rwmicro

rwmicro is a lightweight C++ library for generating random-walk microstructures—binary patterns created by a periodic random walk.

Random walk microstructures produce expressive, diverse, and always-connected material layouts that are ideal for metamaterial design and learning structure–property relationships. This library is used in our paper:

Samuel Silverman, Dylan Balter, Keith A. Brown, Emily Whiting
Random-Walk Microstructures for Differentiable Topology Optimization
Proceedings of the ACM Symposium on Computational Fabrication (2025)

Dependencies

• C++17 or later
• Catch2 v3 (optional, for testing)
• OpenMP (optional, for example applications)

Building

git clone https://github.com/samsilverman/rwmicro.git
cd rwmicro
mkdir build && cd build
cmake ..
make -j8

The recommended way to use rwmicro is to vendor it directly (e.g., as a git submodule) and add it to your build with:

add_subdirectory("path/to/rwmicro")
target_link_libraries(your_target PRIVATE rwmicro)

Library Compile Flags

CMake Flag	Default	Description
RWMICRO_BUILD_TESTS	OFF	Build test suite.
RWMICRO_BUILD_APPS	OFF	Build command-line applications.
RWMICRO_USE_OPENMP	OFF	Enable OpenMP parallelism in command-line applications.

These flags are set in the cmake line:

cmake .. -DRWMICRO_BUILD_APPS=ON ...

For convenience, a build.sh script is included for building with compile flags:

./build.sh

Minimal Example

#include <cstddef>
#include <iostream>
#include <rwmicro/rwmicro.hpp>

int main() {
    const std::size_t nx = 5;
    const std::size_t ny = 5;
    const std::size_t targetMass = 15;

    rwmicro::Grid grid(nx, ny);
    rwmicro::grow(grid, targetMass);
    const bool valid = rwmicro::validate(grid);

    std::cout << "Microstructure:\n" << grid << std::endl;
    std::cout << "Valid: " << valid << std::endl;

    rwmicro::save(grid, "microstructure.csv");

    return 0;
}

Documentation

Documentation for all functions is provided through Doxygen-style docstrings. Command-line tools in apps/ demonstrate complete example workflows.

Applications

Build and run the provided command-line tools:

mkdir build && cd build
cmake -DRWMICRO_BUILD_APPS=ON ..
make -j8
./apps/<app_name>

See the apps README for more details.

Tests

Build and run the test suite:

mkdir build && cd build
cmake -DRWMICRO_BUILD_TESTS=ON ..
make -j8
./tests/rwmicro_tests

Contributing

Contribution guidelines are provided in CONTRIBUTING.md.

Maintainers

• Sam Silverman - sssilver@bu.edu

Citation

@inproceedings{Silverman:2025:RandomWalkMicrostructures,
author = {Silverman, Samuel and Balter, Dylan and Brown, Keith A. and Whiting, Emily},
title = {Random-Walk Microstructures for Differentiable Topology Optimization},
year = {2025},
isbn = {9798400720345},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3745778.3766645},
doi = {10.1145/3745778.3766645},
booktitle = {Proceedings of the ACM Symposium on Computational Fabrication},
articleno = {25},
numpages = {11},
keywords = {microstructures, random walks, inverse design, neural networks, homogenization},
location = {},
series = {SCF '25}
}

License

Released under the MIT License.