从 CoreMotion 的姿态旋转矩阵中隔离并移除水平旋转

Question

我正在制作类似增强现实应用程序的东西，其中有一个 OpenGL 场景，无论 iOS 设备如何移动，我都希望它与重力保持一致。我以为我已经用 CMDeviceMotion.attitude.pitch 设置得很好，直到我发现将 iPhone 侧向倾斜会扰乱该数字。因此，我从 pARk* 示例中获取了一些代码，现在我正在尝试隔离围绕垂直访问的旋转。我正在绘制的场景并不关心用户面向哪个方向，人物将始终与观看者保持一定的距离。我认为，当我计算出垂直轴旋转分量时，我可以将其反转并将其与旋转矩阵相乘，以便在用户更改标题时保持 OpenGL 图形静止。

这是我的代码：

CMDeviceMotion *d = motionManager.deviceMotion;
if (d != nil) {

    CMRotationMatrix r = d.attitude.rotationMatrix;
    transformFromCMRotationMatrix(cameraTransform, &r);


    mat4f_t projectionCameraTransform;
    multiplyMatrixAndMatrix(projectionCameraTransform, projectionTransform, cameraTransform);

    GLKMatrix4 rotMatrix = GLKMatrix4Make(projectionCameraTransform[0], 
                                          projectionCameraTransform[1], 
                                          projectionCameraTransform[2], 
                                          projectionCameraTransform[3], 
                                          projectionCameraTransform[4], 
                                          projectionCameraTransform[5], 
                                          projectionCameraTransform[6], 
                                          projectionCameraTransform[7], 
                                          projectionCameraTransform[8], 
                                          projectionCameraTransform[9], 
                                          projectionCameraTransform[10], 
                                          projectionCameraTransform[11], 
                                          projectionCameraTransform[12], 
                                          projectionCameraTransform[13], 
                                          projectionCameraTransform[14], 
                                          projectionCameraTransform[15]);

    }

然后我像往常一样在 OpenGL 中使用 rotMatrix。

想法、建议？提前致谢。

*公园示例代码在真实空间中设置了几个点，计算出用户的位置和这些点的相对方向，并将它们绘制在屏幕上，以便它们看起来漂浮在指向其位置的地平​​线上。

Answer 1

我只是根据设备屏幕方向绕 Z 轴旋转方向。这不是最漂亮的，但它似乎完全符合我的需要，无需去欧拉和返回（因此，避免了健身房锁问题）

GLKMatrix4 deviceMotionAttitudeMatrix;
if (_cmMotionmanager.deviceMotionActive) {
    CMDeviceMotion *deviceMotion = _cmMotionmanager.deviceMotion;

    // Correct for the rotation matrix not including the screen orientation:
    // TODO: Let the device notify me when the orientation changes instead of querying on each update.
    UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
    float deviceOrientationRadians = 0.0f;
    if (orientation == UIDeviceOrientationLandscapeLeft) {
        deviceOrientationRadians = M_PI_2;
    }
    if (orientation == UIDeviceOrientationLandscapeRight) {
        deviceOrientationRadians = -M_PI_2;
    }
    if (orientation == UIDeviceOrientationPortraitUpsideDown) {
        deviceOrientationRadians = M_PI;
    }
    GLKMatrix4 baseRotation = GLKMatrix4MakeRotation(deviceOrientationRadians, 0.0f, 0.0f, 1.0f);

    CMRotationMatrix a = deviceMotion.attitude.rotationMatrix;
    deviceMotionAttitudeMatrix
        = GLKMatrix4Make(a.m11, a.m21, a.m31, 0.0f,
                         a.m12, a.m22, a.m32, 0.0f,
                         a.m13, a.m23, a.m33, 0.0f,
                         0.0f, 0.0f, 0.0f, 1.0f);
    deviceMotionAttitudeMatrix = GLKMatrix4Multiply(baseRotation, deviceMotionAttitudeMatrix);
}
else
{
    // Look straight forward (we're probably in the simulator, or a device without a gyro)
    deviceMotionAttitudeMatrix = GLKMatrix4MakeRotation(-M_PI_2, 1.0f, 0.0f, 0.0f);
}

Answer 2

这里有一些代码来阐明如何使用 Attitude.rotationMatrix

// initial model view matrix
GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -5.f);

// convert CMRotationMatrix to GLKMatrix4
CMRotationMatrix r = motion.attitude.rotationMatrix;
GLKMatrix4 = GLKMatrix4Make(r.m11, r.m21, r.m31, 0.0f,
                            r.m12, r.m22, r.m32, 0.0f,
                            r.m13, r.m23, r.m33, 0.0f,
                             0.0f,  0.0f,  0.0f, 1.0f);

// apply motion rotation matrix
modelViewMatrix = GLKMatrix4Multiply(modelViewMatrix, _motionRotationMatrix);

// apply matrix to effect
self.effect.transform.modelviewMatrix = modelViewMatrix;

Answer 3

我从这个答案中得到了一些提示并提出了一个解决方案：

https://stackoverflow.com/questions/5328848/simulated-an-image-floating-effect-using-coremotion-devicemotion-on-the-iphone/5442962#5442962

if (d != nil) {

    GLKMatrix4 rotMatrix = GLKMatrix4MakeRotation(0, 0, 1, 0);
    float pitch = d.attitude.pitch;

    if (d.gravity.z > 0)
        pitch = -pitch;

    rotMatrix = GLKMatrix4Rotate(rotMatrix, pitch, -1, 0, 0);
    rotMatrix = GLKMatrix4Rotate(rotMatrix, d.attitude.roll, 0, -1, 0);
    rotMatrix = GLKMatrix4Rotate(rotMatrix, d.attitude.yaw, 0, 0, -1);
    rotMatrix = GLKMatrix4Multiply(rotMatrix, GLKMatrix4MakeRotation(M_PI/2, 1, 0, 0));
}

然而，当手机接近垂直时，这种情况就会变得混乱。所以我还在寻找。