Contact me

Dear all,

It has been a few weeks since I have written any new articles, and that is because I have been away for family reasons. However, I am now back and hope to get new content out for you in the upcoming weeks.

In the meantime, I have noticed a spike in views on this blog and some of the readers have actually gotten in contact with me to ask questions. I think this is fantastic and would love to talk to anyone who has an interest in Visualisation. For this purpose, I wanted to share again my email address:

rbarratt01@qub.ac.uk

Feel free to get in contact for any reason, or feel free to comment under any of the articles I have posted.

Also, I will be attending a lot of conferences in the upcoming months. If you are at any of the following I’d love to chat! The conference I am attending are:

EAA Annual Meeting – Barcelona, 5th-8th September

CAA-UK – Edinburgh, 26th-27th October

Visual Heritage 2018 – Vienna, 12th-15th November

 

Finally, I have a number of publications in different stages, and will post updates as soon as they come out.

Hope to hear from you all soon,

Rob

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Alternative 3D Models: Multiple Vs Singular Interpretations

Wireframe

As part of my PhD project, over the last few months I have been researching trends in Visualisation from its incipit to today. I’m attempting to create a solid theoretical background upon which to build my own work, and in the process I am learning a lot of the philosophical and methodological foundations upon which 3D reconstruction stands.

There are many topics that I have found particularly interesting, some of which I have talked about before, and some of which I will write about in the near future. Today though I would like to concentrate on a topic I feel has only been discussed in passing: the creation of “alternative models”. Not only do I feel we need to dwell upon this subject more, I want to go against current trend to present a counterargument for their utility.

3D researchers have been advocating for alternative models from the start of Visualisation (Reilly 1992; Mathur 1997; Roberts and Ryan 1997; The Guardian 1999; Huggett and Guo-Yuan 2000). The basic idea is that it is impossible to present all hypotheses in a single 3D reconstruction, so a number of models should be reconstructed instead, each representing an alternative theory.

Alternative models fit within the general concept of accuracy. One of the major concerns with 3D reconstruction is the narrow scope for presentation of hypothetical data. Models are often built upon incomplete information, and as a result it is impossible to recreate a perfectly accurate representation of the past. There is a distinct worry amongst specialists and skeptics alike that without sufficient transparency 3D reconstructions may misinform and deceive an uninformed user (Bayliss 2003; Kensek et al. 2004; amongst many others). This concern is certainly founded, and while some suggestions have been put forward in an attempt to minimise the problem (Pang et al. 1997; Strothotte et al. 1999), the lack of a cohesive and enforced set of principles limits the reliability of 3D reconstruction as a methodology. We are moving in a positive direction, and publications such as the London Charter offer legitimisation of the use of these technologies (Beacham et al. 2006; Denard 2009). Yet there is still a need for enforced guidelines that can reduce, or at least explicitly state. inaccuracies.

The use of pink cement (Lock 2003), or Dell’Unto et al.’s (2013) levels of accuracy are good approaches to the problem, and the literature has embraced such ideas for the better. Alternative models, on the other hand, have been lurking in the background, often mentioned but never fully discussed. They are mostly used as an addendum or a failsafe, an attempt to silence any possible critic of the accuracy of the models. It is interesting how most of the publications that mention alternative models do not present alternative models themselves: papers concerned with the theoretical background use it as an example of ways to preserve accuracy, while technical papers omit alternative models altogether (with a few exceptions i.e. Roussou and Drettakis 2003). It is also important to note that they are always mentioned positively.

I would like to present a counterargument. I do not believe alternative models are bad, or that they have no uses. There are certainly occasions in which they can convey information more efficiently than other methods. I do however believe that they have a limited scope, and that using them as a way to present inaccuracies is counterproductive to the defining of a 3D methodology.

The limitations of alternative models can be expressed as so:

  • Physical and publication space managment
  • Time requirements
  • Multiple hypotheses representation

Physical and publication space management: using alternative models to present inaccuracies to the public or to fellow researchers requires for this information to be readily accessible. At present the issue with 3D documentation is one of space. Publications often do not possess enough space for a full documentation of the reconstruction process, and the problem is exacerbated in heritage management where information has to be tailored to an uninformed public. In most cases, the presentation needs cannot accommodate the presence of multiple models. Metadata and paradata are beginning to appear in publications through the use of online repositories, but the handling of multiple large models is still problematic.

Time requirements: 3D reconstruction is a process, which follows a number of steps. Work by Guidi et al. (2012; 2014) show an ideal example of the reconstruction procedure, with accumulative levels of detail and archaeological checks at the end of each phase. In order to reconstruct most alternative models, the split must occur right from the volumetric model. By doing so each variant must be constructed individually, or the subsequent changes must be reflected in each of the different models. Attempting to change the model in the later stages of production is still possible, but it requires more work, as there are more elements that need to be manipulated. Either way, the results is a distinct increase in the production time.

Multiple hypotheses representation: another logistical problem has to do with models with many conjectures. When is it necessary to create multiple models? If we are too strict with our definition of inaccuracies then every element in the reconstruction is in question. We would therefore end with numerous models with very subtle differences. On the other hand, if we we were too lax the purpose of using alternative models is void, as displaying only some of the hypotheses would render this process redundant. Additionally, if many hypotheses were to be displayed through alternative models, it would be necessary to create a model with every possible arrangement of hypotheses, exponentially increasing the number of reconstructions.

In addition to these limitations, my argument against the misuse of alternative models has to do with traditional methods of presenting archaeological data. Archaeological reports often attempt an objective analysis of the archaeological evidence, describing what has been found and trying to limit conjectures, frequently presenting multiple theories. Yet when interpreting an archaeological site, it is not uncommon to create a narrative. Certain evidence is omitted and new meaning is imposed on the remains, in an attempt to justify the current archaeological interpretation. Part of the scientific method is to present the data and propose a unifying theory, with the expectation that the theory shall change when new evidence comes to light. And archaeology subscribes to this view: while multiple scenarios may be presented in publication, there is often one preferred interpretation.

Therefore, in traditional archaeology the data is analysed to produce the results. Objective data is transformed into subjective interpretation, and with a change in the data comes a change in the interpretation. The uncertainty is accounted for in the source and not the output and the same should be true for 3D reconstruction. Metadata and paradata are paramount for the replicability of the process and for validating the hypotheses shown in the results. We must find better ways of preserving and presenting this form of information, to ensure the 3D methodology is valid. Alternative models however are part of the output, where subjectivity is allowed and even encouraged.

Critics often note that in Heritage Management the public is more susceptible to misinformation, making 3D reconstruction a ‘dangerous’ tool. Yet museum displays often present a single narrative, reducing complex archaeological issues to simplistic linear stories. While it is still a problem 3D reconstruction needs to address, the discussion has wider implications in the way we present data to the public.

Additionally, I am not saying that alternative models cannot have uses in archaeological presentation. In some cases the conflicting theories are at the core of the discussion, and alternative models help create a virtual representation of what this conflict appears like visually. A good example of this is the Patay-Horvath (2014) paper regarding the positioning of statues at the Temple of Zeus at Olympia. Here the alternative models are used effectively to communicate the main argument. It was however a deliberate choice from the author, and it had a specific purpose.

In conclusion, alternative models are not always the best option for presenting inaccuracies. While occasionally they can be effective in demonstrating conflicting hypotheses, in a wider methodology for 3D reconstruction they have little space. Presenting metadata and paradata still offers the best course for demonstrating uncertainty.

 

References:

Bayliss, R. (2003). Archaeological Survey and Visualisation: the View from Byzantium. Late Antique Archaeology Vol.1 No.1 pp.26-313.
Beacham, R. C., Denard, H. and Niccolucci, F. (2006). An Introduction to the London Charter. The E-volution of ICTechnology in Cultural Heritage.
Dell’Unto, N., Leander, A. M., Ferdani, D., Dellepiane, M., Callieri, M., Lindgren, S. (2013). Digital reconstruction and visualisation in archaeology: case-study drawn from the work of the Swedish Pompeii Project. Digital Heritage International Congress pp.621-628.
Denard, H. (2009). The London Charter: for the computer-based visualisation of cultural heritage.
Guidi, G., Russo, M., Angheleddu, D. and Zolese, P. (2012). A Virtual Connection between Past and Present: the Digital Revival of Cham’s Architecture (Vietnam). Virtual Systems and Multimedia pp.361-368.
Guidi, G., Russo, M. and Angheleddu, D. (2014). 3D survey and virtual reconstruction of archaeological sites. Digital Applications in Archaeology and Cultural Heritage 1 pp.55-69.
Huggett, J. and Guo-Yang, C. (2000). 3D Interpretative Modelling of Archaeological Sites/ A Computer Reconstruction of the Medieval Timber and Earthwork Castle. Internet Archaeology 8.
Kensek, K. M., Swartz Dodd, L. and Cipolla, N. (2004). Fantastic reconstructions or reconstructions of the fantastic? Tracking and presenting ambiguity, alternatives, and documentation in virtual worlds. Automation in Construction pp.175-186.
Lock, G. (2003). Using Computers in Archaeology: Towards virtual pasts. Routledge: London.
Mathur, S. (1997). Three Dimensional Representation of Archaeological Data in American Archaeology. Available at: https://web.archive.org/web/20000816044424/http://www.uiowa.edu/~anthro/plains/Termppr.htm. Last accessed: 31st Oct 2017.
Pang, A. T., Wittenbrink, C. M. and Lodha, S. K. (1997). Approaches to uncertainty visualisation. The Visual Computer pp.370-390.
Patay-Horvátz, A. (2014). The virtual 3D reconstruction of the east pediment of the temple of Zeus at Olympia – an old puzzle of classical archaeology in the light of recent technologies. Digital Applications in Archaeology and Cultural Heritage 1 pp.12-22.
Reilly, P. (1992). Three-dimensional modelling and primary archaeological data. In: Reilly, P. and Rahtz, S. Archaeology in the Information Age pp.92-107.
Roberts, J. C. and Ryan, N. (1997). Alternative Archaeological Representations within Virtual Worlds. In: Brown, R. 4th UK Virtual Reality Specialist Interest Group Conference – Brunel University pp.182-196.
Roussou, M. and Drettakis, G. (2003). Photorealism and Non-Photorealism in Virtual Heritage Representation. First Eurographics Workshop on Graphics and Cultural Heritage.
Strothotte, T., Masuch, M. and Isenberg, T. (1999). Visualizing Knowledge about Virtual Reconstructions of Ancient Architecture. Computer Graphics International.
The Guardian (1999). Megabytes of megaliths. 23rd September 1999.

How Video Games help present and interpret Neolithic Malta.

 

Hi all,

I gave a talk yesterday as part of Queen’s University Belfast PGR Talks. I had it recorded as I thought it would be interesting to share here some of my recent results.

I intended this presentation for those who may not be familiar with the topic, so it may be a bit vague at times, but it should provide a useful introduction to 3D reconstruction and gaming software.

Please feel free to share your thoughts and questions in the comment section.

Rob

Interpreting and Presenting Archaeological Sites Using 3D Reconstruction: Virtual Exploration of the Xaghra Brochtorff Circle in Gozo.

Unity 1.jpeg

Hi all,

Just as a heads up, I have uploaded my MPhil dissertation to Academia.edu, so go and check it out.

It’s available here.

It discusses 3D reconstruction in the Maltese islands, as well as using gaming software to analyse archaeological sites.

Feel free to comment here with any questions you may have. I’m hoping to increase communication on this platform this year!

 

Rob

Paper on Using Unity3D for Archaeological Interpretation

image paper.jpeg

Just a quick note to say that I have published an article for Archaeological Science: Reports regarding the use of a Unity3D script to calculate solar alignment at Ggantija, Gozo.

It is unfortunately not as open access as I would like, but I’ve been told that the article will be available for viewing for the next 50 days at https://authors.elsevier.com/a/1WFZO,rVDBK0IJ

If you have an interest in using 3D Reconstruction for analysis do check it out, and feel free to get in contact at rbarratt01@qub.ac.uk for more information.

Rob

Paul Reilly and the origins of 3D Reconstruction

Archaeology is all about looking at the past to understand the present, and in a similar guise to fully understand the basics of modern theory we have to delve into its origins. For this purpose, today I would like to take you back to 1989, when computer Visualisation was in its infancy.

The paper “Data Visualisation in Archaeology” by Paul Reilly (1989), and the later book “Archaeology and the Information Age” by Reilly and Rahtz (1992), were a crucial stepping stone for popularising 3D Reconstruction and introducing the theoretical background that is still important today.

3D Reconstruction saw its first applications in archaeology as early as 1985, when Woodward created a model of Roman Bath and of Caerleon, adapting software originally designed for industrial engineering (Smith 1985; Delooze and Wood 1991; Palamidese et al. 1993). Between then and 1989, a number of models had been created. Yet, the theoretical background was quite sterile, partly due to a division of roles between the researcher (archaeologist) and the modeller (computer designer).

Reilly’s paper “Data Visualisation in Archaeology” (1989) starts with a common problem in archaeology: the abundance of data. Due to the destructive nature of the excavation methodologies archaeologists resort to extensive recording of contexts, generating vast quantities of information in the process. Reilly demonstrates through examples what it it possible to achieve with this data. Apart from distribution maps which are more GIS territory, he uses examples of WINSOM models to demonstrate the potential for presentation of 3D modelling. More importantly, he argues that

“[Modelling] allows the researcher to demonstrate in strong visual terms how the interpretation relates directly to the collected data. […] it stimulates the researcher to look for further information. This may involve the application of extra analytical experiments on the existing data, or it may require the formulation of a completely new research design to answer the outstanding questions. – Reilly (1989) pp.577”

And

“[…] reconstructions require the modeller to define explicitly each and every element in the model and their spatial relationship to one another. The definition of the model forces the researchers to reconsider the original data, which can focus attention on problem areas and gaps, thus causing them to observe, or record differently, certain types of evidence in a future investigation. – Reilly (1989) pp.578“

These ideas are found again in a section Reilly contributed to Burridge et al. (1989), in which he argues that 3D Modelling can bring to light discrepancies in the original data.

Following “Data Visualisation in Archaeology”, Reilly published a series of articles that helped solidify his theories. Reilly and Shennan (1989) look at presentation, arguing that 3D navigation can help understand archaeological contexts by displaying large quantities of data in a small amount of time. “Towards a Virtual Archaeology” (1990) provides an overview of examples in 3D Reconstruction, and demonstrates the use in recreating monuments. It also outlines how this software could be applied to the teaching of archaeological excavation. In his 1991 contribution to Computing in Archaeology, he emphasises the importance for analysis and presenting, while also recognising that realistic models may lead to the assumption of “absolute truth”. Many of the concepts here expressed are still exceptionally relevant to modern theory, and have been debated by scholars for the three decades following Reilly’s publications.

His most important contribution is however “Archaeology and the Information Age”, edited with Rhatz (1992). This collection of truly fascinating articles are the founding stone for all future 3D Reconstruction, as well as other fields of digital media in archaeology. “Archaeology and the Information Age” explores the use of 3D for interpretation, arguing that pretty pictures should not be the main goal.  Through various examples, Reilly demonstrates the potential of 3D modelling for analysis, citing the reconstructions of Sulis Minervae, Bath and many others. Other authors in the book discuss issues of accuracy, simulation and subjectivity (I particularly enjoyed Molyneaux 1992).

Throughout the 1990s Visualisation saw an exceptional rise in popularity and the theoretical background developed in these years is still applicable today. Yet it all started with a handful of researchers, of which Reilly was the forefront (with the help of Shennan and Rahtz). If you are just starting to get into Visualisation, reading some of his works is a great place to start.

 

References:

Burridge, J. M., Collins, B. M., Galton, B. N., Halbert, A. R., Heywood, T. R., Latham, W. H., Phippen, R. W., Quarendon, P., Reilly, P., Ricketts, M.V., Simmons, J., Todd, S. J. P., Walter, A. G. N. and Woodwark, J. R. (1989). The WINSOM solid modeller and its application to data visualisation. IBM Systems Journal pp.548-568.
Delooze, K. and Wood, J. (1991). Furness Abbey Survey Project – The Application of Computer Graphics and Data Visualisation to Reconstruction Modelling of an Historic Monument. Computer Applications and Quantitative Methods in Archaeology pp.140-148.
Molyneaux, B. (1992). From virtual to actuality: the archaeological site simulation environment. In: Reilly, P. and Rahtz, S. Archaeology in the Information Age pp.192-198.
Palamidese, P., Betro, M. and Muccioli, G. (1993). The Virtual Restoration of the Visir Tomb. Visualisation pp.420-424.
Reilly, P. (1989). Data visualisation in archaeology. IBM Systems Journal 28(4) pp.569-579.
Reilly, P. (1990). Towards a virtual archaeology. In: Lockyear, K. and Rahtz, S. Computer Applications in Archaeology pp.133-139.
Reilly, P. and Rahtz, S. (1992). Archaeology in the Information Age. Routledge: London.
Reilly, P. and Shennan, S. (1989). Applying Solid Modelling and Animated Three-Dimensional Graphics. Surface And Solid Modelling and Image Enhancement pp.157-165.
Smith, I. (1985). Sid and Dora’s bath show pulls in the crowd. Computing pp.7-8.

 

Functionality vs Realism in 3D Modelling

I’m currently looking through the literature on 3D reconstruction as part of my PhD, and I thought I would share here some useful points I am gathering through this process. I’ve specifically been looking at publications prior to the year 2001, attempting to discover the ideas that created this field in the first place and the theoretical and technical background to the methodology. Many of the arguments I am encountering have strong resonance with today, and are crucial to understand present discussion.

One of the most interesting points I have come across is the debate between those who strive for realism in reconstruction, and those who reject it.

 

Realistic Modelling

‘Realist’ archaeologists are harder to spot, as the computer limitations of the time allowed for little realism. Collins et al. (1993), Burton et al. (1997), Novitski (1998), Worthing and Counsell (1999) and Addison (2000) strive for photorealism in their models, tacitly expressing the need for faithful models. Later authors such as Guttierez et al. (2006) and especially Chalmers (Chalmers 2002, Devlin and Chalmers 2001, Chalmers and Debattista 2009) have attempted to create absolute models through the careful reconstruction of the environment, as well as of the architecture itself.

 

Functional modelling

In earlier literature the advocates of a functional style are more vocal. Fletcher and Spicer (1992), Salisbury et al. (1994), Winkerbach and Salesin (1994), Lansdown and Schofield (1995), Miller and Richards (1995), Pang et al. (1997), Roberts and Ryan (1997) and Strothotte et al. (1999) express dissatisfaction with realistic models, preferring a more subtle and accurate representation. Their main concern is with the risk of ‘absolute truth’, as

“[…] a photorealistic image […] suggests that detailed information has been
amassed about the objects being shown. Such images […] lead(s) viewers to the conclusion that the information is correct and contains a high degree of certainty and accuracy.” – Strothotte et al. (1999 p.1).

 

Differences

I have already discussed the issues of accuracy and the representation of uncertainty, so I will not delve into this subject at this point. It is however important to note that realistic and functional researchers are coming from two very distinct starting points. Realistic modelers tend to focus on the user experience. The reconstructions are designed for presentation, and the more visually stunning the result is, the more the users will feel involved with it. It is a path which leads to ‘presence’, haptic sheds and interactive models.

Frieman and Gillings (2007) analyse how people ‘perceive’ 3D reconstructions and virtual environments. Not only do they advocate for more realistic experiences, but they believe that this experience must encapsulate all senses.

“Instead, we have argued that, rather than analyse how space is viewed, we should fold vision back into the mix of the sensorium and focus instead on how space is perceived.” – Frieman and Gillings (2007 p.9).

Functional modelers are interested in the interpretation of archaeological data. In the words of van Dam et al:

“Scientific visualization isn’t an end in itself, but a component of many scientific tasks that typically involve some combination of interpretation and manipulation of scientific data and/or models. To aid understanding, the scientist visualizes the data to look for patterns, features, relationships, anomalies, and the like. Visualization should be thought of as task driven […]” – van Dam et al. (2000 p.27).

Although 3D Reconstructions are a visual means of presenting data, this does not mean they are an end product. They have the potential to be used to interpret, and as such they need to be simplified and abstract:

“In order to communicate […] complex information effectively, some form of visual abstraction is required.” – Winkerbach and Salesin (1994 p.1).

Functional modeling is ideal for the exchange of information, as too much detail can distract from the primary focus of the model. For presentation to the public, non-photorealistic models are not as involving, but they can be purposed to explain certain elements, and are especially important for the presentation of uncertainty (Winkerbach and Salesin 1994; Lansdown and Schofield 1995).

 

Intermediate models

Some authors approach the question differently, reaching conclusions that draw from both sides of the argument. One of the most interesting articles on this topic is Engaging places by Mark Gillings (1997). Gillings uses the term ‘hyperreal’ to describe 3D reconstructions, as for him the models are a separate entity from what they are a representation of, which go beyond the original. His main focus is on engagement. Researchers can strive for authenticity, but they will never be able to replicate the same conditions perfectly. No amount of detail inputted can accurately record the shape of every stone or the lighting of a room. Gillings however suggests that this is not even necessary, as the model’s ‘experiental depth’ is of higher importance.

Lansdown and Schofield (1995) emphasise the subjective nature of Visualisation, describing how even photographs are subjective. The way the position of the camera, the single-moment recording and the limitations of the frame mean the photographer has substantial input on the image. Similarly, even the most accurate of models are still based on subjective observations and the way they are presented cannot be objective or ‘perfect’.

 

Conclusion

Personally, I believe the division between realistic and functional models is unnecessary, as they deal with completely separate issues and are not truly in conflict with one another provided we adopt a thoughtful methodology. If the aims of the project are clear and the research thorough, then the models can assimilate aspects of either ideology. With regards to presentation, if the reconstruction’s aim is to explain or investigate specific elements, then a non-photorealistic model will provide a much better basis for research. If instead the project is used to create an emotional response from the user, photorealism will be more successful.

 

References:

Addison, A. C. (2000). Emerging Trends in Virtual Heritage. IEEE Multimedia Vol.7 No.2 pp.22-25.

Burton, N. R., Hitchen, M. E. and Bryan, P.G. (1997). Virtual Stonehenge: a fall from disgrace? Proceedings of CAA 97 pp.16-21.

Chalmers, A. (2002). Very realistic graphics for visualising archaeological site reconstruction. Proceedings of the 18th Spring Conference on Computer Graphics pp. 7-12.

Chalmers, A. and DeBattista, K. (2009). Level of realism for serious games. 2009 Conference in Games and Virtual Worlds for Serious Applications pp.225-232.

Collins, B., Williams, D., Haak, R., Trux, M., Herz, H., Genevriez, L., Nicot, P., Brault, P., Coyere, X., Krause, B., Kluckow, J. and Paffenholz, A. (1993). The Dresden Frauenkirche – rebuilding the past.  In Wilcock, J. and Lockyear, K. Computer Applications and Quantitative Methods in Archaeology Oxford pp.19-24.

Devlin, K. and Chalmers, A. (2001). Realistic visualisation of the Pompeii frescoes. Proceedings of the 1st International Conference on Computer Graphics, Virtual Reality and Visualisation pp.43-48.

Fletcher, M. and Spicer, D. (1992). The display and analysis of ridge-and-furrow from topographically surveyed data. In: Reilly, P. and Rahtz, S. Archaeology in the Information Age pp.59-76.

Frieman, C. and Gillings, M. (2007). Seeing is perceiving? World Archaeology. Vol.39 No.1. Viewing space pp.4-16.

Gillings, M. (1997). Engaging Place: a Framework for the Integration and Realisation of Virtual-Reality Approaches in Archaeology. In: Dingwall, L., Exon, S., Gaffney, V., Laflin, S. and van Leusen, M. Archaeology in the Age of the Internet.

Gutierrez, D., Sundstedt, V., Gomez, F. and Chalmers, A. (2006). Dust and light: predictive virtual archaeology. Journal of Cultural Heritage 8 pp.209-214.

Lansdown, J. and Schofield, S. (1995). Expressive Rendering: A Review of Nonphotorealistic Techniques. IEEE Computer Graphics and Applications pp.29-37.

Miller, P. and Richards, J. (1995). The Good, the Bad, and the Downright Misleading: Archaeological Adoption of Computer Visualisation. In: Huggett, J. and Ryan, N. Computer Applications and Quantitative Methods in Archaeology. Oxford: Tempus Reparatum pp.19-22.

Novitski, B. J. (1998). Reconstructing lost architecture. Computer Graphics World Vol.21 No.2.

Pang, A. T., Wittenbrink, C. M. and Lodha, S. K. (1997). Approaches to uncertainty visualisation. The Visual Computer pp.370-390.

Roberts, J. C. and Ryan, N. (1997). Alternative Archaeological Representations within Virtual Worlds. In: Brown, R. 4th UK Virtual Reality Specialist Interest Group Conference – Brunel University pp.182-196.

Salisbury, M. P., Anderson, S. E., Barzel, R. and Salesin, D. H. (1994). Interactive pen-and-ink illustration. Proceedings of the 21st Annual Conference on Computer Graphics and Interactive Techniques pp.101-108.

Strothotte, T., Masuch, M. and Isenberg, T. (1999). Visualizing Knowledge about Virtual Reconstructions of Ancient Architecture. Computer Graphics International.

Van Dam, A., Forsberg, A. S., Laidlaw, D. H., LaViola, J. J., and Simpson, R. M. (2000). Immersive VR for Scientific Visualisation: A Progress Report. Computer Graphics and Applications Vol.20 No.6 pp.26-52.

Winkenbach, G. and Salesin, D., H. (1994). Computer-generated pen-and-ink illustration. Proceedings of the 21st Annual Conference on Computer Graphics and Interactive Techniques pp.91-100.

Worthing, D. and Counsell, J. (1999). Issues arising from computer-based recording of heritage sites. Structural Survey Vol.17 No.4 pp.200-210.

A Unity 3D script for displaying uncertainty in 3D Reconstructions.

Following up from my latest post, I wanted to share with you one of the solutions I used as part of my MPhil project.

As discussed, a real problem with 3D Reconstruction in archaeology is the subjectivity of the modelling process. While Photogrammetry and Laser Scanning record archaeological features as they are, reconstructions rely on information that is more or less inaccurate. Strothotte et al. (1999) pointed out that uncertainty in Visualisation is caused by imprecision and incompleteness. Site reports tend to present a limited range of data, usually in a 2D format that may not translate to 3D which causes imprecision (Worthing and Counsell 1999). And while interpretation of a site can be built on incomplete information, 3D Reconstruction requires answers to very specific questions that rarely can be answered by the archaeological evidence.

In a bid to display this uncertainty, projects have displayed the model entirely using wireframes or point clouds (Richards 1998). I propose a similar solution: by using a Unity 3D script heavily based on work by Naojitaniguchi (2015), we have different toggles to switch between fully rendered, wireframe and removed. The most uncertain elements are tagged for removal, leaving the more accurate features intact.

Within the scene, the wireframe looks like so:

wireframe

Wireframe 2Wireframe

The Player script initiates the script by attaching it to the objects targeted for removal upon the input of a button:

void RemoveArchaeology(){
		if (Input.GetAxisRaw ("Remove") != 0 && archaeologyRemoved == 0 &&
			removeAxisInUse == false) {
			archaeologyRemoved = 1;
			removeAxisInUse = true;

			foreach (GameObject go in gameObjectArray) {

				go.gameObject.AddComponent ();
			}
		} else if (Input.GetAxisRaw ("Remove") != 0 && archaeologyRemoved == 1 &&
			removeAxisInUse == false) {
			archaeologyRemoved = 2;
			removeAxisInUse = true;

			foreach (GameObject go in gameObjectArray) {

				VertexRenderer vertexRenderer = go.GetComponent ();
				vertexRenderer.RevertToStart ();
				Destroy (vertexRenderer);
				go.SetActive (false);
			}
		}	else if (Input.GetAxisRaw ("Remove") != 0 && archaeologyRemoved == 2 &&
			removeAxisInUse == false){
			archaeologyRemoved = 0;
			removeAxisInUse = true;

			foreach (GameObject go in gameObjectArray) {
				go.SetActive (true);
			}
		}

		if (Input.GetAxisRaw ("Remove") == 0){
			removeAxisInUse = false;
		}
	}

Then, the VertexRenderer script replaces the model with lines:

using UnityEngine;
using System.Collections;

		//Code written by R. P. Barratt
		//robbarratt1@outlook.com
		//
		//Heavily based on a script by Naojitaniguchi (2015).

		//Renders the selected elements as lines.

public class VertexRenderer : MonoBehaviour {

	public Color lineColor;
	public Color backgroundColor;

	private Vector3[] lines;
	private ArrayList linesArray;
	private Material lineMaterial;
	private MeshRenderer meshRenderer;
	private Material initialMaterial;

	public void Start () {

		//Finds the components.
		GetComponent<Renderer> ().enabled = false;
		meshRenderer = GetComponent<MeshRenderer> ();
		if (!meshRenderer) {
			meshRenderer = gameObject.AddComponent<MeshRenderer> ();
		}

		//Saves the initial material.
		SaveInfo ();

		//Finds the line material and sets it.
		Shader shader1 = Shader.Find ("Lines/Background");
		meshRenderer.material = new Material (shader1);
		Shader shader2 = Shader.Find ("Lines/Colored Blended");
		lineMaterial = new Material (shader2);
		lineMaterial.hideFlags = HideFlags.HideAndDontSave;
		lineMaterial.shader.hideFlags = HideFlags.HideAndDontSave; 

		//Creates a list of lines based on the mesh.
		linesArray = new ArrayList ();
		MeshFilter filter = GetComponent<MeshFilter> ();
		Mesh mesh = filter.sharedMesh;
		Vector3[] vertices = mesh.vertices;
		int[] triangles = mesh.triangles; 

		for (int i = 0; i < triangles.Length / 3; i++) {
			linesArray.Add (vertices [triangles [i * 3]]);
			linesArray.Add (vertices [triangles [i * 3 + 1]]);
			linesArray.Add (vertices [triangles [i * 3 + 2]]);
		} 

		lines = new Vector3[triangles.Length];
		for (int i = 0; i < triangles.Length; i++) {
			lines [i] = (Vector3)linesArray [i];
		}

		//Sets material.
		meshRenderer.sharedMaterial.color = backgroundColor;
		lineMaterial.SetPass (0);
	}

	public void OnRenderObject(){

		//Draws lines based on mesh.
		GL.PushMatrix ();
		GL.MultMatrix (transform.localToWorldMatrix);
		GL.Begin (GL.LINES);
		GL.Color (lineColor); 

		for (int i = 0; i < lines.Length / 3; i++) {
			GL.Vertex (lines [i * 3]);
			GL.Vertex (lines [i * 3 + 1]); 

			GL.Vertex (lines [i * 3 + 1]);
			GL.Vertex (lines [i * 3 + 2]); 

			GL.Vertex (lines [i * 3 + 2]);
			GL.Vertex (lines [i * 3]);
		} 

		GL.End ();
		GL.PopMatrix ();
	}

	void SaveInfo(){

		//Saves initial material.
		initialMaterial = meshRenderer.material;
	}

	public void RevertToStart(){

		//Returns to initial material.
		GetComponent<Renderer> ().enabled = true;
		meshRenderer.material = initialMaterial;
	}
}

The script requires Unity3D to run at the moment, but I am sure it can be adapted for other platforms.

The reason for this script is to allow users to choose different options, displaying the finished model with a more realistic skin but also allowing for a more accurate representation.

References:

Naojitaniguchi (2015). WireFrame. Available: https://gist.github.com/naojitaniguchi/862724c55bd322695511. Last accessed 20th Oct 2017.

Richards, J. D. (1998). Recent Trends in Computer Applications in Archaeology. Journal of Archaeological Research Vol.6 No.4 pp.331-382.

Strothotte, T., Masuch, M. and Isenberg, T. (1999). Visualizing Knowledge about Virtual Reconstructions of Ancient Architecture. Computer Graphics International.

Worthing, D. and Counsell, J. (1999). Issues arising from computer-based recording of heritage sites. Structural Survey Vol.17 No.4 pp.200-210.