| DirectX SDK | 
The D3DXMatrixIsIdentity function determines if the given matrix is an identity matrix.
BOOL D3DXMatrixIsIdentity( const D3DXMATRIX* pM );
If the given matrix is an identity matrix, this function returns TRUE; otherwise, this function returns FALSE.
  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.
  Windows CE: Unsupported.
  Version: Requires DirectX 7.0.
  Header: Declared in d3dxmath.h.
  Library: Use d3dx.lib.