Breaking Good: Fracture Modes for Realtime Destruction

This is the code accompanying the Transactions on Graphics paper "Breaking Good: Fracture Modes for Realtime Destruction", by Silvia Sellán, Jack Luong, Leticia Mattos Da Silva, Aravind Ramakrishnan, Yuchuan Yang and Alec Jacobson and the NeurIPS Datasets & Benchmarks 2022 paper "Breaking Bad: A Dataset for Geometric Fracture and Reassembly" by Silvia Sellán, Yun-Chun Chen, Ziyi Wu, Animesh Garg and Alec Jacobson.

Installation

To install this library, start by cloning this repository

git clone https://github.com/sgsellan/fracture-modes.git

Create a conda environment*

conda create -n fracture-modes python=3.9
conda activate fracture-modes

*for Apple Silicon (M1/M2) users, the igl, scikit-sparse, and tetgen conda packages are currently not available for arm64. To ensure that you create a x86_64 environment use instead

CONDA_SUBDIR=osx-64 conda create -n fracture-modes python=3.9
conda activate fracture-modes
conda config --env --set subdir osx-64  # make sure that conda commands in this environment use intel packages

Then, install all dependencies:

python -m pip install -r requirements.txt
conda install -c conda-forge igl scikit-sparse tetgen

Finally, obtain a (free if you're academic) mosek licence here, and install it as a python package:

conda install -c mosek mosek

You can validate your installation by running

python scripts/example.py

which should complete in around 15 seconds and return a verbose wall of text ending with "Example ran successfully!"

Once this is done,

Use for fracture simulation

You can use this library by adding this repository to your python path and importing fracture_utility. The following sample code will load a mesh and compute its fracture modes (see scripts/example.py):

import numpy as np
import igl
import fracture_utility as fracture
from gpytoolbox.copyleft import lazy_cage

# This is the "fine mesh", i.e. the mesh we use for rendering
v_fine, f_fine = igl.read_triangle_mesh("data/bunny_oded.obj")
v_fine = gpytoolbox.normalize_points(v_fine)
# This is the "cage mesh", i.e. the coarser mesh that we will tetrahedralize and use for the physical simulation
v, f = lazy_cage(v_fine,f_fine,num_faces=100)
# Tetrahedralize
tgen = tetgen.TetGen(v,f)
nodes, elements =  tgen.tetrahedralize()
# Initialize fracture mode class
modes = fracture.fracture_modes(nodes,elements) 
# Set parameters for call to fracture modes
params = fracture.fracture_modes_parameters(num_modes=10,verbose=True,d=3)
# Compute fracture modes
modes.compute_modes(parameters=params)

After running this code, the class attribute modes.modes will be populated with a 3num_tets by 10 matrix containing the displacements of each tetrahedron in the mesh (row) for each mode (column).

Any runtime impact can be projected into our computed modes to obtain a realtime fracture with modes.impact_projection; for example,

# We need to precompute some stuff that we will only need to do once
modes.impact_precomputation(v_fine=v_fine,f_fine=f_fine)
# Optionally, you can use this to save each mode's segmentation in the current directory
modes.write_segmented_modes("output_modes")
contact_point = nodes[1,:]
direction = np.array([1.0,0.0,0.0])
# First projection, this should be fast
modes.impact_projection(contact_point=contact_point,direction=direction)
# Second projection, this should be fast
new_contact_point = nodes[5,:]
modes.impact_projection(contact_point=new_contact_point,direction=direction)
# Write segmented output to obj
modes.write_segmented_output("output.obj")

We also provide a graphical interface that you can use to get a quick idea of how our algorithm works. Open it by running

python scripts/fracture_gui.py PATH/TO/FINE/MESH.obj

Your mesh will appear on screen surrounded by a coarse cage. You can tweak the size of the cage if you want using the slider. You can also change the number of modes you want to compute:

You can then press "Compute Modes". The console will show the progress, it shouldn't take more than one minute unless your cage is very fine. Once it is done, a message saying "Modes Computed" will appear. You can then press "Show Modes" to visualize all the possible fractures our modes identified:

Then, you can go to "Impact Mode", and click "Generate Random Impact". Three meshes will appear: one will show the norm of the impact as a scalar field on the cage mesh, the middle one will show the impact's projection onto our modes on the cage mesh, and the final mesh will be the fine mesh, segmented to show the pieces it would break on according to our algorithm with that given impact. Timing details will also appear on screen

Optionally, you can now press on "Save segmented output" to write the fine output to an .obj file. See assets/sample_use.mp4 for a full recorded GUI example.

Use for fracture dataset generation

As shown in our paper "Breaking Bad: A Dataset for Geometric Fracture and Reassembly", our code can also be used to simulate many fractures for a specific object. The documented funcionality necessary to replicate our dataset generation can be found inside the fracture_utility/generate_fractures.py function. An example use can be found in the scripts/example_dataset_generation.py script:

# Load dependencies
import fracture_utility as fracture
import sys
import os
# Read input mesh
filename = "data/bunny_oded.obj"
if len(sys.argv)>1:
    filename = sys.argv[1]

# Choose output directory
output_dir = os.path.splitext(os.path.basename(filename))[0]

# Call dataset generation without volume constraint and with a 5000 cage size.
fracture.generate_fractures(filename,output_dir=output_dir,verbose=True,compressed=False,cage_size=5000,volume_constraint=0.00)

Known Issues

Please do not hesitate to contact me if you find any issues or bugs in this code, or you struggle to run it in any way.

Licensing

This code is released free for academic, non-commercial, non-military use. Contact the authors for commercial usage licensing.