Fix and augment documentation.

Specifically, the picture shows four, not three hexahedra being subdivided.

diff --git a/include/deal.II/grid/grid_generator.h b/include/deal.II/grid/grid_generator.h
index 5269a6d0a45d0ec26808c3f00aeb3b81c726300e..18821ddeffbe68cd3992a0e6d17f6b11c2d6bdca 100644 (file)
--- a/include/deal.II/grid/grid_generator.h
+++ b/include/deal.II/grid/grid_generator.h
@@ -2020,14 +2020,16 @@ namespace GridGenerator
    * (quadrilaterals, hexahedra) to a triangulation only consisting of
    * simplices (triangles, tetrahedra).
    *
-   * As an example, the following image shows how a set of three hexahedra
-   * meshing one eighths of a sphere are subdivided into tetrahedra, and how
+   * As an example, the following image shows how a set of four hexahedra
+   * meshing one eighth of a sphere are subdivided into tetrahedra, and how
    * the curved surface is taken into account. Colors indicate how boundary
    * indicators are inherited:
    * @image html "convert_hypercube_to_simplex_mesh_visualization_octant.png"
    *
    * In general, each quadrilateral in 2d is subdivided into eight triangles,
-   * and each hexahedron in 3d into 24 tetrahedra as shown here:
+   * and each hexahedron in 3d into 24 tetrahedra, as shown here (top left
+   * for the 2d case, the rest shows vertex numbers and subdivisions for
+   * a single 3d hexahedron):
    * @image html "convert_hypercube_to_simplex_mesh_visualization.png"
    *
    * Material ID and boundary IDs are inherited upon conversion.