Rotation

The transformations described here are for left-handed coordinate systems, and so may be different from transformation matrices that you have seen elsewhere. For more information, see 3-D Coordinate Systems.

The following transformation rotates the point (x, y, z) around the x-axis, producing a new point (x', y', z').

In these example matrices, the Greek letter theta (θ) stands for the angle of rotation, in radians. Angles are measured clockwise when looking along the rotation axis toward the origin.

[C++]

In a C++ application, use the D3DUtil_SetRotateXMatrix, D3DUtil_SetRotateYMatrix, and D3DUtil_SetRotateZMatrix helper functions in the D3dutil.cpp file to create rotation matrices. (The D3dutil.cpp file is included with this SDK.) The following is the sample code for the D3DUtil_SetRotateXMatrix helper function.

VOID D3DUtil_SetRotateXMatrix( D3DMATRIX& mat, FLOAT fRads )
{
    D3DUtil_SetIdentityMatrix( mat );
    mat._22 =  cosf( fRads );
    mat._23 =  sinf( fRads );
    mat._32 = -sinf( fRads );
    mat._33 =  cosf( fRads );
}v

[Visual Basic]

Visual Basic applications can use the DirectX7.RotateXMatrix, DirectX7.RotateYMatrix, and DirectX7.RotateZMatrix methods to create rotation matrices.

If you manually created a matrix for rotation about an axis—in this case, the x-axis—the source code would look something like the following:

Sub CreateXRotation(ret As D3DMATRIX, rads As Single)
    Dim cosine As Single
    Dim sine As Single
    cosine = Cos(rads)
    sine = Sin(rads)
    
    Call dx.IdentityMatrix(ret) ' Method of the DirectX7 object.
    
    ret.rc22 = cosine
    ret.rc23 = sine
    ret.rc32 = -sine
    ret.rc33 = cosine
End Sub