I noticed something unusual (pardon the pun) after I added a violet killstreak sheen to my Totally Boned Scotsman’s Skullcutter.

And before we continue, I shamelessly admit this is one of the most minor observations I’ve probably ever made in TF2. It’s not quite on the level of 500 characters on the wind you can only notice during a single taunt, but it would fit comfortably into that list of nitpick articles in the final paragraph. Anyway, after a couple different times visiting my Demoman loadout page, I realized the Skullcutter’s inventory icon was occasionally showcasing the purple sheen. It’d happen maybe 10% of the time I opened the page.

Most of the time I viewed my loadout, the icon looked like this…
…but every so often it has the purple glow. And the glowy parts are different each time!

If you have your own specialized killstreak decorated weapon (or want to buy one for a dollar), you can test it for yourself. I checked my other specialized killstreak weapon (a strange festive Ubersaw) and its thumbnail didn’t demonstrate this property, which makes me think this only happens to Decorated weapons. But why?

On first thought, I recognize the necessity for Decorated weapons to have some sort of mechanic for the game to generate a unique inventory icon for each and every weapon. Every other form of customization in Team Fortress 2 does not create a visually one-of-a-kind weapon, even things like Christmas lights and name tags and item qualities. In contrast, every Decorated weapon has its own wear-and-tear, ranging from battle scars to bloodstains and unusual effects.  This would necessitate that Valve finds some way to generate custom inventory icons, in case the player owned multiples of the same Decorated weapon and needed to be able to tell them apart.

In-game inventory icons show the actual appearance of the weapon, while online backpack/market icons use a generic universal thumbnail.

But on second thought, they don’t bother to do this with the Steam Community Market or anywhere online that showcases Decorated weapons. I can only think of two reasons they might have treated the in-game icons differently: (a) It might save memory to generate a temporary thumbnail every time the player visits their inventory as opposed to storing a permament thumbnail in the files somewhere, and (b) I still think Valve is/was planning on adding stickers at some point, and dynamic thumbnails would be a lot more important if the players gained another way to customize their Decorated weapons.

On the other hand, CS:GO weapon stickers don’t appear on in-game inventory icons, so it’s probably the former reason.

But even if we can justify why Valve generates realtime custom thumbnails for Decorated weapons, why are killstreak sheens occasionally appearing on them? Are weapons constantly pre-loaded in the background, the killstreak weapons dutifully glowing every few seconds even though there’s no way for the player to see it? It’s the only explanation I can think of. But to test it, I made some assumptions and did some science:

  • Given: Without any kills, a specialized killstreak weapon pulses its sheen every 7 seconds (Watch the above video on my Skullcutter if you want to time it yourself).
  • Given: The game loads your weapons at the moment you can view your loadout (have you noticed if you immediately visit your inventory after starting up the game, it won’t let you view them for a few seconds?)
  • Given: After I get an inventory icon with a sheen, if I wait exactly 7 seconds before opening the Demoman loadout page again, I can semi-regularly obtain new thumbnails with the sheen appearing somewhere on the weapon.
  • Hypothesis: If I open TF2 and click my Demoman loadout exactly 7 seconds after the game lets me access my inventory, I should regularly be able to view inventory icons with sheens.

So that’s what I did. I repeatedly turned the game off and on, waited 7 seconds to open my Demoman loadout (using my phone as a timer) and…

…it worked! I certainly didn’t have a 100% success rate, but it was happening far more frequently than when I was clicking at random. The fact that the sheen took about a half-second to finish traveling up the weapon gave me a pretty healthy margin for error. What I can’t answer is why Valve has weapons setup like this, to always exist in the background even when the player is sitting on the static menu. It must be easier on the processor to load the weapons once on startup as opposed to everytime they’re somewhere the player can actually see.

By complete accident, I can also confirm the weapon sheens appear on killfeeds, though the sheen on the icon is a little behind the one in the world model.

Aaand, that’s my best guess on why weapon sheens occasionally popup on inventory icons for Decorated weapons. I spent way too long on this, but I hope your curiosity has likewise been sated. If you have any ideas or considerations I didn’t think of, feel free to comment because I’m not a programmer and there are definitely more-qualified TF2 fans out there to deduce what’s going on with these procedural thumbnails.