Armor Renderer Upgrades

[8s2]

Vanilla's rendering overhaul with the RenderCommandQueue has made it nearly impossible to create a custom armor renderer that can render properly on any biped entity with the ArmorRenderer in its current implementation. In Vanilla, the setAngles method for models is now called when a ModelCommand is rendered, meaning that calling it before submitting a model to the render queue is not a reliable way to transform a model.

For example, the current armor rendering test mod adds a renderer for a helmet and chestplate. The model has visibility of its parts set based on the equipment slot, but because this happens before the model is submitted, it leads to visibility conflicts when the helmet and chestplate are worn at the same time. Furthermore, the model's arms swing when it is worn on an armor stand (ignores the armor stand's poses too) and it does not scale properly on differently sized biped mobs.

I am creating this pull request to not only provide a solution for this issue, but to also provide some related upgrades that help with armor rendering.

This PR includes:

• A factory-based option for registering an ArmorRenderer.
  • Current implementations of ArmorRenderer need a mutable and nullable model field that is checked on render and instantiated if null.
  • Renderers registered with a factory are reinstantiated on resource pack reload, which keeps their models up to date.
• The TransformCopyingModel
  • A workaround for transforms being applied on model command render, this model type has a source (Model<? super S>) and delegate (Model<? super D>) model field, with its render state holding both the source and delegate states at the same time (Pair<S, D>). When the setAngles method for this model is called, it sets the source model's angles using the first pair value, copies the transforms to the delegate model, then optionally sets the angles for the delegate model. The delegate model is what gets rendered.
  • Two static methods for rendering a TransformCopyingModel have been added to ArmorRenderer, based on the renderPart static method that used to be there.
• EntityModelLayerRegistry register method for EquipmentModelData<EntityModelLayer>
  • Vanilla now handles armor models using the EquipmentModelData class, this allows users to do the same.
• FabricModel injected interface
  • Adds the getChildPart and copyTransforms methods, which were needed to make the TransformCopyingModel to function. I find them useful enough to users for this to be a injected interface rather than just a mixin duck.
  • Models now cache a map of their model parts with a String key for their names.

[Sollace]

I wouldn't say it's entirely impossible. For example, I'm making use of a custom render command for my in-progress porting of Mine little Pony to 1.21.10

https://github.com/MineLittlePony/MineLittlePony/blob/1.21.10/src/main/java/com/minelittlepony/client/render/command/CustomModelRenderCommand.java

[modmuss50]

Generally looks great, just a few questions.

[modmuss50]

Looks good to me, but really needs someone familar with this area to approve.

[Juuxel]

Looks generally fine to me.

I have a custom ArmorRenderer in 1.21.10 that doesn't need these changes, but I assume that's because I render block models instead of entity models.