This simple code is working fine:
x =.; y =.; z =.;
syst = {Abs[x - y] <= 1, Abs[y - z] <= 1, Abs[z - x] <= 1};
RegionPlot3D[Apply[And, syst], {x, -2, 2}, {y, -2, 2}, {z, -2, 2}]
Result is like this:
I want to draw a crosssection of this volume with the plane z==0.
In my opinion, the RegionFunction is a good way, but
RegionPlot3D[Apply[And,syst],{x,-2,2},{y,-2,2},{z,-2,2},RegionFunction->Function[{x,y,z},z==0]]
returns
RegionPlot3D::optx: "Unknown option RegionFunction->Function[{x,y,z},z==0] in RegionPlot3D[And@@syst,{x,-2,2},{y,-2,2},{z,-2,2},RegionFunction->Function[{x,y,z},z==0]]."
It seems, that RegionFunction is not allowed in RegionPlot3D. But in the help for RegionPlot3D is written
The arguments supplied to functions in MeshFunctions and RegionFunction are x, y, and z. Please, where is the problem?
Thanks!
