code: public Matrix4d set(Matrix3dc mat) {
          m00 = mat.m00();
          m01 = mat.m01();
          m02 = mat.m02();
          m03 = 0.0;
          m10 = mat.m10();
          m11 = mat.m11();
          m12 = mat.m12();
          m13 = 0.0;
          m20 = mat.m20();
          m21 = mat.m21();
          m22 = mat.m22();
          m23 = 0.0;
          m30 = 0.0;
          m31 = 0.0;
          m32 = 0.0;
          m33 = 1.0;
          properties = PROPERTY_AFFINE;
          return this;
      }
docs: Set the upper left 3x3 submatrix of this {@link Matrix4d} to the given {@link Matrix3dc}
  and the rest to identity.
  
  @see #Matrix4d(Matrix3dc)
  
  @param mat
  the {@link Matrix3dc}
  @return this