How to mimic oddPolygon in Python to check for Self-Intersecting Polygons

aarush

So I want to make a python script that also checks a GDS file for self-intersecting polygons. On the Klayout app, I have a DRC deck that uses the oddPolygon function to check for self-intersections. How can I translate that into Python. Does the API support that as a function? Trying my own sweep-line algorithm seems to give me different results to the KLayout checker. Help would be appreciated!

Edit: It should also find self-intersections (parts where they overlap) in paths like oddPolygon seems to do

Matthias

HI @aarush,

Most DRC functions are basically method calls to "Region", "Edges", "EdgePairs" or "Texts" objects.

In case of "odd_polygon", the method call is "strange_polygon_check" (see here: https://www.klayout.de/doc-qt5/code/class_Region.html#k_293).

To mimic this check, construct a "Region" object with the layer you like to investigate and execute "strange_polygon_check".

Matthias

aarush

So then does something like this work? Or does it iterate over the layers wrong?

    for cell in layout.each_cell():
        for idx in layout.layer_indexes():
            itr    = layout.begin_shapes(cell, idx)
            region = pya.Region(itr)

            region.merged_semantics = False
            strange = region.strange_polygon_check()
            strange.merged_semantics = False

            if not strange.is_empty():
                info  = layout.get_info(idx)
                count = strange.count()
                issues.append(
                    f"In '{cell.name}' (L={info.layer},DT={info.datatype}): "
                    f"{count} self-intersecting piece(s)"
                )

Thank you for all the help,
Aarush

Matthias

No, that is wrong.

A region is already a full layer - you must not iterate over the cells.
You will need to start from a top cell instead.

This should work better:

        cell = layout.top_cell()
        for idx in layout.layer_indexes():
            itr    = layout.begin_shapes(cell, idx)
            region = pya.Region(itr)
...

Matthias

aarush

Thank you Matthias, this is now giving me the same output as the Klayout App!!!!

Best,
Aarush