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Python: "Robust Reconstruction of Watertight 3D Models ..."

This is a Python implementation of the paper "Robust Reconstruction of Watertight 3D Models from Non-uniformly Sampled Point Clouds Without Normal Information" by A. Hornung and L. Kobbelt.

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TL;DR

The goal is to create a watertight mesh from a point cloud.

The core idea is that the watertight mesh is the the minimum of a 3D distance function ϕ to the points.

The paper proposes a minimum solver that solves the minimum of that distance function ϕ by using a max-flow min-cut through a voxel grid.

Examples

There are online interactive renders at: https://mickare.github.io/Robust-Reconstruction-of-Watertight-3D-Models/

How it works

  1. A low resolution voxel grid is filled via a point cloud.
  2. A boolean crust is created by dilation & flood-filling until a watertight voxel crust is created.
  3. The float distance values ϕ of each crust voxel to the model point cloud is computed via diffusion of the point cloud.
  4. A weighted graph of ϕ is created from the outer crust surface to the inner crust surface. The Maxflow-Mincut of this graph is the minimum of ϕ.
  5. Either:
    • Repeat from 3. in a higher resolution by dilating the mincut to a new crust
    • Finally extract and smooth a mesh from the mincut

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Requirements

Python 3.8

Conda environment that has numba installed.

Some files are not in the official conda channels, so they need to be installed via pip.

  • pip install -r requirements.txt

Usage

Run:

  • main.py for running the reconstruction and show each step in the browser
  • export.py. for exporting a web page with each reconstruction step

Point clouds

Switching the point cloud model

Change the following line in either main.py or export.py.

example = Example.BunnyFixed

Available point clouds

Name Description Source License
Bunny Stanford Bunny https://graphics.stanford.edu/data/3Dscanrep/ Free but acknowledge required.
BunnyFixed The Bunny with addition points https://graphics.stanford.edu/data/3Dscanrep/ Free but acknowledge required.
Dragon Stanford Dragon https://graphics.stanford.edu/data/3Dscanrep/ Free but acknowledge required.
Camel From another paper https://people.csail.mit.edu/sumner/research/deftransfer/data.html De Espona model library
Cat Free cat model https://free3d.com/3d-model/lowpoly-cat-rigged-run-animation-756268.html Personal Use License
Dog Free dog model https://free3d.com/3d-model/low-poly-german-shepherd-dog-26963.html Personal Use License

Custom point clouds

You can use your own models. This project has model loader implemented for .ply and .pts files. Point clouds (like Cat and Dog) can be generated from existing wavefront .obj meshes.

Code

Voxel Data Structure

We split the voxel space into chunks, which we stored in a flat dict which we call ChunkGrid. Both Chunk and ChunkGrid have a fill value which is used in the case of a filled or missing chunk. The standard math (+, -, /, *, ...) and logical (&, ^, |, ...) operators are implemented for both Chunk and ChunkGrid, and are forwarded to the internal numpy arrays or fill values.

The chunk size N³ (e.g. 16x16x16) can be configured in main.py or export.py.

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You can find the data structure in data/chunks.py.

Plotting

Plotly is used for plotting the 3D point clouds, meshes and voxels.

The voxel mesh is created in render/voxel_render.py. It reduces the number of triangle faces by merging neighboring voxel faces.

Contributors

License

The code in this repository is licensed under the MIT License.

The models and point clouds are each licensed from a third party and are not part of this license! You should NOT distribute or use these models against their license. A list of the used model licenses and source is at models/README.md.