making sources of complex shapes

[yurivict]

I modified the source of the example bent-waveguide.ipynb to have 6 vertices:
bent-waveguide-1.ipynb

Instead of drawing a polygon with 6 vertices it draws a smaller square:

This square is obviously smaller than 2x2 that was specified in the modified example.

Why is the displayed shape smaller than specified in the vertices array, and why doesn't it have 6 vertices?

Thank you.

[stevengj]

vertices is an argument of mp.Prism, not mp.Volume.

[yurivict]

@stevengj

It says here in the description of the class mp.Volume:

Alternatively, you can specify a list of Vector3 vertices using the vertices parameter. The center and size will automatically be computed from this list.

And the constructor of the mp.Volume class code accepts the named 'volume' argument.

[stevengj]

It still doesn't make a polygon, just a box centered at the mean of the vertices. A Volume is always a box aligned with the cartesian axes.

[yurivict]

Ok, but the size of the box doesn't correspond to the coordinates in the 'vertices' array: #2906

[yurivict]

@stevengj
If mp.Volume doesn't make a polygon, and only makes a box, how to create a source that has a polygon as its shape?
The mp.Source class only has the 'volume' argument that can only accept mp.Volume instances.
And how to create a 3D source of a complex shape?
Are there any examples for this?

[stevengj]

To make a source that covers a complicated shape (e.g. a polygon) that cannot easily be composed from Cartesian boxes, you should

1. Define the volume (or center and size) of the source to be a bounding box that encloses the intended source region.
2. Set the amp_func of the source to be a Python function that returns whatever source you want (e.g. a source that is 1 in a polygon and zero outside).

(Alternatively, you can add a large number of source "boxes" that fill your desired shape.)