The bug

If minecraft:tripwire is given a custom model via a resource pack, it will render strangely when placed next to adjacent tripwire units and when viewed through other tripwire or other translucent surfaces.

How to reproduce

A resource pack is attached to this issue which makes minecraft:tripwire use the model for purple stained glass. It also replaces the model for blue stained glass with a copy of the purple stained glass model with all cullface options removed for the sake of comparison.

Build a 3x3x3 cube in the air consisting of minecraft:tripwire (via the string item) and view it from different angles. From some angles, it will appear solid, and from others, all of the inner faces will be visible and none are culled. Experiment with gaps between the tripwire units, viewing tripwire through translucent blocks, viewing translucent blocks through tripwire, and so on.

Expected results

The occlusion, face culling and so on would remain somewhat consistent from all angles (i.e. you shouldn't be able to deduce what direction you'd be looking at the 3x3x3 cube at by going off of what faces are visible and which ones are occluded). For example, there could be no culling at all, there could be full culling so that a cube of tripwire looks identical to a cube of purple stained glass from every angle, or there could even be full occlusion such that all tripwire units behind other tripwire units are hidden (like how ice rendered prior to release 1.7).

Actual results

The weird directional stuff described here.