PicoVDB

Compact sparse volumetric data format optimized for WebGPU real-time rendering.

Live Demo →

Warning

This project is under active development. The data format and API are subject to change.

Overview

• 50%+ smaller volumes than NanoVDB (bunny: 64MB → 28MB)
• WebGPU-native data layout with WGSL shader library
• 32-bit addressing for better GPU compatibility
• Fast traversal with hierarchical raymarching (HDDA)

This repository includes:

• picovdb.wgsl - WGSL shader library
• picovdb.ts - TypeScript loader
• src/main.zig - NanoVDB → PicoVDB converter
• src/stl.zig, src/mesh2ls.zig - STL mesh → PicoVDB level set voxelizer

How It Works

PicoVDB compresses NanoVDB files through:

• Rank query compression: Bit masks + counts eliminate inactive voxel storage
• 32-bit offsets: Replace 64-bit pointers with computed indices (limits to 4 billion active voxels)
• GPU-aligned structs: Minimize padding, maximize cache efficiency

Usage

// Include the library in your compute shader
// (concatenate picovdb.wgsl with your shader code)

@group(0) @binding(2) var<storage> picovdb_grids: array<PicoVDBGrid>;
@group(0) @binding(3) var<storage> picovdb_roots: array<PicoVDBRoot>;
@group(0) @binding(4) var<storage> picovdb_uppers: array<PicoVDBUpper>;
@group(0) @binding(5) var<storage> picovdb_lowers: array<PicoVDBLower>;
@group(0) @binding(6) var<storage> picovdb_leaves: array<PicoVDBLeaf>;
@group(0) @binding(7) var<storage> picovdb_buffer: array<u32>;

@compute @workgroup_size(16, 16)
fn main(@builtin(global_invocation_id) global_id: vec3u) {
    let grid = picovdb_grids[0];

    // Initialize read accessor
    var accessor: PicoVDBReadAccessor;
    picovdbReadAccessorInit(&accessor);

    // Sample voxel data using HDDA traversal
    var hit_t: f32;
    var hit_value: f32;
    let hit = picovdbHDDAZeroCrossing(
        &accessor, grid, ray_origin, t_near, ray_direction, t_far, &hit_t, &hit_value
    );
}

Converting Files

# Build converter
zig build

# Convert NanoVDB to PicoVDB
./zig-out/bin/picovdb convert input.nvdb output.pvdb

# Voxelize an STL mesh directly to a PicoVDB level set (no OpenVDB required).
# --voxel is the voxel size in mesh units; repeatable --rotate-x|y|z flags
# apply in command-line order (e.g. -90 about X re-orients Z-up meshes to Y-up).
./zig-out/bin/picovdb mesh --voxel 0.05 --rotate-x -90 input.stl output.pvdb

Related Projects

• OpenVDB - Industry standard sparse volume library
• NanoVDB - GPU-optimized sparse volumes
• WebGPU NanoVDB - WebGPU port of NanoVDB