The D3DUtil_SetViewMatrix helper function, from the D3dutil.cpp source file that is included with this SDK, creates a view matrix based on the camera location and a look-at point passed to it. It uses the Magnitude, CrossProduct, and DotProduct D3D_OVERLOADS helper functions.

HRESULT D3DUtil_SetViewMatrix( D3DMATRIX& mat, D3DVECTOR& vFrom, 
       D3DVECTOR& vAt, D3DVECTOR& vWorldUp )
{
    // Get the z basis vector, which points straight ahead. This is the
    // difference from the eyepoint to the lookat point.
    D3DVECTOR vView = vAt - vFrom;
 
    FLOAT fLength = Magnitude( vView );
    if( fLength < 1e-6f )
return E_INVALIDARG;
 
    // Normalize the z basis vector
    vView /= fLength;
 
    // Get the dot product, and calculate the projection of the z basis
    // vector onto the up vector. The projection is the y basis vector.
    FLOAT fDotProduct = DotProduct( vWorldUp, vView );
 
    D3DVECTOR vUp = vWorldUp - fDotProduct * vView;
 
    // If this vector has near-zero length because the input specified a
    // bogus up vector, let's try a default up vector
    if( 1e-6f > ( fLength = Magnitude( vUp ) ) )
    {
vUp = D3DVECTOR( 0.0f, 1.0f, 0.0f ) - vView.y * vView;
 
// If we still have near-zero length, resort to a different axis.
if( 1e-6f > ( fLength = Magnitude( vUp ) ) )
{
    vUp = D3DVECTOR( 0.0f, 0.0f, 1.0f ) - vView.z * vView;
 
    if( 1e-6f > ( fLength = Magnitude( vUp ) ) )
return E_INVALIDARG;
}
    }
 
    // Normalize the y basis vector
    vUp /= fLength;
 
    // The x basis vector is found simply with the cross product of the y
    // and z basis vectors
    D3DVECTOR vRight = CrossProduct( vUp, vView );
    
    // Start building the matrix. The first three rows contains the basis
    // vectors used to rotate the view to point at the lookat point
    D3DUtil_SetIdentityMatrix( mat );
    mat._11 = vRight.x;    mat._12 = vUp.x;    mat._13 = vView.x;
    mat._21 = vRight.y;    mat._22 = vUp.y;    mat._23 = vView.y;
    mat._31 = vRight.z;    mat._32 = vUp.z;    mat._33 = vView.z;
 
    // Do the translation values (rotations are still about the eyepoint)
    mat._41 = - DotProduct( vFrom, vRight );
    mat._42 = - DotProduct( vFrom, vUp );
    mat._43 = - DotProduct( vFrom, vView );
 
    return S_OK;
}

As with the world transformation, you call the IDirect3DDevice7::SetTransform method to set the view transformation, specifying the D3DTRANSFORMSTATE_VIEW flag in the first parameter. See Setting Transformations, for more information.

Visual Basic applications use the DirectX7.ViewMatrix method to create view matrix based on the camera location, a look-at point, an "up" vector (usually 0,1,0), and a roll value specified in radians.

The following example code, written in Visual Basic, shows how the ViewMatrix method can be used.

' For this example, the g_dx variable contains a valid reference 
' to a global DirectX7 object.
Dim matView  As D3DMATRIX
Dim vFrom As D3DVECTOR, _ 
    vTo As D3DVECTOR, _ 
    vUp As D3DVECTOR

    vFrom.x = 0: vFrom.y = 0: vFrom.z = -15
    vTo.x = 0: vTo.y = 0: vTo.z = 0
    vUp.x = 0: vUp.y = 1: vUp.z = 0

' Initialize the matrix to the identity.
g_dx.IdentityMatrix matView

' Create a view matrix with a camera at 0,0,-15, that points at the 
' world-origin, with no rotation around the vFrom->vTo vector.
Call g_dx.ViewMatrix(matView, vFrom, vTo, vUp, 0)

As with the world transformation, you call the Direct3DDevice7.SetTransform method to set the view transformation, specifying the D3DTRANSFORMSTATE_VIEW flag in the first parameter. See Setting Transformations, for more information.