draco_decoder

draco_decoder is a Rust library for decoding Draco compressed meshes. It provides native and WebAssembly (WASM) support with efficient bindings to the official Draco C++ library.

Overview

• Native:
  The native part uses cxx to create safe and ergonomic FFI bindings that directly connect to Draco's C++ decoding library. This allows efficient and zero-copy mesh decoding in native environments.

• WASM:
  For WebAssembly targets, draco_decoder leverages the official Draco Emscripten build. It uses a JavaScript Worker to run the Draco decoder asynchronously, enabling non-blocking mesh decoding in the browser. The JavaScript implementation is available in a separate repository:
  https://github.com/jiangheng90/draco_decoder_js.git

This design provides a unified Rust API while seamlessly switching between native and WASM implementations under the hood.

build guide

• install essential for cpp develop (cmake, cpp compiler, ..)
• cargo build

now it has passed all lateast platform build. but I'm not sure how to make installation guide to fit all platform.

⚠️ Warning: This crate currently work in progress, I have not tested on many devices of building. now on windows it only support build on MSVC, and it may have some build issues.

⚠️ Warning: On wasm, due to the multi-threaded interaction between Rust and JS, encoded data will be copied once when transferring from Rust to JS. When multi-threaded Draco wasm completes decoding and passes it back to Rust, a second copy occurs. This process inevitably causes performance overhead. Since supporting SharedArrayBuffer in browser environments requires cross-origin isolation, currently this is the only viable solution.

native/wasm usage

async api

use draco_decoder::{DracoDecodeConfig, AttributeDataType, decode_mesh};

// some async wrapper

let mut config = DracoDecodeConfig::new(vertex_count, index_count);

// Add attributes to decode (dimention and data type)
config.add_attribute(dim, AttributeDataType::Float32);
config.add_attribute(dim, AttributeDataType::Float32);

// Your Draco-encoded binary mesh data
let data: &[u8] = /* your Draco encoded data here */;

// Asynchronously decode the mesh data
let buf = decode_mesh(data, &config).await;

// wrapper end

sync api

use draco_decoder::{DracoDecodeConfig, AttributeDataType, decode_mesh};

let mut config = DracoDecodeConfig::new(vertex_count, index_count);

// Add attributes to decode (dimention and data type)
config.add_attribute(dim, AttributeDataType::Float32);
config.add_attribute(dim, AttributeDataType::Float32);

// Your Draco-encoded binary mesh data
let data: &[u8] = /* your Draco encoded data here */;

// decode the mesh data
let buf = decode_mesh_sync(data, &config)

In certain cases, undecoded glTF primitive parameters are unreliable for configuring Draco, which can cause significant issues. To achieve zero-copy data, Rust must first allocate memory, but the required memory length cannot be determined through configuration. However, in Draco, obtaining the length would require a full decoding pass—resulting in two separate decoding operations. To address this, I designed a caching mechanism within the FFI that splits the decoding process into: decoding → generating configuration → allocating memory and copying data. The current decoding wrapper may still have some issues that need testing.

async api

use draco_decoder::{DracoDecodeConfig, AttributeDataType, decode_mesh_with_config};

// Your Draco-encoded binary mesh data
let data: &[u8] = /* your Draco encoded data here */;

// Asynchronously decode the mesh data
let MeshDecodeResult{data, config} = decode_mesh_with_config(data).await;

// config is origin decodeconfig

// wrapper end

sync api

use draco_decoder::{DracoDecodeConfig, AttributeDataType, decode_mesh_with_config_sync};

// Your Draco-encoded binary mesh data
let data: &[u8] = /* your Draco encoded data here */;

// decode the mesh data
let MeshDecodeResult{data, config} = decode_mesh_with_config_sync(data, &config)

Performance

The performance of draco_decoder has been measured under different environments: