This .Net class wraps AcGeMatrix3d ObjectARX class. 

Class Matrix3d represents an affine transformation of 3D space, including translation. Each matrix M has the form: 

a00 a01 a02 t0
a10 a11 a12 t1
a20 a21 a22 t2
0     0    0    1

where the matrix A: 

a00 a01 a02
a10 a11 a12
a20 a21 a22

is called the linear part of M. 

Column T: 

t0
t1
t2

is called a translational part of M. 

To get Point3d point transformed by corresponding transformation one has to take the product M x P of the matrix M and point-column P = ( pnt.x, pnt.y, pnt.z, 1.0 ) to the power of T . To get Vector3d vector transformed by corresponding transformation one has to take the product M x V of the matrix M and vector-column V = (vec.x, vec.y, vec.z, 0.0) to the power of T. 

Every matrix M is associated with a coordinate system. This coordinate system has the origin (t₀, t₁) and vectors (a₀₀, a₁₀) and (a₀₁, a₁₁) as axes. Matrix M maps the standard coordinate system to the coordinate system with the origin (0, 0, 0) and axes (1, 0, 0), (0, 1, 0), and (0, 0, 1).

Public Structure Matrix3d
Inherits IFormattable
End Structure

public struct Matrix3d : IFormattable {
}