Translucency

Translucency is a concept very closely related to transparency. Blocks, items, entities and other game elements said to be translucent allow for vision to pass through them partially, but not fully.

All translucent blocks use the rendertype_translucent core shader, with the exception of tripwire, which uses rendertype_tripwire.

Blocks that are not translucent, even though they'd be expected to
Water cauldrons, despite containing water, render this water as completely opaque. While it was rendered translucent as expected in prior versions, this seems to be inconsistent and possibly hardware-dependent, and when it fully stopped is currently unknown. Its opacity is also a parity issue, as cauldron water appears translucent as expected $$. This persists to the present day.

Similarly, while tripwire itself is translucent, the region of tripwire which connects to a tripwire hook is not. This causes the region of tripwire attached to the tripwire hook to appear much darker than the rest of it. Mojang have decided to not fix this issue.