docs: protected void constructE( Point3D_F64 e2 , Point3D_F64 e3 ) {
  		E.zero();
  
  		for( int i = 0; i < 3; i++ ) {
  			for( int j = 0; j < 3; j++ ) {
  				for( int k = 0; k < 3; k++ ) {
  					// which element in the trifocal tensor is being manipulated
  					int row = 9*i + 3*j + k;
  					// which unknowns are being multiplied by
  					int col1 = j*3 + i;
  					int col2 = k*3 + i + 9;
  
  					E.data[row*18 + col1 ] = e3.getIdx(k);
  					E.data[row*18 + col2 ] = -e2.getIdx(j);
  				}
  			}
  		}
  	}