Stroke Transfer: Example-based Synthesis of Animatable Stroke Styles

This repository contains the published code for the paper "Stroke Transfer: Example-based Synthesis of Animatable Stroke Styles".

Dependencies

The project was developed using Python 3 (Anaconda environment) with the following packages.

[Anaconda default packages]

• NumPy
• SciPy
• matplotlib
• PyQt5

[Additional dependencies]

• OpenCV
• PyOpenGL
• glumpy
• point cloud utils
• libigl
• pydec
• h5py
• imageio (OpenEXR format)
• tqdm

Quick Start

We provide example assets (e.g., "assets/monkey") for demo usage (you can quickly test the pipeline).

assets/monkey

Exemplar	Reference Rendering	Stroke Rendering

assets/deforming_sphere

Exemplar	Reference Rendering	Stroke Rendering

Asset Structure

We have tested a workflow with the blender (3.0 or higher) for 3DCG asset preparation.

[src] single frame data mainly used for regression process.

• exemplar.png: exemplar image (.png) drawn by the artist.
• annotation.json: annotation file (.json) exported from annotation tool (0_annotation.py)
• texture.png: brush texture image used for stroke rendering.
• object_001.obj: 3D model data (.obj) exported from 3D CG software.
• camera_001.json: 3D camera parameter file (.json) exported from 3D CG software (blender/export_camera.py).
• diffuse_001.exr: diffuse image (.exr) exported from 3D CG software.
• specular_001.exr: specular image (.exr) exported from 3D CG software.

[target] animated sequences to apply stroke transfer.

• object/object_%03d.obj: 3D model data (.obj) exported from 3D CG software.
• camera/camera_%03d.json: 3D camera parameter file (.json) exported from 3D CG software (blender/export_camera.py).
• diffuse/diffuse_%03d.exr: diffuse image (.exr) sequences exported from 3D CG software.
• specular/specular_%03d.exr: specular image (.exr) sequences exported from 3D CG software.

If you are interested in preparing custom asset with the blender, please see the manual (3D CG Asset Preparation).

• camera parameters (.json).
• 3D model data (.obj).

The other diffuse or specular image can be generated with usual blender menus.

Usage

To run our pipeline, please first move to the target asset directory.

cd assets/deforming_sphere

Now you can run each pipeline (command line tool) to output stroke transfer result.

Command Line Tool Format

Each command line tool accepts a single XML file to configure the settings.

e.g. you can run smoothing process in the following manner.

python ../../python/3_smoothing.py xml/3_smoothing.xml

The XML includes input/output settings and parameters to change the results of the pipeline.

<?xml version="1.0"?>
<smoothing>
  <!-- input setting -->
  <orientation filename_template ="dst/transfer/orientation/orientation_%03d.json"/>
  <object filename_template = "target/object/object_%03d.obj"/>

  <!-- parameters -->
  <params lambda_temporal = "0.5" lambda_spatial = "0.07" deform = "True"/>
  <frames start = "1" end = "1"/>

  <!-- for visualization purpose -->
  <camera filename_template = "target/camera/camera_%03d.json"/>
  <diffuse filename_template = "target/diffuse/diffuse_%03d.exr"/>

  <!-- for debug -->
  <verbose on = "True"/>

  <!-- output setting -->
  <output orientation = "dst/smoothing/orientation/orientation_%03d.json" />

  <!-- internal data setting -->
  <internal dirname = "temp" overwrite="False"/>
</smoothing>

0_annotation.py (optional for demo usage)

If you want to make new annotations for the asset, please run the following command.

python ../../python/0_annotation.py xml/0_annotation.xml

You can annotate stroke orientations and width (length will be automatically computed) using a simple GUI and export annotation.json data (please see Annotation Tool Manual for more details).

1_regression.py

The regression process generates the new models for orientations, colors, length, and width in the output directory (in demo: dst/regression).

python ../../python/1_regression.py xml/1_regression.xml

2_transfer.py

The transfer process generates the transferred results of orientations, colors, length, and width in the output directory (in demo: dst/transfer).

python ../../python/2_transfer.py xml/2_transfer.xml

Orientation Transfer	Color Transfer	Width Transfer	Length Transfer

3_smoothing.py

The smoothing process generates filtered orientations with spatial and temporal regularization parameters in the output directory (in demo: dst/smoothing)

python ../../python/3_smoothing.py xml/3_smoothing.xml

4_anchor_points.py

This process generates the hierarchy of anchor points for stroke drawing process (in demo: dst/anchor_points).

python ../../python/4_anchor_points.py xml/4_anchor_points.xml

5_stroke.py

The stroke renderer will generate the stroke layer (without undercoat) and the final result (with undercoat) in the output directory (in demo: dst/stroke)

python ../../python/5_stroke.py xml/5_stroke.xml

Undercoat	Stroke (without undercoat)	Final (with undercoat)

Citing

If you find Stroke Transfer useful for your research or work, please use the following BibTeX entry.

@inproceedings{ST:2022,
        author = {Todo, Hideki and Kobayashi, Kunihiko and Katsuragi, Jin and
                        Shimotahira, Haruna and Kaji, Shizuo and Yue, Yonghao},
        title = {Stroke Transfer: Example-based Synthesis of Animatable Stroke Styles},
        booktitle = {SIGGRAPH '22 Conference Proceedings},
        year = {2022},
        pages = {1--10},
        numpages = {10},
        doi = {10.1145/3528233.3530703}
    }

License

This project is released under MIT License.