okay kinda complicated to explain but.. Is there a way to have the display for firstperson_righthand be a different texture than the one thats in the GUI.
So say you're holding an item, could i make it have a different texture/model entirely than the object thats in the gui/hotbar. Please Help!!
I wish this were possible in Vanilla Minecraft but unfortunately, it is not possible.
Display values only alter how the current model looks in different positions, there is no place in the JSON that allows them to ask for a different model.
The only case I can think of in Vanilla Minecraft where you can have the same block/item have 2 completely different models, is actually with items vs blocks. I.E. Block models that have been physically placed in the world vs the same object but which hasn't been placed yet; in item form (gui, dropped, on-person, etc).
They have separate model files for the same item. "assets/minecraft/models/block/..." & "assets/minecraft/models/item/...". Normally the item model just points to the block model so that they are the same, then maybe changes a few display values. Though this doesn't exactly help your question, I just thought it was good to know.
You actually can if you want two models on the same model. Have the item show in your hotbar, then have a model far below it off your screen and then make it so when you hold it, it is the bottom one. The only problem with that is if you look up there will be a floating model in the air above you. (This requires tinkering with positioning.)
Building off that previous reply, you can additionally make the model for the GUI really small, so it is almost invisible. Then for the hotbar view you can increase the model's scale to show it. Then, when the item is in hand, it will be hard or impossible to see the part of the model used for the hotbar.