masque/README.md
2023-10-13 00:50:01 -07:00

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# Masque README
Masque is a Python module for designing lithography masks.
The general idea is to implement something resembling the GDSII file-format, but
with some vectorized element types (eg. circles, not just polygons) and the ability
to output to multiple formats.
- [Source repository](https://mpxd.net/code/jan/masque)
- [PyPI](https://pypi.org/project/masque)
## Installation
Requirements:
* python >= 3.11
* numpy
* klamath (used for GDSII i/o)
Optional requirements:
* `ezdxf` (DXF i/o): ezdxf
* `oasis` (OASIS i/o): fatamorgana
* `svg` (SVG output): svgwrite
* `visualization` (shape plotting): matplotlib
* `text` (`Text` shape): matplotlib, freetype
Install with pip:
```bash
pip install 'masque[oasis,dxf,svg,visualization,text]'
```
## Overview
A layout consists of a hierarchy of `Pattern`s stored in a single `Library`.
Each `Pattern` can contain `Ref`s pointing at other patterns, `Shape`s, and `Label`s.
`masque` departs from several "classic" GDSII paradigms:
- Layer info for `Shape`ss and `Label`s is not stored in the individual shape and label objects.
Instead, the layer is determined by the key for the container dict (e.g. `pattern.shapes[layer]`).
* This simplifies many common tasks: filtering `Shape`s by layer, remapping layers, and checking if
a layer is empty.
* Technically, this allows reusing the same shape or label object across multiple layers. This isn't
part of the standard workflow since a mixture of single-use and multi-use shapes could be confusing.
* This is similar to the approach used in [KLayout](https://www.klayout.de)
- `Ref` target names are also determined in the key of the container dict (e.g. `pattern.refs[target_name]`).
* This similarly simplifies filtering `Ref`s by target name, updating to a new target, and checking
if a given `Pattern` is referenced.
- `Pattern` names are set by their containing `Library` and are not stored in the `Pattern` objects.
* This guarantees that there are no duplicate pattern names within any given `Library`.
* Likewise, enumerating all the names (and all the `Pattern`s) in a `Library` is straightforward.
- Each `Ref`, `Shape`, or `Label` can be repeated multiple times by attaching a `repetition` object to it.
* This is similar to how OASIS reptitions are handled, and provides extra flexibility over the GDSII
approach of only allowing arrays through AREF (`Ref` + `repetition`).
- `Label`s do not have an orientation or presentation
* This is in line with how they are used in practice, and how they are represented in OASIS.
- Non-polygonal `Shape`s are allowed. For example, elliptical arcs are a basic shape type.
* This enables compatibility with OASIS (e.g. circles) and other formats.
* `Shape`s provide a `.to_polygons()` method for GDSII compatibility.
- Most coordinate values are stored as 64-bit floats internally.
* 1 earth radii in nanometers (6e15) is still represented without approximation (53 bit mantissa -> 2^53 > 9e15)
* Operations that would otherwise clip/round on are still represented approximately.
* Memory usage is usually dominated by other Python overhead.
- `Pattern` objects also contain `Port` information, which can be used to "snap" together
multiple sub-components by matching up the requested port offsets and rotations.
* Port rotations are defined as counter-clockwise angles from the +x axis.
* Ports point into the interior of their associated device.
* Port rotations may be `None` in the case of non-oriented ports.
* Ports have a `ptype` string which is compared in order to catch mismatched connections at build time.
* Ports can be exported into/imported from `Label`s stored directly in the layout,
editable from standard tools (e.g. KLayout). A default format is provided.
## Glossary
- `Library`: A collection of named cells. OASIS or GDS "library" or file.
- "tree": Any Library which has only one topcell.
- `Pattern`: A collection of geometry, text labels, and reference to other patterns.
OASIS or GDS "Cell", DXF "Block".
- `Ref`: A reference to another pattern. GDS "AREF/SREF", OASIS "Placement".
- `Shape`: Individual geometric entity. OASIS or GDS "Geometry element", DXF "LWPolyline" or "Polyline".
- `repetition`: Repetition operation. OASIS "repetition".
GDS "AREF" is a `Ref` combined with a `Grid` repetition.
- `Label`: Text label. Not rendered into geometry. OASIS, GDS, DXF "Text".
- `annotation`: Additional metadata. OASIS or GDS "property".
## Syntax, shorthand, and design patterns
Most syntax and behavior should follow normal python conventions.
There are a few exceptions, either meant to catch common mistakes or to provide a shorthand for common operations:
### `Library` objects don't allow overwriting already-existing patterns
```python3
library['mycell'] = pattern0
library['mycell'] = pattern1 # Error! 'mycell' already exists and can't be overwritten
del library['mycell'] # We can explicitly delete it
library['mycell'] = pattern1 # And now it's ok to assign a new value
library.delete('mycell') # This also deletes all refs pointing to 'mycell' by default
```
### Insert a newly-made hierarchical pattern (with children) into a layout
```python3
# Let's say we have a function which returns a new library containing one topcell (and possibly children)
tree = make_tree(...)
# To reference this cell in our layout, we have to add all its children to our `library` first:
top_name = tree.top() # get the name of the topcell
name_mapping = library.add(tree) # add all patterns from `tree`, renaming elgible conflicting patterns
new_name = name_mapping.get(top_name, top_name) # get the new name for the cell (in case it was auto-renamed)
my_pattern.ref(new_name, ...) # instantiate the cell
# This can be accomplished as follows
new_name = library << tree # Add `tree` into `library` and return the top cell's new name
my_pattern.ref(new_name, ...) # instantiate the cell
# In practice, you may do lots of
my_pattern.ref(lib << make_tree(...), ...)
```
We can also use this shorthand to quickly add and reference a single flat (as yet un-named) pattern:
```python3
anonymous_pattern = Pattern(...)
my_pattern.ref(lib << {'_tentative_name': anonymous_pattern}, ...)
```
### Place a hierarchical pattern into a layout, preserving its port info
```python3
# As above, we have a function that makes a new library containing one topcell (and possibly children)
tree = make_tree(...)
# We need to go get its port info to `place()` it into our existing layout,
new_name = library << tree # Add the tree to the library and return its name (see `<<` above)
abstract = library.abstract(tree) # An `Abstract` stores a pattern's name and its ports (but no geometry)
my_pattern.place(abstract, ...)
# With shorthand,
abstract = library <= tree
my_pattern.place(abstract, ...)
# or
my_pattern.place(library << make_tree(...), ...)
### Quickly add geometry, labels, or refs:
The long form for adding elements can be overly verbose:
```python3
my_pattern.shapes[layer].append(Polygon(vertices, ...))
my_pattern.labels[layer] += [Label('my text')]
my_pattern.refs[target_name].append(Ref(offset=..., ...))
```
There is shorthand for the most common elements:
```python3
my_pattern.polygon(layer=layer, vertices=vertices, ...)
my_pattern.rect(layer=layer, xctr=..., xmin=..., ymax=..., ly=...) # rectangle; pick 4 of 6 constraints
my_pattern.rect(layer=layer, ymin=..., ymax=..., xctr=..., lx=...)
my_pattern.path(...)
my_pattern.label(layer, 'my_text')
my_pattern.ref(target_name, offset=..., ...)
```
### Accessing ports
```python3
# Square brackets pull from the underlying `.ports` dict:
assert pattern['input'] is pattern.ports['input']
# And you can use them to read multiple ports at once:
assert pattern[('input', 'output')] == {
'input': pattern.ports['input'],
'output': pattern.ports['output'],
}
# But you shouldn't use them for anything except reading
pattern['input'] = Port(...) # Error!
has_input = ('input' in pattern) # Error!
```
### Building patterns
```python3
library = Library(...)
my_pattern_name, my_pattern = library.mkpat(some_name_generator())
...
def _make_my_subpattern() -> str:
# This function can draw from the outer scope (e.g. `library`) but will not pollute the outer scope
# (e.g. the variable `subpattern` will not be accessible from outside the function; you must load it
# from within `library`).
subpattern_name, subpattern = library.mkpat(...)
subpattern.rect(...)
...
return subpattern_name
my_pattern.ref(_make_my_subpattern(), offset=..., ...)
```
## TODO
* Better interface for polygon operations (e.g. with `pyclipper`)
- de-embedding
- boolean ops
* Tests tests tests
* check renderpather
* pather and renderpather examples