MEEP Block object showing weird structures at the edges for angles greater than 270 degrees

[aa16oaslak]

Hey everyone- I was examining with different angles of MEEP Block object by applying a rotation to the e1,e2 and e3 vectors with an angle along the rotation axis "Z" (i.e., performing an rotation in the XY plane). I used the following approach:

def meep_block(size, 
               center, 
               material,
               angle=0,
               rot_axis='z',
               e1=mp.Vector3(1, 0, 0),
               e2=mp.Vector3(0, 1, 0),
               e3=mp.Vector3(0, 0, 1),
               **kwargs):
    # Check for valid rotation axis
    if rot_axis not in ['x', 'y', 'z']:
        raise ValueError("Invalid rotation axis. Choose from 'x', 'y', or 'z'.")

    # Set the rotation axis
    if rot_axis == 'x':
        axis = mp.Vector3(1, 0, 0)
    elif rot_axis == 'y':
        axis = mp.Vector3(0, 1, 0)
    else:  # Default: z-axis
        axis = mp.Vector3(0, 0, 1)

    # Apply rotation if angle is non-zero
    if angle != 0:
        e1 = e1.rotate(axis, math.radians(angle))
        e2 = e2.rotate(axis, math.radians(angle))
        e3 = e3.rotate(axis, math.radians(angle))

    # Return the block with the given parameters
    return mp.Block(size=size,
                    center=center,
                    material=material,
                    e1=e1,
                    e2=e2,
                    e3=e3,
                    **kwargs)

One weird thing that I noticed is for angle greater than 270 degrees, I am seeing some distortions at the edges of the MEEP block object (see the below image at angle= -300). Any particular reason for that?

Here are the details about the block objects:

block, center = (-2,0,0)
          size (0.5,2,0)
          axes (1,0,0), (0,1,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)
     block, center = (-0.8,0,0)
          size (0.5,2,0)
          axes (0.707107,-0.707107,0), (0.707107,0.707107,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)
     block, center = (0.4,2,0)
          size (0.5,2,0)
          axes (6.12323e-17,-1,0), (1,6.12323e-17,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)
     block, center = (0,-1.5,0)
          size (0.5,2,0)
          axes (-0.707107,-0.707107,0), (0.707107,-0.707107,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)
     block, center = (2,0,0)
          size (0.5,2,0)
          axes (-1,-1.22465e-16,0), (1.22465e-16,-1,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)
     block, center = (0.5,1,0)
          size (0.5,2,0)
          axes (0.5,0.866025,0), (-0.866025,0.5,0), (0,0,1)
          dielectric constant epsilon diagonal = (1.5625,1.5625,1.5625)

[stevengj]

That's weird, seems like a bug?

[aa16oaslak]

Yeah I have used MEEP's plot2D function and it is a bit weird to see this pattern (attaching the code)-- You can check it out!

def meep_block(size, 
               center, 
               material,
               angle=0,
               rot_axis='z',
               e1=mp.Vector3(1, 0, 0),
               e2=mp.Vector3(0, 1, 0),
               e3=mp.Vector3(0, 0, 1),
               **kwargs):
    """
    Returns the block object for the source.

    Parameters
    ----------
    size : mp.Vector3
        Size of the block in the x, y, and z directions.
    center : mp.Vector3
        Center of the block in the x, y, and z directions.
    material : mp.Medium
        Material of the block.
    angle : float (optional)
        Angle by which the block is rotated w.r.t the rot_axis anticlockwise (default: 0).
    rot_axis : str (optional)
        Axis about which the block is rotated (default: 'x').
    e1, e2, e3 : mp.Vector3 (optional)
        Vectors defining the x, y, and z axes of the block (default: standard unit vectors).
    kwargs : dict
        Additional arguments for the meep.Block().
    """
    
    # Check for valid rotation axis
    if rot_axis not in ['x', 'y', 'z']:
        raise ValueError("Invalid rotation axis. Choose from 'x', 'y', or 'z'.")

    # Set the rotation axis
    if rot_axis == 'x':
        axis = mp.Vector3(1, 0, 0)
    elif rot_axis == 'y':
        axis = mp.Vector3(0, 1, 0)
    else:  # Default: z-axis
        axis = mp.Vector3(0, 0, 1)

    # Apply rotation if angle is non-zero
    if angle != 0:
        e1 = e1.rotate(axis, math.radians(angle))
        e2 = e2.rotate(axis, math.radians(angle))
        e3 = e3.rotate(axis, math.radians(angle))

    # Return the block with the given parameters
    return mp.Block(size=size,
                    center=center,
                    material=material,
                    e1=e1,
                    e2=e2,
                    e3=e3,
                    **kwargs)


single_block = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(-2, 0, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=0)


single_block_45 = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(-0.8, 0, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=-45) 

single_block_90 = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(0.4, 2, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=-90)

single_block_135 = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(0, -1.5, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=-135)

single_block_180 = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(2, 0, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=-180)

single_block_300 = meep_block(size=mp.Vector3(0.5,2,0),
                            center=mp.Vector3(0.5, 1, 0),
                            material=arc_plastic,
                            rot_axis='z',
                            angle=-300)

# Store geometry with labels
geometry_with_labels = [
    (single_block, "original_block (angle=0)"),
    (single_block_45, "rotated_block (angle=-45)"),
    (single_block_90, "rotated_block (angle=-90)"),
    (single_block_135, "rotated_block (angle=-135)"),
    (single_block_180, "rotated_block (angle=-180)"),
    (single_block_300, "rotated_block (angle=-300)")
]

cell_size = mp.Vector3(5, 5, 0)
# Create simulation
sim_with_blocks = mp.Simulation(
    cell_size=cell_size,
    geometry=[block for block, label in geometry_with_labels],
    resolution=50
)

# Visualize with custom labels
plt.figure(figsize=(12, 10))
mp.plot2D(sim_with_blocks)

# Add custom annotations
for block, label in geometry_with_labels:
    plt.annotate(label, xy=(block.center.x, block.center.y), 
                xytext=(5, 5), textcoords='offset points',
                bbox=dict(boxstyle='round,pad=0.3', facecolor='yellow', alpha=0.7),
                fontsize=10)

plt.title('Block Geometry with different angles with rotation axis along Z (i.e., on the XY plane)')
plt.show()