# D3DXQuaternionMultiply Function

Multiplies two quaternions.

Syntax

```D3DXQUATERNION *D3DXQuaternionMultiply(          D3DXQUATERNION *pOut,
CONST D3DXQUATERNION *pQ1,
CONST D3DXQUATERNION *pQ2
);```

Parameters

pOut
[in, out] Pointer to the D3DXQUATERNION structure that is the result of the operation.
pQ1
[in] Pointer to a source D3DXQUATERNION structure.
pQ2
[in] Pointer to a source D3DXQUATERNION structure.

Return Value

Pointer to a D3DXQUATERNION structure that is the product of two quaternions.

Remarks

The result represents the rotation Q1 followed by the rotation Q2 (Out = Q1 * Q2). This is done so that D3DXQuaternionMultiply maintain the same semantics as D3DXMatrixMultiply because unit quaternions can be considered as another way to represent rotation matrices.

Transformations are concatenated in the same order for both the D3DXQuaternionMultiply and D3DXMatrixMultiply functions. For example, assuming mX and mY represent the same rotations as qX and qY, both m and q will represent the same rotations.

```D3DXMatrixMultiply(&m, &mX, &mY);

D3DXQuaternionMultiply(&q, &qX, &qY);```

The multiplication of quaternions is not commutative.

The return value for this function is the same value returned in the pOut parameter. In this way, the D3DXQuaternionMultiply function can be used as a parameter for another function.

Function Information