Bevy OpenVAT

Bevy OpenVAT is a high-performance Vertex Animation Texture (VAT) plugin for the Bevy game engine. It enables rendering massive amounts of animated meshes with minimal CPU overhead by offloading animation processing to the vertex shader.

Features

• GPU-Powered Animation: Decodes position and normal offsets directly in the vertex shader for maximum efficiency.
• High Performance Instancing: Uses StorageBuffers to render thousands of animated entities with few draw calls.
• Smooth Interpolation: Supports frame blending for fluid animation playback.
• PBR Compatible: Built on top of Bevy's StandardMaterial, fully supporting lighting, shadows, and depth pre-pass.
• Flexible Control: Per-entity control over playback speed, looping, and time offsets.

Installation

Bevy Version	Crate Version
0.18	0.18

Add the following to your Cargo.toml:

[dependencies]
bevy = "0.18"
bevy_open_vat = "0.18.0"

Asset Preparation

To use this plugin, you need exported VAT assets. Typically, this includes:

1. Geometry (.glb or .gltf): A static mesh with UV2 coordinates mapped for VAT lookup.
2. VAT Texture (.exr): High-precision texture encoding vertex position (and optionally normal) offsets.
3. Remap Info (.json): Metadata containing animation frame counts, bounding box info, and clip names.

Note: Ensure your VAT textures are exported with settings compatible with your shader (e.g., coordinate system handling).

Preparation

1. Install the OpenVAT plugin for Blender.

Conversion Workflow

1. Load Model: Open Blender and load the model file containing your animations.
2. NLA Setup: In the NLA (Non-Linear Animation) editor, combine the animations you want to extract into a single continuous sequence.
3. Open Panel: Open the OpenVAT panel (Press N).
4. Configure: Select the target model and configuration options.

   Important: You must manually set the frame range at the bottom of the panel to match your NLA sequence.

5. Export: 1. Generate/Export the VAT texture using the plugin. 2. Select the preview model generated by OpenVAT in the viewport. 3. Export this preview model to glTF format.

Export Notes

• Materials: Models extracted directly by the OpenVAT tool often have stripped material data. We recommend exporting the generated preview model as glTF to maintain material slots.
• glTF Settings: When exporting the glTF, ensure the following data is EXCLUDED (unchecked):
  • Animation Data
  • Skinning Data

License

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.