Knowing origin of Polygon

[gsohler]

I'd like to use Clipper2 with more attributes.

Lets say I have am performing an difference of 2 polygon sets like

Result = A - B

A shall exist of 4 rectangles labelled next to each other, labelled from 1-4 and B shall cut all of them into 2 pieces so the Result
contains 8 Rectangles.

Is it possible to determine from the resulting 8 rectangles which original shape(1-4) are they coming from ?

Alternative is to do 4 differences, (but is that as effective as doing 1 difference) ???

thank you for the answers

[philstopford]

Use the Z callback. Assign values to the Z coordinates for the points on each input polygon according to their sequence order (e.g. 0 for 1st, 1 for 2nd polygon, etc...). Run the boolean and query the points. You'll get Z values on those points carried over from the original polygons in the solution. You can also use the callback to set the Z order to -1 for intersection points (i.e. those created in order to generate the solution).

You may need to build Clipper from source for this. I think the release builds (e.g. on nuget and elsewhere) do not have this USEZ preprocessor flag set, so there is no Z coordinate support.