ofMesh triangles index

Hi,

Using ofMesh I’m trying to achieve this look, specifically the blue (fade out to the sides) cut off cone.

Unfortunately this is what I’ve got so far (mind this is only half of it, I was planning to mirror it in some magic way). I can’t seem to figure out how vertex indexing happens at all :frowning:

I’m doing index in this manner - 0:1:2 , 1:2:3, 1:4:3, 4:3:5

And here’s how I’m positioning them:

All help appreciated!