Or Avatar Rendering Cost, as they tried to call it, but that’s really what this parameter is.
Technically, ARC is supposed to measure the computational requirements of rendering a specific avatar with a specific attachment combination. But, it does this in abstract parrots — meaning that it’s units do not correspond directly to any computational power measurement I know of — and the abstract parrots fly wherever they damn well please.
When this topic was first discussed at the Forum Cartel hangout in my presence, Ordinal Malaprop demonstrated a ring that would bump the wearer’s ARC by a whopping 4000 — which is the base ARC of my primmiest complete outfit. The ring did not induce any noticeable FPS drop. Now that I have come in possession of a similar object myself — a lovely, very detailed pair of glasses consisting of 252 prims — I had the opportunity to finally track down a measurable FPS drop that can be attributed to the 2500 ARC that they add to my avatar.
It’s about 0.5 FPS. On an Eee PC 701. With it’s puny Intel GMA 900 onboard video card. And Eee PC only notices that difference because it barely renders anything at all, and is a machine woefully underpowered to run Second Life in any fashion, it can only do so with a generous amount of kicking.
Further experiments show that while an avatar wearing no prims has an ARC of 1 regardless of the type of system clothing they have on or absence of such, turning off rendering avatars completely on the Eee results in FPS tripling — 4 FPS to 18! — from when showing just one avatar.
It can be safely said, therefore, that no single avatar’s ARC can significantly affect performance of a specific rendering client, if running on a real computer, because either the avatar’s mesh itself or some accompanying computation are quite computationally intensive even with no prims attached to it. The number of avatars on screen matters far more than the complexity of rendering of every individual outfit.
So in effect ARC does little more than promote people competing who can get it higher, and causes lynch mobs when the lag actually results from poor server performance or excessive numbers of avatars on screen.