Question about Adaptation to an input size map

Dear MMG users and developers,
I am exploring MMG. I am following the tutorials (2d Mesh adaptation to a solution).
The .sol file defined a size map there. At each vertex, it associates the desired size of the surrounding elements of the mesh. So my question is, what the size in the .sol file exactly is? Does it mean the average volume ? Or average length of all edges surrounding the vertex? And what is the unit?
Thanks a lot,
Xiaodong

Dear Xiaodong,

Thank you for your interest in MMG. As you said, in the size map, values are defined at vertices. For each vertex, it defines a target length for all edges lying around this vertex. MMG then tries to produce (as much as possible) a mesh where each edge has a length of 1 with respect to the size map.

Please consult this article for more specific details about the definition of the size map (section 4.2).

Concerning the unit, it is arbitrary. It only needs to be consistent with the dimensions of the mesh.

Kind regards,
Corentin