anchor.diff:    Matrix4.zero() : _m4storage = Float32List(16);
   
     /// Identity matrix.
  -  factory Matrix4.identity() => Matrix4.zero()..setIdentity();
  +  Matrix4.identity() : _m4storage = Float32List(16) {
  +    _m4storage[15] = 1.0;
  +    _m4storage[0] = 1.0;
  +    _m4storage[5] = 1.0;
  +    _m4storage[10] = 1.0;
  +  }
   
     /// Copies values from [other].
     factory Matrix4.copy(Matrix4 other) => Matrix4.zero()..setFrom(other);
  
positive.code: 
    /// Returns the determinant of this matrix.
    double determinant() {
      final double det2_01_01 =
          _m4storage[0] * _m4storage[5] - _m4storage[1] * _m4storage[4];
      final double det2_01_02 =
          _m4storage[0] * _m4storage[6] - _m4storage[2] * _m4storage[4];
      final double det2_01_03 =
          _m4storage[0] * _m4storage[7] - _m4storage[3] * _m4storage[4];
      final double det2_01_12 =
          _m4storage[1] * _m4storage[6] - _m4storage[2] * _m4storage[5];
      final double det2_01_13 =
          _m4storage[1] * _m4storage[7] - _m4storage[3] * _m4storage[5];
      final double det2_01_23 =
          _m4storage[2] * _m4storage[7] - _m4storage[3] * _m4storage[6];
      final double det3_201_012 = _m4storage[8] * det2_01_12 -
          _m4storage[9] * det2_01_02 +
          _m4storage[10] * det2_01_01;
      final double det3_201_013 = _m4storage[8] * det2_01_13 -
          _m4storage[9] * det2_01_03 +
          _m4storage[11] * det2_01_01;
      final double det3_201_023 = _m4storage[8] * det2_01_23 -
          _m4storage[10] * det2_01_03 +
          _m4storage[11] * det2_01_02;
      final double det3_201_123 = _m4storage[9] * det2_01_23 -
          _m4storage[10] * det2_01_13 +
          _m4storage[11] * det2_01_12;
      return -det3_201_123 * _m4storage[12] +
          det3_201_023 * _m4storage[13] -
          det3_201_013 * _m4storage[14] +
          det3_201_012 * _m4storage[15];
    }
  
    /// Returns a new vector or matrix by multiplying [this] with [arg].
  
negative.code:     _m4storage[12] *= sw;
      _m4storage[13] *= sw;
      _m4storage[14] *= sw;
    }
  
    /// Create a copy of [this] scaled by a [Vector3], [Vector4] or [x],[y], and
  