```
    def draw_lines(self):

        index = 0
        for line_type, end_point in self.path_points:
            # print line_type, end_point
            self.points.InsertNextPoint(end_point[:3])
            self.colors.InsertNextTypedTuple(self.path_colors[line_type])

            line = vtk.vtkLine()
            if index == 0:
                line.GetPointIds().SetId(0, 0)
                line.GetPointIds().SetId(1, 1)
            else:
                line.GetPointIds().SetId(0, index-1)
                line.GetPointIds().SetId(1, index)

            self.lines.InsertNextCell(line)

            index += 1

        # free up memory, lots of it for big files
        self.path_points = []

        self.poly_data.SetPoints(self.points)
        self.poly_data.SetLines(self.lines)

        self.poly_data.GetCellData().SetScalars(self.colors)

        self.data_mapper.SetInputData(self.poly_data)
        self.data_mapper.Update()

        self.path_actor.SetMapper(self.data_mapper)
```