Tri Patch creates a flat grid with 72 triangular faces. The face count remains at 72, regardless of its size. The faces become larger to fill the area as you increase the size of the grid.

Create panel, activate
(Geometry). Choose Patch Grids from the drop-downlist, then on the Object Type rollout, click Tri Patch.
Select a Tri Patch.
Modify panel, right-click TriPatch in stack view, and choose Editable Patch.
(Vertex).
select a vertex on the patch object and move the vertex to change the surface topology.
You can animate vertices and vectors with an Editable Patch modifier.