[MCM-1758] Custom geo skins bones do not recognise “non-helmets”

Partner Rank: 1
Partner Team Reporting: Noxcrew
Verification builds: 19.20.72
Regression Builds: Since inception.
Summary: When a player equips a helmet when using a custom geo skin it hides certain “bones”. However, when equipping non-helmet blocks the same does not happen. This can lead to z-fighting and other undesired visual bugs
Impact: Users are subjected to visual issues, like Z-fighting, which appear broken and unintended. This affects all live custom skins
Repro Steps:
Download the [ Batman Skin pack|https://www.minecraft.net/en-us/marketplace/pdp?id=f5e31f4d-2c8e-4b84-808d-05928747d9c7]
Equip the Poison Ivy skin

Open up a vanilla world in creative
Give yourself a chainmail helmet
Observe her hair disappears when it is equipped
Remove and change to a non-helmet block, like mob skulls or pumpkins
Observe the hair does not disappear

Observed Results: The “helmet_armour” bones do not get hidden when a non-helmet block is equipped
Expected Results: The “helmet_armour” bones are hidden when blocks like the pumpkin, or mob skulls, are equipped like they do with helmets
Screenshots / Videos attached: Linked video of Poison ivy and Oaken (from the Frozen Skin pack). Oaken shows the Z-fighting at the back of the head.
https://www.youtube.com/watch?v=q5MuBogGq_s - Poison Ivy
https://www.youtube.com/watch?v=t8QxGwtnuuI - Oaken

Notes:
This affects many custom geo skins on the marketplace. As we get more custom skins and with the introduction of the custom geo skin plugin this bug’s occurrence is likely to increase. It has been something we’ve encountered every time we’ve created custom geo skins.
VSO bugs from a recent pack; 1199034, 1199052, 1201338, 1201389, 1201467

Although Custom geo skins are limited to IP or special products, these tend to be the products which hold the tightest limitations when trying to faithfully represent another IP holder’s characters. Sometimes using inflation or offsetting the head by minimal amounts has knock on effects that cause more problems than fix the tiny use case of the mob skull or pumpkin. To add further issues, the mob skulls, dragon head and pumpkin are all different sizes. Whilst the pivot that controls the height offset for these is different from the helmet.