I want to know if there is a way to create a symbol of triangle like $\Delta$ (which I use to mean a bounded triangle) but each edge goes slightly father across the vertex (rather than stop at the vertex as usual).
Using this I was to mean a 2D plane sitting in the 3D space like the one defined by the equation $x+y+z=1$, hence not bounded triangle (so I want a symbol different from $\Delta$ ). Consider various dimension, they will form a cosimplicial affine space.