def _assemble_triangles(animal_obj):
    """ Computes a basic triangulation on the regular coordinates of an animal.

    Parameters
    ----------
    animal_obj : Animal() object
        Initialized with regular coordinates set/updated

    Returns
    -------
    list of triples of ints
        Specifying the indices of the vertices for each triangle in the triangulation of
        a surface.
    """
    #store relevant parameters
    num_x_grid, num_y_grid = animal_obj.get_num_grids()

    #initialize triangle list
    triangles = []

    #iterate through lower left corners of grid and append canonical triangles
    for i in range(num_x_grid-1):
        for j in range(num_y_grid-1):
            triangles.append([i*num_y_grid+j, (i+1)*num_y_grid+j, (i+1)*num_y_grid+(j+1)])
            triangles.append([i*num_y_grid+j, (i+1)*num_y_grid+(j+1), i*num_y_grid+(j+1)])

    return triangles