2-level neighbors

[NeXTs]

Hello

What's the most efficient way to find n-level neighbors?

I need to find find neighbors up to 4 levels.

There's a center, there are 4 level of neighbors, the further the neighbors the more their transparency.

1 level neighbors implemented by default.
What's the best way to find 2-4 level neighbors?

[arscan]

I'm not sure what is 'best', as it depends on your situation. Perhaps a breadth first traversal that follows neighbors and tracks of how far each node is away from the origin and stops after a distance of n, taking care to not retraverse nodes that have already been visited. If you are changing the origin node frequently, the distance is big, and are rendering using GPU, then you could determine transparency using a simple distance function to the origin node in the vertex shader, but that would redo the (cheap) calculation on every render.