I am perplexed as to why the Setback operation behaves differently in these two instances. Can anyone shed any light? My desired result is the one on the left.

Here's the rule that I am applying to the initial shape:

Lot-->

setback(2) {0:Yard | remainder:Building}

Yard -->

color("#7FA18A")

Building -->

extrude(*12*)

Please help.

Thanks! Geoff.

I think it is to do with the angle between the edge you are setting back and the adjacent sloping edge.

i.e. if the angle is closer to being a straight edge than a right angle you get the behaviour on the right-hand building, but if it's closer to being a right angle it behaves like the left-hand building.