3D Computer Graphics short films for communicating cultural heritage An open source pipeline Francesca Delli Ponti, Daniele De Luca, Antonella Guidazzoli, Silvano Imboden, Maria Chiara Liguori CINECA Casalecchio di Reno, Bologna, Italy
[email protected] Abstract—Computer generated movies are one of the most popular media for edutainment but their complexity makes them impractical for many small and medium sized institutions. In this presentation, Cineca shares the experience of producing its first short movie, “Apa the Etruscan”, which led to the creation of a complete production pipeline made mostly out of open-source components.
character called “Ati”, meaning “mother” in Etruscan, in continuity with “Apa”, which means “father”. During the first movie a production pipeline inspired by the “Big Buck Bunny” short movie [6] was devised, balancing the need for high philological standards with the restraints of a short movie production completely developed using computer graphics. A year later, when the production of “Ati” started, the pipeline underwent a profound rearrangement. Paragraph III will explain the successive improvements made to the pipeline. We will see in paragraphs IV and V that our pipeline is mostly based on free open-source tools. The benefits of using open source tools go beyond the obvious fact that they are free. The web provides lively communities eager to share detailed knowledge on the tools, easing the learning curve and allowing for fast bug-fixing and adaptation to specific requirements. The open file format eases the sharing and reuse of previous work. Paragraph IV will show how using a free-available character rig allowed us to drastically cut down the production cost. Paragraph VI will highlight the importance of open-source in the field of digital preservation.
Keywords—Production pipeline, Cultural Heritage, Story-telling, 3D modelling, Open Source, Character design.
I. INTRODUCTION A movie production pipeline is a combination of people, tools and procedures. Theoretical information about how to manage such a production can easily be found on-line but information quickly becomes scarce when going from theory to practice to the extent that there is almost no documentation about the internal proprietary tools developed by each big commercial production. This paper shares in information about how we at Cineca [1] set up a production pipeline that actually worked, enabling us to successfully finish our first short movie and start its spinoff. II. TWO 3D CG SHORT MOVIES: “APA THE ETRUSCAN” AND HIS “COUSIN” ATI In 2012 the new Museum of the History of Bologna presented, as part of its cultural offer, “Apa the Etruscan at the discovery of Bologna”, a 3D stereoscopic movie dedicated to 2700 years of Bolognese history [2]. Conceived and realised at Cineca in a two year project involving about 20 people, the 15 minute long movie, developed entirely using Computer Graphics, goes through four different geo-referenced scenarios and six historical periods. “Apa” gained international recognition [3, 4] and was praised by several museum curators. This success led to a new project and a spin-off. As part of the collaboration between the Museum of the History of Bologna and Villa Giulia National Etruscan Museum in Rome [5] for a twin temporary exhibition to be held in Bologna and Rome in Autumn 2014, it was decided a follow-up to “Apa the Etruscan” should be made in order to tell the public something about the Southern Etruscan region and its findings with a new leading “actor”. This time, it was decided to have a female
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Fig. 1. A frame from “Apa the Etruscan” movie.
III. THE PRODUCTION PIPELINE OF THE SHORT MOVIE APA Producing edutaining movies for Cultural Heritage purposes is not, in principle, that different from producing any
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other kind of movie. What sets this kind of film-making apart is its purpose, in low budgets and in its language, which must be carefully chosen to please both the general public, including children, and experts in the field. There is also the need to ensure scientific accuracy. This is done by involving a number of Cultural Heritage professionals in order to provide reference materials, supervise model crafting and review the work with respect to their particular expertise. Realising even a short movie is a huge amount of work and the producers must take care to understand the dependencies among the work stages in order to maximize the parallelism among different teams. We arranged our work-flow to have 4 different teams working at the same time (Fig. 2).
supercomputer PLX [10], with its web interface based on Django [11], and of the production Blog with Wordpress [12]. To co-ordinate all of the people involved, we used a spreadsheet shared on GoogleDocs. Each line of the spreadsheet represents a movie shot, columns represent a different task, and cells are colour coded to convey the status of each task. One of the columns indicates who is working on each shot and also serve to avoid having more than one person working on the same asset at the same time (Fig. 4). Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig. 8. Fig. 9. Fig. 10.
Fig. 2. Team Production workflow.
Fig. 11.
As shown in Figure 3, the heart of our Pipeline is Blender [7], which provides the core functionalities.
Fig. 12. Fig. 4. Spreadsheet colour scheme.
Figure 5 shows the machine working. Artists checked daily for pending tasks, chose one by marking it with a “working” tag and retrieved and locked the required asset. After finishing, the assets were returned and unlocked and marked by the artists as in “revision”. Technicians checked for tasks to be revised then rendered the affected shots on the RenderFarm and, if necessary, presented technical problems to the artists. Periodically, directors and heritage professionals reviewed the latest rendered shots and, inside the weekly review meeting, gave directions and, eventually, generated new tasks. Fig. 3. Blender Production pipeline.
With the crew being geographically distributed, we arranged each member’s work through the Internet. Three online repositories were set up. The first one was for storing the preproduction documents: Storyboard, Animatic, and all the reference materials. This was made accessible using WebDAV [8]. A second repository hosted all the production files, often referred to as “Assets”, and was version controlled using SVN [9]. The third hosted the rendered frames and each movie shot and was manually versioned to keep only the latest few versions of each frame. Further technical steps included the set up of a Blender RenderFarm on the Cineca Fig. 5. The complete workflow
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IV. WORKING WITH BLENDER
Blender tools, modifiers and curves, in particular, substitute and optimise modelling process. Substantial changes in the appearance of the character, can be easily managed. The “Apa” movie had very few secondary characters and the majority where just billboards. With FlexRig models, the creation of secondary characters is quick, realistic and efficient. For example, a walkcycle can be applied to multiple FlexRig characters. Therefore, for “Ati” several 3D avatars will populate the scene concurrently.
An advantage to using open software such as Blender is its lively community. It not only helps in solving problems by offering an open forum for discussing ideas and solutions but has produced an already significant array of 3D models under Creative Commons licences. The personal blog of some of the greatest Blender artists share a lot of material that, in a community of users still as limited as that of Blender, is almost incredible. The growth of forums and blogs has been so huge that, since 2009, BlendSwap [13], a new resource specifically dedicated to downloadable files, has been made available to the community. The models available on BlendSwap are usually free, mainly under Creative Commons licenses, and heterogeneous, such as 2D/3D resources for game engines, optimised models for the “Internal” or “Cycles” render engines, materials, shaders, scripts and tools. All of the content, from textures to complete videogames, is incorporated in the “.blend” open format. For the development of “Ati”, we exploited this wealth of ready-made models, which were not available with such extent and quality only a couple of years ago when we were realising Apa. There is an additional advantage to using the characters available on BlendSwap: the rigging. BlendSwap comes with the useful tool Cookie Flex Rig, with CC-BY licence [14], which is a suite for creating characters that can be personalised in every detail: length and dimension of limbs and bust, skin and filament colour and so on. There are also sets of models with swappable hair and clothing. It is, thereby, possible to create drastically different characters with limited effort. The tool is available with the rigging, ready for animation and production. Ati, the main character, was created by adapting a character produced by the team from CGCookie and available on BlendSwap (Fig. 6). The model was complete, with the weight painted mesh associated to the armature for animation and shapes for rigging, which are used by animators as "pliers" connected to the bones that make up the armature. This has facilitated and sped up the technical work of setting up the character and cut its costs by 20%. For the character body we skipped the traditional 2D sketch stage and started directly in 3D, using the high-level tools provided by FlexRig.
V. LASER SCANNING ACQUISITIONS Ati’s short movie, dedicated to the Southern Etruscan region, is set at the National Etruscan Museum of Villa Giulia and at the temple of Veii during present and Etruscan period. The need of virtually reconstructing some halls of the museum and some Etruscan findings has led to the extensive use of scanner laser technology. Laser scanner acquisitions have been carried out for all the archaeological findings pertaining to the museum rooms dedicated to Veii and for the rooms themselves in order to use them in the virtual reconstruction of Ati's environment. For “Ati” at least two thirds of the 3D models will come from the laser scanner campaign, while in “Apa” less than 3% of the 380 blender files came from laser scanner acquisitions. The operations that are to be done on laser scanner acquisitions can be summarised thus: cleaning the noise, creating a mesh from the point cloud and adding a texture mapping of the mesh by using photos of real objects. Usually laser scanners rely upon their own software for processing the acquired data; in particular the laser scanner available at Cineca uses PolyWorks [15], which is not an open source software. The open alternative to PolyWorks is MeshLab [16], which was used in particular for the texture mapping and, when necessary, for the simplification of the meshes. From this point onward, the work can be continued with Blender.
Fig. 7. An example inside GIMP of the different overlapping layers: the blue one coming from Blender (displace map used as spatial reference), the other showing restored colour patterns and composition. The lower image, starting from left: the virtual restoration, the texturised scanner laser model and the wire frame of the mesh coming from laser scanner
Fig. 6. Character design: hair, make-up and face details adapted by following the iconography and references given by the archaeologists and adapted from a CGCookie free character. Currently under development.
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The archaeological findings from the temple of Veii were virtually restored by giving them the original colour. The MeshLab models were imported into Blender and a Displace Map of all of them was generated to serve as a reference guide for the patterns, in order to keep patterns similar to those of the archaeological findings. The coloured texture was created with Gimp: the use of different layers helps this virtual restoration by overlapping the Displace Map with the different patterns drawn and painted with Gimp’s tools. The resulting texture was used for the models of the Etruscan period and to complete the virtual restoration [Fig. 7].
a continual collaboration with external specialists for animation, music, sound and final editing; the inclusion of Laser Scanning and Photogrammetry experts, producing an increased model crafting speed and model quality; benefit from the continuous improvement of Blender, in particular for modelling, animation and rendering; consolidation of our custom software tools, aiming to integrate the Asset Manager, the Task Manager and the RenderFarm. In the future, we foresee the Open Source release of this work; addressing the need for archiving the Assets once a project is complete. This will rely on a Digital Library, supporting metadata and semantic search. Future plans aim at consolidating skills, tools and procedures in order to deal with the technical aspects of the process more systematically, further optimising the time and costs of production. Once those technical solutions are in place, we would like to invest more in story-telling, effective communication, enjoyability of the final product, with the aim of rapidly creating quality products for edutainment.
VI. DIGITAL PRESERVATION Preserving, re-using and sharing production assets is one important way to lower costs and exploit good quality models as much as possible, in particular the laser-scanner ones. Therefore, when a project is completed, it is a very good idea to store its results, grant their preservation and, eventually, share them. In case of static models, thanks to open-source-format, preservation is easier than in case of complex files, containing rigs, animations or special effects. These files can usually be opened only with the specific tools used to create them; with commercial tools, after some years, it might become impossible to recreate the environment for running them. Open source in general overcomes the problem of licenses and Blender, specifically, offers significant characteristics, such as a file format that is backwards and forwards compatible, compatibility with every operating system and a size on disk that is small enough to allow the tools themselves to be stored together with the data. Embracing the open data philosophy, the models created for “Apa” have been shared on the open data platform of Bologna Municipality [17] using a 3.0 CCBY SA NC licence and the models we are creating for Ati will follow. Once data are stored in a Digital Library, metadata ease their retrieval and deliver useful information, such as the “asset history”. For this purpose, we are developing a new service that will support viewing and adding asset Metadata during production. The Metadata scheme will be defined on a per project basis by the project leader and it will be possible to use a free-scheme or a known scheme already supported by the chosen Digital Library. In the latter scenario, the Digital Library ingestion procedure will be greatly simplified.
REFERENCES [1] Cineca (www.cineca.it) [2] Museum of the History of Bologna (http://www.genusbononiae.it/index.php?pag=25) [3] FIAMP 2012 (http://network.icom.museum/avicom/festivalfiamp/palmares-1996-2012/) [4] G. Boetto Cohen, L. Calori, F. Delli Ponti, T. Diamanti, A. Guidazzoli, S. Imboden, M.C. Liguori, A. Mauri, A. Negri, S. Pescarin, “Apa the Etruscan and 2700 years of Bolognese History”, in ACM SIGGRAPH ASIA 2011, Posters and Sketches Proceedings, Hong Kong, 2011. [5] Villa Giulia National Etruscan Museum in Rome (http://villagiulia.beniculturali.it) [6] Big Buck Bunny (http:// bigbuckbunny.org) [7] Blender (http://www.blender.org/) [8] WebDAV (http://www.webdav.org/) [9] SVN (http://subversion.apache.org/) [10] PLX Cluster (http://www.hpc.cineca.it/hardware/ibm-plx) [11] Django (https://www.djangoproject.com/) [12] Wordpress (http://www.wordpress.org) [13] BlendSwap (http://www.blendswap.com/) [14] Cookie Flex Rig (http://cgcookie.com/blender/2012/12/14/cgcookie-flex-rig-download/) [15] PolyWorks (http://www.innovmetric.com) [16] MeshLab tool (meshlab.sourceforge.net/) [17] Open data platform of Bologna Municipality (http://dati.comune.bologna.it/3d)
VII. CONCLUSIONS Two years after our first experience in the production of a CGI Short Movie, we are now facing a new project. Comparing the two productions, we are glad to report that several improvements have been contributed to our production pipeline, summarised hereafter: a consolidated staff with specific Blender competences; a reduced need for external rigging and stereography specialists;
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