Hi Alexander,
Please see:
Test data(input/output/QGIS)
5077-TopoJson -TopoJson.zip (9.3 KB)
If the input is not valid - this is .json extension , please give me valid .json sample for TopoJson
that I will make full…...determines should we stay as it is 3D geometry or trim it to 2D geometry...you explains how you trim from 3D to 2D with this sample, please...