Multi-view Wire Art

Siggraph Asia 2018

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Author: Kai-Wen Hsiao, Jia-Bin Huang, Hung-Kuo Chu

By: 藍晧

Outline:

• Introduction & Abstract
• Methods
• Results
• Evaluations
• Limitations
• Conclusion
• References

Introduction & Abstract�

Introduction and abstract (1)

• The use of wire as a medium for sculpturing has been widely applied to furniture design [Postell 2012], crafting wire wrapped jewelry [Iarussi et al. 2015; WigJig 2015], and wire sculptural art.
• French artist Matthieu Robert-Ortis has created compelling wire sculptures that exhibit two distinct image interpretation when viewed at different perspectives.
• The creation of multi-view wire sculpture is extremely time-consuming even by highly skilled artists

Introduction and abstract (2)

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• As the 2D projection of a 3D wire sculpture forms line drawing patterns, it is possible to craft multi-view wire sculpture art.
• Input: two or three line drawing images and the associated viewpoints provided by the user (user-specified)
• Output: Forms wire art that can be view from different views.

Methods�

Pre-processing

• Reconstruct a 3D visual hull — a set of voxels whose projections best approximate the reference images using the associated camera parameters.
• (1) Completeness: all the foreground pixels in the reference line drawings should be covered by the projections of the visual hull (Discrete Visual Hull)
• (2) Connectivity: the constituent voxels of the visual hull must form a connected component. (Connectivity Optimization)

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Visual Hull Reconstruction

Discrete Visual Hull Generation

Discrete Visual Hull

Connectivity Optimization

1. After extracting smooth and continuous 3D curves, then started to do curve skeleton from the visual hull.
2. Challenge: the process of visual hull reconstruction is performed locally and does not take into account the compactness of global structure, the extracted curve skeletons may contain many redundant parts with complex geometry.
3. Result to this problem: Perform a structure simplification on the curve skeleton to strike a balance between projection error and structure compactness.

3D Curve Extraction (1)

3D Curve Extraction (2)

Structure simplification:

Results�

Angels

Face

Evaluations�

Tradeoff between structure compactness and projection error

Comparison:

Limitations�

Results:

Speed: implementation may take up to several hours to construct a multi-view wire sculpture (depending on the chosen voxel resolution and input line drawing complexity)

Fabrication: The system does not incorporate any physical simulations. Therefore, we cannot guarantee the generated wire sculptures are 3D printable.

Conclusion�

• The core idea of our approach lies in reconstructing visual hull and extracting curve skeletons to balance projection error and spatial compactness.
• Can produce smooth and compact wire sculptures exhibiting multiple prescribed images with minimum distortions.

References�

• Structure-from-motion (SfM) [Schonberger and Frahm 2016; Snavely et al. 2006]
• Multi-view stereo (MVS) [Collins 1996; Furukawa and Ponce 2010; Goesele et al. 2007; Huang et al. 2018; Kuhn et al. 2017; Schönberger et al. 2016]
• Niloy J. Mitra and Mark Pauly. 2009. Shadow Art. ACM Trans. Graph. (Proc. of SIGGRAPH Asia) 28, 5 (2009), 156:1–156:7.
• A. Laurentini. 1994. The Visual Hull Concept for Silhouette-Based Image Understanding. IEEE Trans. Pattern Analysis Machine Intelligence 16, 2 (1994), 150–162.
• Luke Olsen, Faramarz F Samavati, Mario Costa Sousa, and Joaquim A Jorge. 2009. Sketch-based modeling: A survey. Computers & Graphics 33, 1 (2009), 85–103.
• Amit Bermano, Ilya Baran, Marc Alexa, and Wojciech Matusk. 2012. Shadowpix: Multiple images from self shadowing. In Comput. Graph. Forum (Proc. EUROGRAPHICS), Vol. 31. 593–602.