The Triangulate modifier converts all faces in a mesh (quads and polygons) to triangular faces. It fulfills the exact same function as the Triangulate tool in Edit Mode.
- Quad Method
Split the quads in nice triangles, slower method.
Split the quads on their 1st and 3rd vertices.
- Fixed Alternate
Split the quads on their 2nd and 4th vertices.
- Shortest Diagonal
Split the quads based on the diagonal distance between their vertices.
- Polygon Method
Arrange the new triangles nicely, slower method.
Split the polygons using an ear-clipping algorithm (gives similar results to the tessellation used for the viewport rendering).
- Minimum Vertices
- Keep Normals
When using custom normals, try to preserve the same shading as before triangulation.