DH101 2013/2014 course 4 - Digitization techniques 2D and 3D

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DH101 2013/2014 course 4 - Digitization techniques 2D and 3D

  1. 1. Digital Humanities 101 - 2013/2014 - Course 4 Digital Humanities Laboratory Frederic Kaplan frederic.kaplan@epfl.ch
  2. 2. o About 400 persons per day on dh101.ch Digital Humanities 101 - 2013/2014 - Course 4 | 2013 2
  3. 3. o The first Venice Digital Humanities Fall School http://digitalvenice.wordpress.com/ Digital Humanities 101 - 2013/2014 - Course 4 | 2013 3
  4. 4. o Semester 1 : Content of each course • 19.09 Introduction to the course / Live Tweeting and Collective note taking • 25.09 Introduction to Digital Humanities / Wordpress / First assignment • 2.10 Introduction to the Venice Time Machine project / Zotero • 9.10 No course • 16.10 Digitization techniques / Deadline first assignment • 23.10 Transcription / XML / Presentation of projects • 30.10 Pattern recognition / OCR / Deadline peer-reviewing of first assignment Digital Humanities 101 - 2013/2014 - Course 4 | 2013 4
  5. 5. o Semester 1 : Content of each course • 6.11 Semantic modelling / RDF • 13.11 Historical Geographical Information Systems / Deadline Project selection • 20.11 Procedural modelling / City Engine • 27.11 Crowdsourcing / Wikipedia • 4.12 Group work on the projects • 11.12 New narrations and museographic experiences / Deadline Projet blog • 18.12 Oral exam / Presentation of projects Digital Humanities 101 - 2013/2014 - Course 4 | 2013 5
  6. 6. o Structure of today's course • 2d Imaging techniques • 3d Imaging techniques • Lot’s of material to cover but as we go, many videos and demonstrations. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 6
  7. 7. o Thanks to Sabine Susstrunk for some of the material presented in the next slides. Check her research : http://ivrg.epfl.ch/people/susstrunk Digital Humanities 101 - 2013/2014 - Course 4 | 2013 7
  8. 8. o Image archives contain different kinds of digital images Digital Humanities 101 - 2013/2014 - Course 4 | 2013 8
  9. 9. o Images in image archives • They are different kinds of images in an image archive. • Images either represent digital reproduction of documents (surrogate) or are original digital documents Digital Humanities 101 - 2013/2014 - Course 4 | 2013 9
  10. 10. o Processes that produce digital images • Capturing images : From analog to digital • Preserving images : Format conversion • Displaying images : On-the-fly production of images for display Digital Humanities 101 - 2013/2014 - Course 4 | 2013 10
  11. 11. o Different usages of digital images • Visual reference (low quality) • Print reproduction • Replacement of the original • An image database typically contain one or more representations (master/derivative files) • The Master image is the best quality file in the archive. The Derivative image is optimised for a specific purpose (Thumbnails, Screen reproduction, Print reproduction) Digital Humanities 101 - 2013/2014 - Course 4 | 2013 11
  12. 12. o Digital images are produced by algorithms Digital Humanities 101 - 2013/2014 - Course 4 | 2013 12
  13. 13. o Sensors • Type of sensors : CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) • Photosensitive material : Silicon (semiconductor) • Arrangement of photo cells in rows (linear arrays) and areas (area array) Digital Humanities 101 - 2013/2014 - Course 4 | 2013 13
  14. 14. o A complex process • A colour image is the result of a complex algorithm and a particular hardware • The resolution depends largely on the optics of the capturing system (diffraction, lens aberrations) and only partly on the mega-pixels. • An digital image is difficult to interpret if the information about the software and hardware used are not provided. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 14
  15. 15. o Many types of scanners exist Digital Humanities 101 - 2013/2014 - Course 4 | 2013 15
  16. 16. o Drum scanners Digital Humanities 101 - 2013/2014 - Course 4 | 2013 16
  17. 17. o ILinear arrays Digital Humanities 101 - 2013/2014 - Course 4 | 2013 17
  18. 18. o Cameras • Cameras with colour filters for visible light • Multispectral cameras • Material absorption / reflectance is mostly wavelength dependent • Imaging beyond the visible spectrum allow for surface imaging (ultra-violet) and subsurface imaging (near and middle/far infrared) Digital Humanities 101 - 2013/2014 - Course 4 | 2013 18
  19. 19. o Multi-spectral Imaging of the Mona Lisa : http://www.dailymotion.com/video/k3GIpau9WkVvazepCB Digital Humanities 101 - 2013/2014 - Course 4 | 2013 19
  20. 20. o Capturing methods • You can build (almost) any capturing technology into almost any device Digital Humanities 101 - 2013/2014 - Course 4 | 2013 20
  21. 21. o Fastest book scanner in the world : http://youtu.be/ExW64zOZGoI Digital Humanities 101 - 2013/2014 - Course 4 | 2013 21
  22. 22. o X-ray microtomography • Research conducted at EPFL by Prof. Margaritando. • Based on the advanced characteristics of synchrotron sources, x-ray microtomography radically transformed the scope of standard radiology and tomography, bringing the spatial resolution for hard-x-rays to the record level of 15 nm and the time resolution to less than 1 ms per projection image. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 22
  23. 23. o X-ray microtomography • Computer reconstruction of tomography image sets yields all sorts of three dimensional views and navigation movies inside the specimens. • This suggests the possibility of reading ancient documents without even opening or unrolling them. • The procedure would be fully non-invasive, fast and with a minimal level of risk. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 23
  24. 24. o X-ray microtomography • The practical testing and implementation requires a targeted effort to solve a number of problems and to realize a field implementation right where the patrimony is located i.e., without a synchrotron source. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 24
  25. 25. o Formats Digital Humanities 101 - 2013/2014 - Course 4 | 2013 25
  26. 26. o Compression • No compression is appropriate for all master files and files that will be re-processed extensively. • Lossless compression (LZW, JPEG2000). Same as above. The size of the file is usually around 0.5 to 0.7 of the uncompressed file size • Lossy compression (JPEG, JPEG2000, GIF, PNG) : Derivative encoding for storage and transmission. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 26
  27. 27. o File formats • For master files, the file format should be a standard. • TIFF, EXIF, JPX(JPEG2000) are standard file formats. • Derivative files can be encoded depending on the application Digital Humanities 101 - 2013/2014 - Course 4 | 2013 27
  28. 28. o Metadata • Image metadata (camera and scene parameter) facilate rendering a sensor encoded image to an output-referred image. TIFF, EXIF, JPX have defined mandatory and optional tags. • Metadata tags are also used to store copyright information • Image metadata should always be stored with the image file. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 28
  29. 29. o 3d digitization techniques Digital Humanities 101 - 2013/2014 - Course 4 | 2013 29
  30. 30. o Demo 123DCatch Digital Humanities 101 - 2013/2014 - Course 4 | 2013 30
  31. 31. o Thanks to Roberto Scopigno for some of the material presented in the next slides. Check his research http://http://vcg.isti.cnr.it/~scopigno/ Digital Humanities 101 - 2013/2014 - Course 4 | 2013 31
  32. 32. o Families of 3d digitization techniques • 2D image-based rendering (panoramic images, RTI images) • Standard CAD modelling (manual process) • Approaches based on Sampling • 3d scanning (active) • 3d from images (passive) Digital Humanities 101 - 2013/2014 - Course 4 | 2013 32
  33. 33. o 2D image-based rendering : Panoramic images • Some image-based rendering are interesting for some applications • If you don’t have to move in your model, panoramic images can be enough. • Ex : Cluny Augmented Reality System : http://www.youtube.com/watch?v=Z-EwXWjU0nw Digital Humanities 101 - 2013/2014 - Course 4 | 2013 33
  34. 34. o 2D image-based rendering : RTI • RTI stands for Reflection Transmission Images. his is done by putting your camera on a tripod by taking several images and regularly changing the light. • Sometimes a dome is used http://vimeo.com/67164689 • With such images, you cannot change the view, but change the way your image reflects light. For instance, you can move a virtual light and see how it affects your image. • Ex : RTI example : papyrus fragment from Cultural Heritage Imaging : http://vimeo.com/33245119 Digital Humanities 101 - 2013/2014 - Course 4 | 2013 34
  35. 35. o Modelling approaches and sampling approaches Digital Humanities 101 - 2013/2014 - Course 4 | 2013 35
  36. 36. o Modelling approaches and sampling approaches • There are big differences in terms of approaches between modelling approaches and sampling approaches. • Modelling implies redrawing. Before photography, painters where making drawings of other painters painting. With the arrival of photography one could start sampling the painting. • The same olds for 3d models. You have wonderful technology developed for the movie market that permits to produce great 3d models. The 3D model is usually complete. On the contrary, sampling/scanning approaches the 3D model, accuracy is known is usually uncompleted (many unstapled regions). If you want to communicate, 3D models are great, if you want to study a building, sampling is interesting. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 36
  37. 37. o 3d scanning devices • There are different 3d scanning devices. • They use active optical technologies. You need for instance a laser and a camera. • The regions that are not seen by the two devices cause problem in the restitution. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 37
  38. 38. o 3d scanning devices : Triangulation • Triangulation is an old an simple approach (Thales) • Such systems are good for small/medium scale artefacts (e.g. statues). They permit to reach high accuracy (0.05 mm) and a very dense sampling, very rapidly (300 000 points / s) Digital Humanities 101 - 2013/2014 - Course 4 | 2013 38
  39. 39. o 3d scanning devices : Time of Flight techniques • Time of Flight techniques measure the time a light impulse needs to travel form the emitter to the target point. • A source emits a light pulse and starts a nanosecond watch. • With Time of flight techniques, one can do large scale models (architectures). This can work in wide workspace, but accuracy is smaller. This because sound is too slow and light is too fast. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 39
  40. 40. o Kinect • Kinect is of less good quality than these techniques. But it has a better framerate. • If you have application where the dynamic acquisition is important. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 40
  41. 41. o Digital Humanities 101 - 2013/2014 - Course 4 | 2013 41
  42. 42. o Digital Humanities 101 - 2013/2014 - Course 4 | 2013 42
  43. 43. o Material extracted from • http://www.iuav.it/SISTEMA-DE/Laboratori2/laboratori/ pubblicazi/2011_asita-Canal-Grande.pdf • http://www.iuav.it/SISTEMA-DE/Laboratori2/laboratori/ pubblicazi/2008_laser-scanner.pdf • http://www.iuav.it/SISTEMA-DE/Laboratori2/laboratori/ pubblicazi/2012-Archeomatica.pdf Digital Humanities 101 - 2013/2014 - Course 4 | 2013 43
  44. 44. o 3d scanning pipeline • Planning (where are you going to put your scanners) • Acquisition • Editing (removing people, etc.) • Registration (aligning coordinate systems of different scans, 4 points are enough) • Merging (Based on a set of range map, a single surface is computed, this is typically done by another software using for instance Poisson surface reconstruction), • Simplification (for using on a webpage or for 3d printing), texturing. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 44
  45. 45. o Merging • In some sense, merging is destroying the data, creating an medium shape. • Actually, some architects prefer to use point clouds directly obtained based on sampling. • But it is also a way of improving the accuracy of the model, removing the noise thought this smoothing process. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 45
  46. 46. o Multiresolution encoding • Multiresolution encoding can be build on top of simplification technology. • The goal is to structure the data to allow to extract from the model (in real time) an optimal representation for the current view (view dependent models produced on the fly). • This is particularly interesting if you are rendering terrains. Mesh is more and more coarse as we get farther from viewpoint. Zones which are outside the view frustum are very coarse. • For multiresolution encoding, you have to keep all the intermediate levels of simplification. Some de facto standards exist for terrain (used in Google Earth). For object there is no de facto standard. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 46
  47. 47. o Assisted modelling Digital Humanities 101 - 2013/2014 - Course 4 | 2013 47
  48. 48. o SketchUp • You can start with a single image and use SketchUp (http://sketchup.com) • If this image permits to extract the main lines of perspective you can model rapidly the 3d shape of an object. • You need to find some features of the object that permits to have two axis (ideally orthogonal). • You draw the two vanishing lines. • Partial calibration with only a single photo is sufficient provided only the axis can be recovered. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 48
  49. 49. o Demo Sketchup Digital Humanities 101 - 2013/2014 - Course 4 | 2013 49
  50. 50. o Photogrammetry • For photogrammetry you need several images and click on points which are common to the different images. • These points permits to estimate the camera position for the different images. • For simple geometry you can get very good reconstruction in very short time. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 50
  51. 51. o Multi-view stereo matching algorithms • In the recent years a new class of algorithms has tried to completely automatised these processes. These are multi-view stereo matching algorithms. • In some sense the approach is the inverse of assisted learning. You can have a very large number of point (with a lot of errors). You remove the errors and wait to have a good number of points. • You need to take pictures close to one another, so that the computer can match them easily. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 51
  52. 52. o One interesting example of the use of such algorithms is the Photo Tourism project using photo by tourists (phototour.cs.washington.edu/). Digital Humanities 101 - 2013/2014 - Course 4 | 2013 52
  53. 53. o Demo 123DCatch Digital Humanities 101 - 2013/2014 - Course 4 | 2013 53
  54. 54. o Sketchup vs 123DCatch ? Digital Humanities 101 - 2013/2014 - Course 4 | 2013 54
  55. 55. o Sketchup vs 123DCatch ? • For multi-view stereo matching algorithms to work you need many features on the objects. • Assisted modelling approach using for instance SketchUp can work for non textured objects. Digital Humanities 101 - 2013/2014 - Course 4 | 2013 55
  56. 56. o What we have not covered • 3d Printing • Documenting the material Digital Humanities 101 - 2013/2014 - Course 4 | 2013 56

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