Blockstate "y" rotations turned the geometry counter-clockwise while the
faces were re-assigned clockwise (vanilla). Every east/west variant of an
asymmetric block ended up mirrored on the wrong side of its cell: shelf
mushrooms and ladders floated away from their support, stairs faced
backwards. Rotate clockwise like vanilla, adjust element-rotation axes,
and turn up/down face textures with the model unless uvlock is set.
Edge-case test plugin: shelf mushroom (side + top view) and rotated-block
scenes.
MineTec
a99acad80c