D3DXQUATERNION Structure

Describes a quaternion.

Syntax

typedef struct D3DXQUATERNION {
    FLOAT x;
    FLOAT y;
    FLOAT z;
    FLOAT w;
} D3DXQUATERNION;

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 4-D 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, assignment, unary, and binary (including equality) operators.

Structure Information

Header	d3dx9math.h
Minimum operating systems	Windows 98