>Each chair can be rotated 45 degrees. Each chair is actually a wheat seeds item in an invisible item frame which put on an invisible barrier block. So if you use some plugin to sit on blocks (for example GSit), you can sit on a chair.
If you use EssentialX plugin, this command returns error Error: Unknown item name: .... EssentialX changes the syntax of /give, so you need to use /minecraft:give. See this Issue.
Or you can convert the nearest visible item frame into invisible one:
command
data modify entity @e[type=item_frame, nbt={Invisible:0b}, limit=1, sort=nearest] Invisible set value 1b
To fix the nearest item frame (so it doesn't break even the base block removed or new block placed on it)
command
data modify entity @e[type=item_frame, nbt={Fixed:0b}, limit=1, sort=nearest] Fixed set value 1b
To get invisible barrier block:
command
give @p barrier
Hints for those who create models
Model can be 6×6×6 size.
In the minecraft, you can make 3×3×3 model. You can set scale ×4 for displaying the model in the item frame. Model in item frame is shrinked ×0.5 by Minecraft vanilla behavior.
This is 3×2×1 size table:
This is 5×3×1 size table:
The 5×3×1 size table is not a good solution. If the actual item frame go out of sight, the table disapper. Those large model is only good if player do not get near.
Rotation
The model in the minecraft has a restriction that the cuboid can rotate along only one of three axis. Because you can rotate a model in item frame, you can make a model which looks breaking the restriction.
This resource pack includes X types, 16 colors Xs. Each X can be rotated 45 degrees.
This pack uses the Wheat Seeds System. Each X is actually a wheat seeds item in an invisible item frame which put on an invisible barrier block.
So if you use some plugin to sit on blocks (for example GSit), you can sit on a X.
GSit: https://www.spigotmc.org/resources/gsit-modern-sit-seat-and-chair-lay-and-crawl-plugin-1-13-x-1-17-x.62325/
For the wheat seeds system, see this guide: https://scrapbox.io/nishio/WheatSeedsSystem
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