Equilateral triangles on surface

Hello, I was wondering what kind of workflow should I undertake to modify my grid of triangles to be more or less equilateral, with gradually changing side lenght

as it is visible on the bottom of the structure I want to create equilateral triangles with 2000~mm lenght while on the top they should gradually decrease. 

How should I approach this problem? I took a lot of time to solve that problems with simple gh solutions but I failed.

for short, what I am looking for is to triangulate given surface into more or less equilateral triangles. Any ideas ?

Thank you in advance :)