LEGO, a popular brick-based toy construction system, provides an affordable and convenient way of fabricating geometric shapes. However, building arbitrary shapes using LEGO bricks with restrictive colors and sizes is not trivial. It requires careful design process to produce appealing, stable and constructable brick sculptures. In this work, we investigate the novel problem of constructing brick sculptures from pixel art images. In contrast to previous efforts that focus on 3D models, pixel art contains rich visual contents for generating engaging LEGO designs. On the other hand, the characteristics of pixel art and corresponding brick sculpture pose new challenges to the design process. We propose a novel computational framework to automatically construct brick sculptures from pixel arts. This is based on implementing a set of design guidelines concerning the visual quality as well as the structural stability of built sculptures. We demonstrate the effectiveness of our framework with various bricks sculptures (both real and virtual) generated from a variety of pixel art images. Experimental results show that our system is efficient and gains significant improvements over state-of-the-arts.

Overview: (a) Given an input pixel art image, the system (b) applies image deformation to optimize the state of equilibrium (the original shape is shaded in light red); (c) adapts pixels’ color to standard LEGO color palette; (d) performs pixel level operations to resolve disconnected parts (modified pixels are highlighted in red); and (e) composes each layer using legal LEGO bricks to obtain the final brick sculpture (Input image: “Zapdos” © Pokémon Ltd).

Our framework can generate plausible LEGO brick sculptures from a large variety of pixel art images (see also supplemental material). (Top row) The input pixel art images. (Middle row) The balanced and color remapped 2D shapes. Note that three examples on the right are adjusted to keep balanced by expanding supporting lines (Pikachu and Hulk) or adding supporting strut (Saber). (Bottom row) The final brick sculptures (Input images: “Dragon” and “Hydra” © Heavy Cat Multimedia Ltd., “Popeye” © King Features Syndicate, Inc., “Spaceship” © Asmir Rogo, “Stone Gargoyle” © umrae, “Pikachu” © Pokémon Ltd, “Hulk” © Marvel Worldwide Inc., “Saber” © Manning Leonard Krull).

We are grateful to the anonymous reviewers for their comments and suggestions; and Ying-Miao Kuo for assisting the video production. The work was supported in part by the Ministry of Science and Technology of Taiwan (102-2221-E-007-055-MY3, 103-2221-E-007-065-MY3, and 104-2220-E-007-016), University of Bath startup fund, and EPSRC Grant EP/M023281/1.

@article{Kuo:2015:P2B,
author = {Ming-Hsun Kuo and You-En Lin and Hung-Kuo Chu and Ruen-Rone Lee and Yong-Liang Yang},
title = {PIXEL2BRICK: Constructing Brick Sculptures from Pixel Art},
journal = {Computer Graphics Forum (Proc. Pacific Graphics)},
volume = {34},
issue = {7},
year = {2015},
}