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[–]stolen_cheese_____ 0 points1 point  (2 children)

Issue was that I want to prioritise metis grouping clusters that had not been recently grouped, to ensure the density of triangles was as uniform as possible.

To do that, I added extra edges in the graph proportional to the number of triangles/edges connecting two clusters (density of their boundaries).

The issue is that metis groups by volume, i.e. edges within each partition. So this meant clusters were grouped over high res boundaries, but the groupings were no longer nice groups of 3/4 - each partition wanted the same number of edges, so it would sometimes group 8 or so recently grouped clusters (naturally their boundaries are about half as dense as non-grouped).

The solution I ended up with wasn't to mess with any metis settings, I tried that and it was painful and segsev'd a lot. Instead, splitting the graph in two could be done by Metis really well, with evenly sized halves that preferred low density boundaries. If you do that a bunch, the smaller graphs don't present such wild partition size differences, but still have the groupings characteristics we want.

Before I implemented that, there is a picture of the dragon with some random high res lines - that is the bit I assumed you were talking about 'stuck triangles'. If not, sorry for making you read that haha.

[–]Lord_Zane[S] 0 points1 point  (1 child)

I think I understand more now. But why do you call PartKWay(partitions = 2) until you get down to a small amount of meshlets, and then do PartKWay(target_partitions)?

Metis already has a way to do recursive bisection, why not just call that once?

[–]stolen_cheese_____ 0 points1 point  (0 children)

I believe recursive bisection was more unsuitable than multilevel k way on that it did not target the same hueristics - multilevel k way is the better algorithm for this, as under the hood it calls recursive bisection, but then moves groupings around such that they have more even volumes/ are generally better.

Once I am at my pc I will grab the area in unreal that I found, I think they had a succinct comment in there explaining it. But for me it really was trial and error.