stl2sdf.jl

A Julia package for converting STL triangular surface meshes to implicit geometries defined by Signed Distance Functions (SDFs). Provides simple SDF computation with raycasting-based sign detection, RBF smoothing, and artifact removal capabilities. For usage examples, see test/Examples/.

Features

• STL Import: Handles both ASCII and binary STL formats with automatic duplicate vertex removal
• SDF Computation: Exact distance calculation with KD-tree acceleration for spatial queries
• Sign Detection: Robust raycasting with adaptive sampling and BVH acceleration
• Artifact Removal: Connected components analysis to eliminate small disconnected regions
• RBF Smoothing: Radial Basis Function interpolation/approximation for geometry refinement
• ParaView Export: VTI format output with distance fields for visualization

Installation

# From Julia REPL, press ] to enter package mode
pkg> add https://github.com/jezekon/stl2sdf.jl

or

git clone https://github.com/jezekon/stl2sdf.jl

Main Function

Convert STL mesh to signed distance function:

stl_to_sdf(stl_filename::String; options::Options = Options())

Parameters

• stl_filename::String: Path to input STL file (ASCII or binary)
• options::Options: Configuration options (optional)

Return Value

• Tuple: Empty tuple (results saved to disk as VTI files)
• Output files:
  • {name}_sdf.vti: Original SDF on coarse grid (always generated)
  • {name}_fine_sdf.vti: Smoothed SDF on refined grid (only if smoothing enabled)

Options

Configure the SDF generation with the following parameters:

options = Options(;
    smoothing_method = nothing,            # :interpolation, :approximation, or nothing (default: no smoothing)
    grid_refinement = 1,                   # Grid refinement factor (1 or 2)
    cell_size = nothing,                   # Grid cell size (nothing = interactive)
    remove_artifacts = false,              # Remove small disconnected components (default: false)
    artifact_ratio = 0.01                  # Min component size (fraction of largest)
)

Option Details

• smoothing_method: RBF smoothing approach
  • nothing - No smoothing (default)
  • :interpolation - Preserves exact SDF values at grid points
  • :approximation - Smoother results, may modify values
• grid_refinement: Output grid resolution multiplier (1 = same as input, 2 = double)
• cell_size: Explicit grid spacing (if nothing, prompts interactively based on mesh analysis)
• remove_artifacts: Enable connected components cleanup for noisy meshes
• artifact_ratio: Keep components ≥ this fraction of largest component size

Example Usage

using stl2sdf

# Basic usage with interactive grid setup
stl_to_sdf("Data/Bunny.stl")

Advanced Usage Examples

For complete examples, see test/Examples/:

Basic Example

# Simple beam with default settings
julia --project=. test/Examples/01_basic_beam.jl

Complex Example

# With smoothing and artifacts cleanup
julia --project=. test/Examples/02_complex_artifacts.jl
julia --project=. test/Examples/03_manual_sdf.jl

Visualization in ParaView

1. Load the output VTI file in ParaView
2. Add Contour filter
3. Set Isosurfaces value to 0.0 to visualize the zero-level (surface)

For distance field visualization:

1. Select Point Gaussian to show signed distance values
2. Color by distance field
3. Adjust color scale if needed

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Acknowledgments

This package implements SDF generation for implicit geometry representation. Built on MeshIO.jl for mesh I/O, ImplicitBVH.jl for ray tracing acceleration, and NearestNeighbors.jl for spatial queries.