we have the device angle to the gravity vector (0,0,-1)
    //We must transform these coordinates to match our 
    //device's attitude by transforming to theta prime
    float theta_deg = thetaOffset*180.0/M_PI;
    float thetaPrime_deg = -theta_deg + 90; // ThetaPrime = -Theta + 90 <==> y=mx+b

    NSLog(@"thetaPrime(degrees) = %f", thetaOffset*180.0/M_PI);

    deviceOffsetRotation = 
        CATransform3DMakeRotation((thetaPrime_deg) * M_PI / 180.0, 1, 0, 0);
    initialTransform = CATransform3DConcat(deviceOffsetRotation, initialTransform);

    perspectiveTransformedLayer.sublayerTransform = initialTransform;

    self.animationTimer = [NSTimer scheduledTimerWithTimeInterval:1/60.0 
                                   target:self 
                                   selector:@selector(tick) 
                                   userInfo:nil 
                                   repeats:YES];

}

- (void) tick
{
    CMRotationMatrix rotation;

    CMDeviceMotion *deviceMotion = motionManager.deviceMotion;
    CMAttitude *attitude = deviceMotion.attitude;

    if (referenceAttitude != nil)
    {
        [attitude multiplyByInverseOfAttitude:referenceAttitude];
    }
    rotation = attitude.rotationMatrix;

    CATransform3D rotationalTransform = perspectiveTransformedLayer.sublayerTransform;

    //inverse (or called the transpose) of the attitude.rotationalMatrix
    rotationalTransform.m11 = rotation.m11;
    rotationalTransform.m12 = rotation.m21;
    rotationalTransform.m13 = rotation.m31;

    rotationalTransform.m21 = rotation.m12;
    rotationalTransform.m22 = rotation.m22;
    rotationalTransform.m23 = rotation.m32;

    rotationalTransform.m31 = rotation.m13;
    rotationalTransform.m32 = rotation.m23;
    rotationalTransform.m33 = rotation.m33;

    rotationalTransform = 
        CATransform3DConcat(deviceOffsetRotation, rotationalTransform);
    rotationalTransform = 
        CATransform3DConcat(rotationalTransform, 
                            CATransform3DMakeScale(1.0, -1.0, 1.0));


    perspectiveTransformedLayer.sublayerTransform = rotationalTransform;
}

-（void）initMotionCapture
{
firstGravityReading=否；
参考态度=零；
如果（motionManager==nil）
{
self.motionManager=[CMMotionManager new]；
}
motionManager.deviceMotionUpdateInterval=0.01；
self.gravitymer=[NSTimer scheduledTimerWithTimeInterval:1/60.0
目标：自我
选择器：@selector（getFirstGravityReading）
userInfo:nil repeats:YES]；
}
-（无效）getFirstGravityReading
{
c加速度；重力；
CMDeviceMotion*dm=motionManager.deviceMotion；
参考态度=dm.态度；
当前重力=dm.gravity；
[motionManager StartDeviceMotionUpdate]；
如果（currentGravity.x！=0&&
currentGravity.y！=0&¤tGravity.z！=0）
{
NSLog（@“重力=（%f，%f，%f）”，
currentGravity.x，currentGravity.y，currentGravity.z）；
firstGravityReading=是；
[gravityTimer失效]；
self.gravitymer=nil；
[自我设置指南针]；
}
}
-（无效）指南针
{
//画你的立方体…我正在使用石英三维透视黑客！
CATTransformM3D initialTransform=透视转换层。子层转换；
initialTransform.m34=1.0//-10000；
//这是你们需要的…向量方程！
NSLog（@“重力=（%f，%f，%f）”，
currentGravity.x，currentGravity.y，currentGravity.z）；
//我们有当前重力向量和我们的设备重力向量（0，0，-1）
//得到点积
浮点点积=currentGravity.x*0+
当前重力.y*0+
电流重力z*-1；
float innerMagnitudeProduct=currentGravity.x*currentGravity.x+
currentGravity.y+currentGravity.y+
currentGravity.z*currentGravity.z；
浮动幅度CurrentGravity=sqrt（内部幅度乘积）；
float magnityDeviceVector=1；//因为（0,0，-1）计算为：0*0+0*0+-1*-1=1
thetaOffset=acos（点积/（震级当前重力*震级设备向量））；
NSLog（@“θ（度）=%f”，θ偏移*180.0/M_π）；
//现在我们有了设备与重力向量的角度（0,0，-1）
//我们必须变换这些坐标以匹配我们的
//通过转换为θ素数的设备姿态
浮动西塔德
- (void) initMotionCapture
{
    firstGravityReading = NO;
    referenceAttitude = nil;

    if (motionManager == nil)
    {
        self.motionManager = [CMMotionManager new];
    }
    motionManager.deviceMotionUpdateInterval = 0.01;
    self.gravityTimer = [NSTimer scheduledTimerWithTimeInterval:1/60.0 
                                 target:self 
                                 selector:@selector(getFirstGravityReading) 
                                 userInfo:nil repeats:YES];
}


- (void) getFirstGravityReading
{
    CMAcceleration currentGravity; 

    CMDeviceMotion *dm = motionManager.deviceMotion;
    referenceAttitude = dm.attitude;
    currentGravity = dm.gravity;

    [motionManager startDeviceMotionUpdates];

    if (currentGravity.x !=0 && 
        currentGravity.y !=0 && currentGravity.z !=0)
    {
        NSLog(@"Gravity = (%f,%f,%f)", 
              currentGravity.x, currentGravity.y, currentGravity.z);

        firstGravityReading = YES;
        [gravityTimer invalidate];
        self.gravityTimer = nil;
        [self setupCompass];
    }
}

- (void) setupCompass
{
    //Draw your cube... I am using a quartz 3D perspective hack!
    CATransform3D initialTransform = perspectiveTransformedLayer.sublayerTransform;
    initialTransform.m34 = 1.0/-10000;


    //HERE IS WHAT YOU GUYS NEED... the vector equations!
    NSLog(@"Gravity = (%f,%f,%f)", 
          currentGravity.x, currentGravity.y, currentGravity.z);

    //we have current gravity vector and our device gravity vector of (0, 0, -1)
    // get the dot product
    float dotProduct = currentGravity.x*0 + 
                       currentGravity.y*0 + 
                       currentGravity.z*-1;
    float innerMagnitudeProduct = currentGravity.x*currentGravity.x + 
                                  currentGravity.y + currentGravity.y + 
                                  currentGravity.z*currentGravity.z;
    float magnitudeCurrentGravity = sqrt(innerMagnitudeProduct);
    float magnitudeDeviceVector = 1; //since (0,0,-1) computes to: 0*0 + 0*0 + -1*-1 = 1

    thetaOffset = acos(dotProduct/(magnitudeCurrentGravity*magnitudeDeviceVector));
    NSLog(@"theta(degrees) = %f", thetaOffset*180.0/M_PI);

    //Now we have the device angle to the gravity vector (0,0,-1)
    //We must transform these coordinates to match our 
    //device's attitude by transforming to theta prime
    float theta_deg = thetaOffset*180.0/M_PI;
    float thetaPrime_deg = -theta_deg + 90; // ThetaPrime = -Theta + 90 <==> y=mx+b

    NSLog(@"thetaPrime(degrees) = %f", thetaOffset*180.0/M_PI);

    deviceOffsetRotation = 
        CATransform3DMakeRotation((thetaPrime_deg) * M_PI / 180.0, 1, 0, 0);
    initialTransform = CATransform3DConcat(deviceOffsetRotation, initialTransform);

    perspectiveTransformedLayer.sublayerTransform = initialTransform;

    self.animationTimer = [NSTimer scheduledTimerWithTimeInterval:1/60.0 
                                   target:self 
                                   selector:@selector(tick) 
                                   userInfo:nil 
                                   repeats:YES];

}

- (void) tick
{
    CMRotationMatrix rotation;

    CMDeviceMotion *deviceMotion = motionManager.deviceMotion;
    CMAttitude *attitude = deviceMotion.attitude;

    if (referenceAttitude != nil)
    {
        [attitude multiplyByInverseOfAttitude:referenceAttitude];
    }
    rotation = attitude.rotationMatrix;

    CATransform3D rotationalTransform = perspectiveTransformedLayer.sublayerTransform;

    //inverse (or called the transpose) of the attitude.rotationalMatrix
    rotationalTransform.m11 = rotation.m11;
    rotationalTransform.m12 = rotation.m21;
    rotationalTransform.m13 = rotation.m31;

    rotationalTransform.m21 = rotation.m12;
    rotationalTransform.m22 = rotation.m22;
    rotationalTransform.m23 = rotation.m32;

    rotationalTransform.m31 = rotation.m13;
    rotationalTransform.m32 = rotation.m23;
    rotationalTransform.m33 = rotation.m33;

    rotationalTransform = 
        CATransform3DConcat(deviceOffsetRotation, rotationalTransform);
    rotationalTransform = 
        CATransform3DConcat(rotationalTransform, 
                            CATransform3DMakeScale(1.0, -1.0, 1.0));


    perspectiveTransformedLayer.sublayerTransform = rotationalTransform;
}