Polymesh

Polymesh

Polymesh is a Forge/NeoForge 1.20.1 client runtime for rendering glTF 2.0 models from mod resources.

• Developer guide: docs/POLYMESH_PROJECT.md
• Releases: https://github.com/phe6/polymesh/releases
• Issues: https://github.com/phe6/polymesh/issues

Packaging

• Runtime library jar: polymesh-1.0.0-forge.jar
• Demo/test jar: the_utah_teapot-1.0.0-forge.jar
• CesiumMan proof jar: cesium_man_demo-1.0.0-forge.jar
• glTF assets are discovered under assets/<modid>/models/gltf/*.gltf and *.glb.

Item Registration

Register the item normally, then register its glTF model during client setup:

PolymeshApi.registerItemRenderer(item, new ResourceLocation("mymod", "model_name"),
    GltfRenderOptions.builder()
        .scale(1.0f)
        .animationClip("Walk")
        .loopAnimation(true)
        .build());

The item still needs a custom renderer from initializeClient; return new GltfItemRenderer(theItem) there — it reads the model id and options registered above, so they live in exactly one place.

Runtime Notes

• Static non-skinned meshes are uploaded once to shared GPU buffers and reused by item instances.
• Skinned or morph-target item meshes use persistent VAO/VBO/EBO objects with dynamic vertex-buffer refreshes keyed by animation pose version. This avoids per-frame VertexConsumer triangle emission and only recomputes deformed vertices when animation, skinning, or morph pose changes.
• Normals from glTF are preserved. Missing normals are generated once at load time.
• Tangents from glTF are preserved. Missing tangents are generated when UVs are available for runtime data consumers.
• Embedded .glb images are registered as dynamic Minecraft textures during model load.
• Resource reload clears GPU buffers and rebuilds loaded models.
• Item, entity, and block-entity renderers all share the same render backend (PolymeshRenderer), which prefers the GPU static/animated paths and falls back to the CPU vertex-consumer path when needed (e.g. under an active shader pack).
• glTF extras, extension lists, node names, morph target names, and posed node transforms are kept available for game logic.

Supported Features

• glTF 2.0 .gltf with relative buffers/images
• binary .glb
• node hierarchy and TRS/matrix transforms
• materials with base color texture/factor and alpha modes
• skins, inverse bind matrices, morph targets, and animation channels for item rendering
• runtime node/bone lookup for attachment points, hitbox drivers, and gameplay code
• named morph target lookup and runtime morph weight overrides
• glTF extras metadata on models, nodes, and materials

Demo Mods

• teapot contains the static Utah Teapot item plus a CesiumMan item.
• cesium-man is a minimal proof mod with only one animated cesium_man item backed by assets/cesium_man_demo/models/gltf/cesium_man.glb.

Shader Notes

Polymesh preserves the normals authored in the glTF asset and renders through vanilla-style entity render states. It does not claim shader-pack-side smooth-normal fixes; shader packs that derive lighting from their own geometry pipeline may still need shader-side support.

License

Polymesh — a glTF 2.0 model rendering library for Minecraft Forge/NeoForge 1.20.1 Copyright (C) 2026 Phe

This library is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library (see LICENSE.LESSER and LICENSE). If not, see https://www.gnu.org/licenses/.

Bundled dependencies: jgltf (MIT) and Jackson (Apache-2.0) are repackaged inside the forge jar under their own licenses.