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8/3/2019 Final Paper 3D Techniques
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Dimitrios Tzanakis
Yannis Psaromiligkos
Daune West
3D Techniques andTools for Preservation
and Visualization ofCultural Heritage
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Contents
Introduction
Research Problem
Presentation of the state of the art
Case study
Conclusions
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Introduction
Cultural heritage is priceless
Cultural heritage preservation and
documentation is essential
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Problems
Cultural heritage objects are spreadaround the world
Cultural heritage sites and monuments arealways in jeopardy (pollution, rain, sun,wind, fire, earthquakes, war actions)
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3D digitization and visualisation
of cultural heritage benefits
Restoration study
Model study
Digital 3D models creation
Model data base development of similar
objects
Virtual museums
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Research Problem
What are the main techniques and tools inorder to:
model and visualize cultural heritage objectsdigitally with the use of InformationTechnology according to the context ofcultural heritage documentation andvisualisation
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Presentation of the state of the art
3D laser scanning techniques
Photogrammetry techniques
Visual description of 3D objects
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Main 3D laser scanning
techniques
Time of flight of a laser pulse
This methodology is also known as LightDetection And Ranging (LIDAR).
Laser Triangulation
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A laser pulse is emitted tothe object
The distance between the signalsending device and the surface ofthe object is calculated from therequired time between transmission
and reception of the laser pulse.
Time of flight of a laser pulseor Light Detection And Ranging (LIDAR)
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A CCD sensor using the high optical definition of a laser beam,that is projected on the under study object, and via triangulation
equations, calculates the position of each point that isilluminated by the laser beam in the 3D space.
Laser Triangulation
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laser scanning techniques
(+) More reliable and more usable by nonexperts in many projects
(-) Require many man hours
(-) Expensive
Suitable for large scale cultural heritage
surveying projects => high accuracyproducts with significant efficiency.
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Main photogrammetric
techniques
Stereophotogrammetry
Convergent or non-stereoscopicphotogrammetry
Structure from motion
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Stereophotogrammetry
Axes of camera should be parallel in twoconsequent shooting positions and vertical tothe surface of the under study object
Photogrammetric triangulation
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Convergent photogrammetry
The camera axes converge toward thegravity centre of the object
Marked Feature Points (a, b, c)
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Structure from motion
Automatic calculation of the orientationfrom marker-less photos.
Un-ordered photo sequences can be used
for input
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Photogrammetry techniques
(+) Ideal for cultural heritage objectswithout complex shapes
(+) Ideal when money, location andtime constraints exist
(+) Much more flexible in the case ofmulti dimensions projects than laserscanning techniques
(-) Experienced operators
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Visual description of 3D objects
Point Cloud
Each pointcorresponds to afeature point andembeds 3Dcoordinates
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Triangular mesh is used in most 3Dimaging applications
Provides much more visual information
than the point cloud
Teapot wireframe rendered teapot
Visual description of 3D objects
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Case study
Photogrammetric techniques selection
evaluation:
More appropriate for the case studyaccording to time, money and other
constraints
Essentially fulfil this case studysscope for visualisation and virtual
reality as well as its requirements
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Software tools
Arc3D Webservice
MeshLab
PixMaker Pro
Equipments A tripod
Two consumer photo cameras
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The Cultural Heritage object
Saint Tryfonas Orthodox Church,
Eleonas, Peloponnese
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ARC 3D Webservice
The 3D models were created by the ARC3D Webservice, developed by the VISICS
research group of the KatholiekeUniversiteit Leuven in Belgium
The uploading procedure required manyattempts and time to achieve usable
results Open source
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MeshLab
Developed by Visual Computing Lab of theInstitute of Information Science andTechnologies of the Italian National
Research Council CNR-ISTI in Italy 3D triangular mesh processing tool
Provides functions for cleaning, editing,
simplifying, remeshing, measuring,merging, visualising, converting, etc.
Open source
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MeshLab
(+) Can import meshes (models) in manyformats and export the results in almost allknown formats
(-) Not so stable, has no undo function andneeds great computer processing power
(-) Significant training time
(-) No complete manual (-) A lot of man hours to process the sub
scenes meshes and align and merge them
into the final model
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Case study
The procedure
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In order to create a 360o model, one mustdivide the 360o scene into individual sub
scenes
ARC 3D is not able to provide 3D data for
model creation that encircles an object
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The upload tool enables the user to beconnected to the Webservice and after
authentication to upload a selected sequence ofphotos to Arc3D server.
Users
can uploadunordered
and marker-less photos.
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ARC 3D Webservice
Automatic procedure in the server side
Parallel processes running on a cluster of
Linux personal computers
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The results:
camera parameters,
range-dense depthmaps (i.e. pointclouds), texture andquality maps forevery photo
Arc 3D Webservicecalculates the 3D data
and camera parame-
ters for each photo
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The 3D models were post processed byMeshLabs Arc3D import interface.
Main post processing functions: subsampling,
cleaning,
noise filtering, hole filling and merging.
MeshLab
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The four 3D partial models were importedand cleaned in MeshLab
They are all loaded into the same newMeshLab project and while they hadoriginally positioned in different reference
spaces
MeshLab
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they were rototranslated in
order to be placed into the same
single reference space and finallyto be aligned and merged.
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Snapshots of the VRML model
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ResolutionSize
(uncompressed)
Size(compressed
with gzip)
Full resolution 100% 137,594 Kb 31,735
High resolution 64% 87,431 Kb 20,628
Medium resolution 25% 34,463 kb 8,298
Low resolution 13% 17,977 kb 4,405
Three different model versions of reduced
resolutions (decimated and compressed) Fast download time for users with slowconnections rates
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3D model high resolution (64%)
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Case study - Vitrual tour section
PixMaker Pro
Virtual tour Use of Java
www.stvtour.comule.com
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Case study conclusions
Photogrammetry techniques: low cost
medium training requirements
medium post processing time
sufficient accuracy models with hightexture quality
no need for laboratory conditions
fast data acquisition and multi dimensionobjects compatibility
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Case study conclusions
Structure from motion technique suitable for:
virtual reality applications andvisualisation purposes (although not
highly accurate nor stable enough)
provision of 3D models from un-orderedand marker-less photos
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Final Conclusions In many methodologies their evolution is
proportional to IT evolution
In 3D digitization techniques the storage,
processing, archiving, management andvisualisation of the acquired digital data canonly be realized by IT utilization
Modern IT technologies (e.g. Web, VirtualReality) offer easy access to cultural heritage
=> The contribution of IT in cultural heritagedocumentation is crucial:
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Final Conclusions
Nowadays there is no all-in-one culturalheritage objects documentation solution
The combination of different techniques inorder to achieve the matching of theiradvantages, a hybrid technique, may leadto a complete solution
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Final Conclusions
The most crucial limitation of photo-grammetric techniques is the software
If the development of IT and softwarecontinues its current pace, it will be
possible in the near future forphotogrammetry to overcome its basic
limitations providing the panacea incultural heritage documentation
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The future of cultural heritagepreservation and
documentation belongs to
Photogrammetry !
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Questions