C OpenGL Quaternion for Camera翻转它

2023年10月12日 173次阅读

当我向右移动目标并向上看它直到它走到-zaxis的180度并决定走向另一个方向时,它会看到目标.

Matrix4x4 camera::GetViewMat()
{
    Matrix4x4 oRotate, oView;
    oView.SetIdentity();

    Vector3 lookAtDir = m_targetPosition - m_camPosition;
    Vector3 lookAtHorizontal = Vector3(lookAtDir.GetX(), 0.0f, lookAtDir.GetZ());
    lookAtHorizontal.Normalize();

    float angle = acosf(Vector3(0.0f, 0.0f, -1.0f).Dot(lookAtHorizontal));
    Quaternions horizontalOrient(angle, Vector3(0.0f, 1.0f, 0.0f));

    ori = horizontalOrient;
    ori.Conjugate();
    oRotate = ori.ToMatrix();

    Vector3 inverseTranslate = Vector3(-m_camPosition.GetX(), -m_camPosition.GetY(), -m_camPosition.GetZ());
    oRotate.Transform(inverseTranslate);

    oRotate.Set(0, 3, inverseTranslate.GetX());
    oRotate.Set(1, 3, inverseTranslate.GetY());
    oRotate.Set(2, 3, inverseTranslate.GetZ());
    oView = oRotate;

    return oView;
}

最佳答案 正如所承诺的那样,一些代码显示了我让摄像机始终在空间中的特定点观察的方式.

首先,我们需要一种从角度和轴构造四元数的方法,我碰巧在pastebin上有这个,角度输入是弧度：

http://pastebin.com/vLcx4Qqh

确保你没有输入轴(0,0,0),这没有任何意义.

现在是实际的更新方法,我们需要让四元数从默认方向旋转相机指向目标点.请注意我刚刚写了这篇文章,它可能需要一些调试,可能需要一些优化,但这至少应该给你一个正确的方向.

void camera::update()
{
    // First get the direction from the camera's position to the target point
    vec3 lookAtDir = m_targetPoint - m_position;

    // I'm going to divide the vector into two 'components', the Y axis rotation
    // and the Up/Down rotation, like a regular camera would work.

    // First to calculate the rotation around the Y axis, so we zero out the y
    // component:
    vec3 lookAtHorizontal = vec3(lookAtDir.x, 0.0f, lookAtDir.z).normalize();

    // Get the quaternion from 'default' direction to the horizontal direction
    // In this case, 'default' direction is along the -z axis, like most OpenGL
    // programs. Make sure the projection matrix works according to this.
    float angle = acos(vec3(0.0f, 0.0f, -1.0f).dot(lookAtHorizontal));
    quaternion horizontalOrient(angle, vec3(0.0f, 1.0f, 0.0f));

    // Since we already stripped the Y component, we can simply get the up/down
    // rotation from it as well.
    angle = acos(lookAtDir.normalize().dot(lookAtHorizontal));
    if(angle) horizontalOrient *= quaternion(angle, lookAtDir.cross(lookAtHorizontal));

    // ...
    m_orientation = horizontalOrient;
}

现在实际上采用m_orientation和m_position来获取世界 – >相机矩阵

// First inverse each element (-position and inverse the quaternion),
// the position is rotated since the position within a matrix is 'added' last
// to the output vector, so it needs to account for rotation of the space.
mat3 rotationMatrix = m_orientation.inverse().toMatrix();
vec3 inverseTranslate = rotationMatrix * -m_position; // Note the minus

mat4 matrix = mat3; // just means the matrix is expanded, the last entry (bottom right of the matrix) is a 1.0f like an identity matrix would be.

// This bit is row-major in my case, you just need to set the translation of the matrix.
matrix[3] = inverseTranslate.x;
matrix[7] = inverseTranslate.y;
matrix[11] = inverseTranslate.z;

编辑我认为它应该是显而易见的,但只是为了完整性,.dot()采用向量的点积,.cross()采用叉积,执行方法的对象是向量A,方法的参数是向量B.

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