# Obtuse angle in triangulation

Hi!

I’m solving 2D exterior problem. And in my triangulation there are some triangles with angles>pi/2. How can I generate the triangulation only with acute angles. Below is my code on C++.

Thank you.
Ng_Meshing_Parameters mp;
mp.maxh = 0.5;
mp.fineness = 1;
mp.second_order = 0;
Ng_Geometry_2D * geom;
Ng_Init();
Ng_GenerateMesh_2D (geom, &m_tria_mesh.m_pNg_mesh, &mp);
Ng_SaveMesh(m_tria_mesh.m_pNg_mesh, volFileName);

Hi Alex,

there is no guarantee that interior angles are acute. For people working with finite elements it is usually not important.

If you need it: You can hack into the mesh optimizer, and penalize non-acute triangles. Starting point is CalcTriangleBadness (and its gradient below):

Joachim

thanks a lot. I will try penalize non-acute triangles.

I’m a beginner in finite elements. The term Laplace(U) transferes to integration of normal derivative of U by the triangle curve. I use Dirichlet Cell as a poligon of circlepoints(of the inscribed circle) of triangles around. If triangulation consists of non-acute triangles, the poligon is not convex and i dont know how what to do with it. May be some other algorithms for calculating Laplace(U) on triangels.

Thank you