The bug

In 1.15 snapshot 19w38a (judging by the significant size increase in the atlas according to the game's output), the game's textures-atlas started to gain a lot more textures than it had previously. What originally only stored the textures for blocks, items and fluids would gain the textures of chests, beds, banner patterns, shield patterns, shulkers and signs in 19w38a and the following snapshots.

In the first 1.15 pre-release, the textures-atlas saw a major split to remove a lot of these textures as to relegate them to new, dedicated atlases, presumably to reduce its size. Signs got moved to the new signs.png-atlas, chests to chest.png-atlas and so on.

However, despite this, some textures still remain in the blocks and items atlas in current versions that were added in 1.15 and were not removed in the aforementioned split, even though they should have been due to being outwith the scope of said atlas. The following textures are present, all at the top left with the exception of the last two:

• /entities/banner_base.png
• /entities/shield_base.png
• /entities/shield_base_nopattern.png
• /entities/conduit/base.png
• /entities/conduit/cage.png
• /entities/conduit/wind.png
• /entities/conduit/wind_vertical.png
• /entities/enchanting_table_book.png
• /entities/bell/bell_body.png
• /entities/conduit/closed_eye.png
• /entities/conduit/open_eye.png

None of these textures should be present on the atlas - they weren't present before despite the textures still existing in the game, and the reason why they're there is due to being left over from the aforementioned move in 1.15-pre1.

How to reproduce

Note: this reproduction method relies on MC-236285 to display certain parts of the atlas. If said bug is fixed, there may not be a way to reproduce this in vanilla, even if the issue is still present. If fixed, it may be advisable to add a way to intentionally display or export atlases for debugging purposes, for example a /printatlas command.

1. Download and apply the attached resource pack (I will try to attach a version of the resource pack for each release should the atlas change enough to warrant it.) The resource pack only changes one model and so should not interfere with how the atlas is constructed. This and the default resource pack are the only ones that should be applied - others may interfere.
2. Place a lantern on the ground

Resource pack downloads

• 1.17.1 / 21w44a: texture-atlas-section-viewer-1.17.1-v1.0.zip

Expected results

The textures at the top left corner would be flowing water and flowing lava, since these are the largest textures in the textures/block/ directory. (This is what has been the case since 1.6, as could be seen via bugs such as MC-17132, MC-47105, MC-121759 and MC-138797, in which the attempted generation of undefined particles would result in the very top left section of the atlas being used, which is where flowing lava was.)

Actual results

The textures listed in the introduction can be seen at the top left of the atlas, despite seeing no use whatsoever in (non-entity-rendered) block models, item models or fluids.

How to fix

Either these textures could just be removed from atlases entirely, or they could be collectively split off into a new atlas: minecraft:textures/atlas/block_entities.png-atlas (which could possibly gain more textures, such as tridents). The block breaking textures could also be moved there due to not being associated with any models (see also MC-200944).