Issue:

Item model when using different display rotations that will result in the "same model", as in visually looking exactly the same as the unrotated version of the model, will have inconsistent shading on faces.

For example, the provided resource pack contains a composite item model that stack 16 of the same ring model horizontally, only differing by 22.5 degrees on the X component of the head display rotation. Since they are the same model and rotating only by 22.5 would still result in a model that looks visually the same as the non-rotated version, the model should be shaded the exact same as the non-rotated version. However, currently the models are shaded incorrectly. 

Steps to reproduce:

1. Download and apply the provided resource pack (shading_bug.zip)
2. Run this command to spawn the visualization: 

   /summon item_display ~ ~ ~ {item_display:"head",item:{id:"minecraft:stick",count:1,components:{"minecraft:item_model":"model"}}}

Expectation:

Reality: