Fine tuning POV-Ray settings for high quality images

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# This script creates pictures of sample structures, the cut sqs cell will keep
# the same crystallographic orientation in the image as the unit cell
from ase import build
from ase.data import covalent_radii
from ase.data.colors import jmol_colors as chemical_colors
from ase.io.pov import get_bondpairs, write_pov

unit_cell = build.bulk('AlN', 'wurtzite', a=3.129, c=5.017)
sqs_cell = build.cut(unit_cell, a=[1, 0, 1], b=[-2, -2, 0], c=[1, -1, -1])
names = ['unit_cell', 'sqs_cell']
list_of_atoms_obj = [unit_cell, sqs_cell]

# The rest are rendering settings
# see the gallery to see examples of the built-in styles
style = 'simple'
# reverts to jmol_colors if not unspecified
color_dict_rgb255 = {'N': [23, 111, 208], 'Ga': [230, 83, 17]}

# used to automatically guess bonds
covalent_radius_bond_cutoff_scale = 0.9

# for the rendering atom radii
radius_dict = {
    'O': 0.8,
    'Al': 0.6,
}
# for unspecified elements
radius_scale = 0.6

# use ASE GUI to find your perfect orientation
# rotation = '45x, -35.264y, 30z' # down <111> for a cubic structure
# rotation = '0x, 0y, 0z' # down z-axis
rotation = '37x, -79y, -128z'

# povray specific kwrds
kwargs = {
    'transparent': True,  # Transparent background
    'canvas_width': None,  # Width of canvas in pixels
    'canvas_height': 720,  # Height of canvas in pixels
    # 'image_height' : 22,
    # 'image_width'  : 102, # I think these are in atomic units
    # 'image_plane'  : None,  # Distance from front atom to image plane
    #                        # (focal depth for perspective)
    # 'camera_dist'  : 170.0,   # Distance from camera to front atom,
    # 'camera_type': 'orthographic angle 35',  # 'perspective angle 20',
    #                                          ultra_wide_angle
    # 'area_light'   : [(2., 3., 40.) ,# location
    #                  'White',       # color
    #                  .7, .7, 3, 3], # width, height, Nlamps_x, Nlamps_y
    # 'point_lights' : [],             # [[loc1, color1], [loc2, color2],...]
    # 'background'   : 'White',        # color
    'depth_cueing': False,
    'celllinewidth': 0.01,  # Radius of the cylinders representing the cell
}

# generic projection settings (passed to plotting variables)
generic_projection_settings = {
    'rotation': rotation,
    'show_unit_cell': 2,
    # 'extra_offset':(2.0, 0.0)
}

# some nice helper functions


def make_radius_list(atoms, radius_dict, radius_scale=0.9):
    per_atom_list = []
    for z, symbol in zip(atoms.get_atomic_numbers(), atoms.symbols):
        if symbol in radius_dict.keys():
            per_atom_list.append(radius_dict[symbol])
        else:
            per_atom_list.append(radius_scale * covalent_radii[z])
    return per_atom_list


def make_color_list(atoms, color_dict):
    per_atom_list = []
    for z, symbol in zip(atoms.get_atomic_numbers(), atoms.symbols):
        if symbol in color_dict.keys():
            per_atom_list.append(color_dict[symbol])
        else:
            per_atom_list.append(chemical_colors[z])
    return per_atom_list


# converting RGB255 to RGB1 for povray.
color_dict = {}
for symbol in color_dict_rgb255:
    color_dict[symbol] = [val / 255.0 for val in color_dict_rgb255[symbol]]

# loop over atoms objects to render them
for atoms, name in zip(list_of_atoms_obj, names):
    radius_list = make_radius_list(
        atoms, radius_dict, radius_scale=radius_scale
    )
    bondpairs = get_bondpairs(atoms, radius=covalent_radius_bond_cutoff_scale)
    color_list = make_color_list(atoms, color_dict)

    # These have to be set per-atom
    kwargs['textures'] = len(atoms) * [style]
    kwargs['colors'] = color_list
    kwargs['bondatoms'] = bondpairs

    # PlottingVariables needs the radii to set the image plane size
    generic_projection_settings['radii'] = radius_list

    pov_name = name + '.pov'
    povobj = write_pov(
        pov_name, atoms, **generic_projection_settings, povray_settings=kwargs
    )
    povobj.render()