Using matlab to generate complex graphics stl file

Hi, I have been able to use matlab to generate cuboid stl files, but the stl files of concave bodies always make mistakes, because there are always problems in the triangle division of concave surface. Could you please tell me how to automatically divide triangles that can generate stl files on concave surface.I would really appreciate it if you could help me.

The generated cuboid stl file

The graph you want to generate