D3DXQUATERNION

Describes a quaternion.

typedef struct D3DXQUATERNION {
    FLOAT x;
    FLOAT y;
    FLOAT z;
    FLOAT w;
} D3DXQUATERNION, *LPD3DXQUATERNION;

Members

x

The x-component.

y

The y-component.

z

The z-component.

w

The w-component.

Remarks

Quaternions add a fourth element to the [ x, y, z] values that define a vector, resulting in arbitrary 4D vectors. However, the following illustrates how each element of a unit quaternion relates to an axis-angle rotation (where q represents a unit quaternion (x, y, z, w), axis is normalized, and theta is the desired CCW rotation about the axis):

q.x = sin(theta/2) * axis.x
q.y = sin(theta/2) * axis.y
q.z = sin(theta/2) * axis.z
q.w = cos(theta/2)

C++ programmers can take advantage of operator overloading and type casting with the D3DXQUATERNION Extensions, which implement overloaded constructors and assignment, unary, and binary (including equality) operators.

See Also

Vectors, Vertices, and Quaternions