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Using a Combination of Micro–Computed Tomography,
CAD and 3D Printing Techniques to Reconstruct
Incomplete 19th-Century Cantonese Chess Pieces
S. D. LAYCOCK, School of Computing Sciences, University of East Anglia, NR4 7TJ G. D. BELL, East Anglian Radiography Research, Modelling and 3-D printing group, School of Science, Technology and Health, University Campus Suffolk, Ipswich, IP4 1QJ, 2UK N. CORPS, Bruker UK, Banner Lane, Coventry CV4 9GH D. B. MORTIMORE, Newbourne Solutions Ltd, Newbourne, Woodbridge, IP12 4NR, UK G. COX, East Anglian Radiography Research, Modelling and 3-D printing group, School of Science, Technology and Health -Suffolk, Ipswich, IP4 1QJ, 2UK S. MAY, School of Computing Sciences, University of East Anglia, NR4 7TJ I. FINKEL, The British Museum, Great Russell Street, London WC1B 3DG
As scanning technologies improve new approaches to digitizing cultural heritage artefacts emerge. The use of micro–computed tomography (micro-CT) presents an interesting approach as it is capable of high-resolution scans of not just the surface of the artifact but also the intricate internal structures and volumes leading to more complete digitization than is possible with traditional surface laser scanning techniques. In this work, we investigate the potential to digitize heritage artifacts using micro-CT and focus on the methods of interacting with the datasets to create digital restorations of broken and incomplete pieces before printing physical replicas using 3D printing technology. We visualize the virtual models with clear identification of the new portions added by a digital artist with reference to existing pieces and archives.
Categories and Subject Descriptors: I.4.1 [ Computing Methodologies ]: Image Processing and Computer Vision— Digitization and image capture ; I.3.5 [ Computing Methodologies ]: Computer Graphics— Computational geometry and object modeling
Additional Key Words and Phrases: Digitization, 3D printing, reconstruction, 3D modelling
ACM Reference Format: S. D. Laycock, G. D. Bell, N. Corps, D. B. Mortimore, G. Cox, S. May, and I. Finkel. 2015. Using a combination of micro–computed tomography, cad and 3D printing techniques to reconstruct incomplete 19th-century Cantonese chess pieces. ACM J. Comput. Cult. Herit. 7, 4, Article 25 (February 2015), 6 pages. DOI: http://dx.doi.org/10.1145/
1. INTRODUCTION
In our previous article [Laycock et al. 2012], we reported the combined use of x-ray micro-CT and 3D printing technology to study and then print a 19th-century Cantonese ivory chess piece with an
Authors’ addresses: S. D. Laycockl (Corresponding author); email: S.laycock@uea.ac.uk; G. D. Bell; email: duncan@ fishersideas.co.uk; N. Corps; email: nickcorps@yahoo.co.uk; D. B. Mortimore; email: david.mortimore@virgin.net; G. Cox; email: gcoxanimation@gmail.com; S. May; email: s.may@uea.ac.uk; I. Finkel; IFinkel@britishmuseum.org. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212) 869-0481, or permissions@acm.org. ©c 2015 ACM 1556-4673/2015/02-ART25 $15. DOI: http://dx.doi.org/10.1145/
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intricate internal structure due to its puzzle-ball base. Figure 1 shows the original Cantonese bishop used in our previous study. Large numbers of Cantonese ivory chess sets were produced in Canton between 1790 and 1910 for the European export market [Murray 1913; Hammond 1950; Wichmann and Wichmann 1964; Bell 1969, 1988; Finkel 2007]. Unfortunately, as these pieces are delicate and made up of several individual parts, as shown with the disassembled piece in Figure 1, many sets are now incomplete due to breakages and sometimes losses of some of the individual pieces or their constituent parts. In this article, we show how we can create complete Cantonese chess pieces based on utilizing micro-CT data of complete pieces, as shown in our digitization of a complete Cantonese ivory chess piece [Laycock et al. 2012]. Since the pieces have common elements, it is possible to use the accurate scans of one piece to aid in the reconstruction of another damaged or incomplete piece. This article describes the chess pieces used, the methods employed, and the results obtained. Where data is introduced such as for completing parts no longer in existence, images are provided to clearly identify these portions and references to sources of images of the pieces used by the digital artist are included.
- RELATED WORK
Scanning of human anatomy using CT is now commonplace, and these datasets have been used in- creasingly in the production of 3D prints to aid surgical [Esses et al. 2011] and interventional radio- therapy planning [Tam et al. 2013], as well as human physiology studies [Giesel et al. 2009]. Abel et al. 2011] summarized the possible role of x-ray micro-CT in the study, preservation and dissemination of knowledge relating to various artifacts. They compared and contrasted x-ray micro-CT and other meth- ods such as photography, serial sectioning, and laser surface scanning techniques and mentioned the possibility of linking the micro-CT imaging 3D data to 3D printer technology. Pitzalis et al. [2008] utilize CT to capture details present in the mineral structure of a cylinder seal. They also used opti- cal microtomography to obtain surface details with a precision of up to 0.1μm. In our previous article [Laycock et al. 2012], we did exactly that using a single complete 19th-century Cantonese ivory chess piece with an intricate internal structure. Guidi et al. [2014] investigated the importance of expert feedback during reconstruction to avoid misleading details.
- DESCRIPTION OF THE IVORY CHESS PIECES AND THEIR PROVENANCE
The artifacts used in this work had been in the possession of one of the authors’ (G.D. Bell) father, the late R.C. Bell [Bell 1969, 1988]. In this work, we used a complete Cantonese ivory bishop shown in Figure 1, the partially complete rook represented by an elephant with tower shown in Figure 2(a), and a partially complete Mongolian archer representing the knight, which is shown in Figure 2(b). The rook was missing its puzzle-ball base, and the knight was missing its base in addition to many intricate parts including parts of the arrows, the horse’s legs, and a base for the horse to stand on. The provenance of these three Cantonese chess pieces was worked out from looking at descriptive text, figures, and photographs in appropriate books [Murray 1913; Hammond 1950; Wichmann and Wichmann 1964; Bell 1969, 1988; Finkel 2007]. On this basis, the three pieces were identified as being parts of a bishop, rook, and knight. All three pieces were ivory colored; however, it is typical for opposing pieces to be stained red. The heights of the incomplete rook and knight ivory pieces were 7.12cm and 4.41cm, respectively, while the original complete bishop was 9.82cm high [Laycock et al. 2012].
- DIGITIZING THE CANTONESE CHESS PIECES, SEGMENTING THE PUZZLE BALL, AND CREATING THE 3D PRINTS OF THE RECONSTRUCTED STL FILES
The two incomplete chess pieces were scanned by one of the authors (N. Corps) using a SkyScan 1173 in vivo scanner. This scanner currently retails for approximately £ 250K, although it is possible to use
25:4 •^ S. D. Laycock et. al
Fig. 3. Images of the incomplete Cantonese rook and knight taken from the axial slices of the micro-CT scan and viewed in Disect software. (a) shows that the elephant and its upper base are carved from a single piece of ivory but the tower on its back, its flag, and the mahout are all made separately and are attached with small wooden pegs. (b) The knight is missing its legs and parts of the arrows as indicated by the white arrow.
Fig. 4. A photograph of a complete knight [Bell 1988] is presented in (a) with permission of Penguin Books. This image was used to guide the reconstruction of the missing parts. A rendering from ZBrush showing the reconstruction, with the red parts indicating the additions, is presented in (b). The remaining parts were acquired from the micro-CT data. (c) Images of 3D prints of the reconstructed knight. (d) Image of the 3D print of the reconstructed rook. These models were completed using the puzzle-ball base from the Cantonese bishop.
could then be imported into ZBrush (http://www.pixologic.com), a digital sculpting and painting pro- gram. ZBrush was used to digitally reconstruct the missing sections in a manner that mirrored the original carving process as it has some advanced mesh editing features. The reconstruction process took approximately 12 hours with the aid of reference images of the complete piece illustrated in Bell [1988] and shown in Figure 4(a). The original carvers were extremely skilled, although subtle geomet- ric differences in pieces can occur. Once the digital reconstruction was created, the authors discussed the resulting images with Dr C. Barclay, curator of the Oriental Museum at Durham University. The Oriental Museum currently holds a collection of Cantonese chesspeices left to them by the late R.C. Bell. The areas that were reconstructed were as follows: the horse’s legs, a support for them, the miss- ing tip on the arrow in the archer’s bow, and the quiver of a number of arrows. Then, using Maya, as with the rook, the now completed upper piece of the archer was again joined to the puzzle ball and base data acquired from the original Cantonese piece [Laycock et al. 2012]. Figure 4(b) shows the mounted
Digital Reconstructions from Micro-CT •^ 25:
archer where the sections shaded red indicate the parts created by the digital artist in ZBrush. The re- sulting model was converted back to an STL (now complete with its own puzzle balls and base) and was similarly sent to Shapeways Ltd. (http://www.shapeways.com) and printed in a polished white strong and flexible nylon material (see Figure 4(c)). Finally, a mirror image of the Mongolian mounted archer was produced by mirroring the geometry in a 3D modeling package. Both the normal mounted archer and its mirror image were then printed out in a powder-based material using a ZCorps 450 3D printer in approximately 2 hours. The printer has an accuracy of 0.13mm and currently retails at approxi- mately £ 30K. However, even more accurate printers could lead to better-quality reproductions in the future in a wide range of materials. 3D printing services provided by companies such as Shapeways Ltd. are particularly appealing.
- RESULTS AND DISCUSSION
We have shown it is possible to reconstruct whole Cantonese chess pieces with moving puzzle balls by performing x-ray micro-CT scans of damaged or incomplete pieces, producing highly detailed STL files, joining them to data previously acquired from a complete piece [Laycock et al. 2012], and then printing the resultant STL on a 3D printer. Unlike the original bishop chess piece [Laycock et al. 2012], we found no internal defects in the ivory of the new pieces shown in Figures 2(a) and 2(b). However, as can be seen in the 3D cut plane views shown in Figures 3(a) and 3(b), the micro-CT scans revealed the fact that although the chess figures themselves were made from a single piece of ivory, the tower, flag, and mahout of the rook and the arrow tip in the knight’s bow and the arrows in his quiver were made separately. This gives valuable insight into the methods used by the original Cantonese carver. The bishop is dressed as a mandarin in the style of the Manchu court (1644–1911). The knight ap- pears to be a mounted archer of a Mongolian warrior rather than a Chinese horseman. This is not unexpected as many of the Cantonese ivory puzzle-ball chess sets made between 1790 and 1910 had one side (often the red pieces) made as Chinese officials and military personnel, while the other (often the white side) were carved either as Western or alternatively Mongolian figures. With a normal mod- ern European set such as those of the Staunton type [Bermingham 1935], it would only be necessary to have six complete and undamaged pieces, that is, one pawn, one rook, one knight, one bishop, one queen, and one king chessman, to be able to reconstruct an entire set. Half would be of a darker color and the other half would be of a lighter color to represent black and white. In contrast, to make a complete Cantonese set, it would be necessary to have 12 pieces to make a complete set since the two sides are not only different colors (usually white and red) but also depicted as Chinese figures on one side versus either Western or Mongolian figures on the other. In the case of the Mongolian mounted archer, in order to make the horse’s legs strong enough, the front legs were given a support similar to those illustrated elsewhere (see Figure 238 on page 173 of Bell [1988]). With the ZBrush software, it was also possible to put some missing arrows into the mounted archer’s quiver and replace the missing tip one the arrow in his bow (see Figure 4(c)). The techniques we have shown could easily be adapted by museums for repairing damaged artifacts or making accurate and pleasing reproduction models for sale or education purposes.
REFERENCES
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