Max. vertices

jtreu

Hello,
I started this week to create my mask and just noticed the limit (under GDS2 Writer Options):
Max.vertices 8000 (absolute limit 8191).

What exactly does this mean / what are the effects for me? My Mask already has more than 50.000 structures, do I run in problems due to this limit?

Couldn't find something to this topic, so I try my luck here.

Best regards

Julian

Matthias

Hi Julian,

This limit applies to single polygons only. The number of polygons itself is virtually unlimited. So you need really huge polygons to hit this limitation.

There is one practical case where it is pretty easy to create huge polygons: if you invert a layer (subtract a huge number of shapes from some background shape), a large polygon will be created because GDS lacks the capability to represent the holes. Instead these have to be created by cutting into the polygon and wrapping inner contours around the holes.

Some old specifications limit the number of per-polygon vertices to 200, some others to 4000. Depending in the tool you use to process the GDS, you may need to specify a lower limit. If a polygon is encountered with a larger number of vertices, it will be cut into parts until the parts meet the vertex count constraint. This basically means that you can decompose polygons into small pieces if you choose a limit of 4 points for example, although that's not the primary intention of that function :-)

In general, the cutting of polygons can lead to small deviations from the original because of rounding errors. This should be considered if strict pattern fidelity is required.

KLayout also supports a non-standard GDS extension which uses multiple XY records to represent a virtually unlimited number of vertices per polygon. Using this option avoids the cutting of polygons mentioned above but may leave the GDS file incompatible with other tools not supporting the multi-XY extension.

Best regards,

Matthias

jtreu

Great, thanks!