Hello,

I've lantern item which when held will use Cutom Renderer (model).

What I want is when player is holding this item his hand will be lifted.

You know - when you are holding a lantern you usually lift it up, not swing it arount

How can I do that? Maybe using Player API? (have this one implemented).

You can use RenderPlayerEvent.Post and change bipedRightArm.rotateAngle if player is holding your item.

main model is a private variable and so you cannot use it from a RenderPlayerEvent perspective

Well I could just add if statement for my item to ModelBiped class because it wont cause incompatibility (it will also work with other ModelBiped entities like zombies) but this idea is just wrong for Forge coding.

So any other ideas? I need to know how to tell ModelBiped to start rendering stuff different way.

honestly i had that same problem (i wanted to render thing on steve left arm) so i made a coremod giving me the required tools

Why not using reflection ? 

You have the renderplayer instance, you can access modelBipedMain field ?

less lines of code ...

and i had to do like 1000 000 vanilla change anyway, so might as well

Forge provides reflection helper classes, if you are afraid of lines.

Sure you can do with a coremod, but it is clearly not needed in this case.

im not afraid of lines but i have a coremod anyway to do things that are not possible via reflection so might as well