Hi, i'm experimenting with generating buildings via voronoi fracturing. I have a nice collection of buildings and added a mountain node to add some height variation as you might get in a city. However this has meant that the roofs of my buildings are now sloped and i'm stuck on how to make them flat. Could anyone advise please? I'm a big noob when it comes to vex so a step by step would be very handy please if that is a solution offered. Thanks.

One way to do it is to use the Primitive Properties SOP. Set your top prims as the Source Group, enable Do Transformation and then set the Y scale to 0. If you don't already have a group for your top faces you can use the Group SOP to create one (Keep by Normals, Y direction, low Spread Angle).

Or you could use clip and polycap nodes.

You could, however that will leave all your roofs at the same height. Primitive Properties will use each prim's centroid to do the scaling.

The primitive properties SOP was exactly what I was after, thanks guys!