Mini Course Archaeological Sciences Interdisciplinary Group University of Minnesota 1

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1 Mini Course Archaeological Sciences Interdisciplinary Group University of Minnesota 1

2 Introduction What is photogrammetry, how does it work, what materials does it work on, and how does it compare to other methods of 3D capture? Taking photos for photogrammetry Explanation of photogrammetry rig What camera properties / settings should one use? How should the camera / target object be positioned? How to take photos using the rig 5 minute break? 2

3 Processing photos / models Auto masking in Adobe Photoshop Using Agisoft PhotoScan (standard edition) Model editing using other software (Geomagic and Meshlab) Sharing models Creating 3D PDFs using PhotoScan, Daz 3D and Adobe Acrobat 3

4 General Definition: Taking measurements from photographs. How we re going to talk about it today: A way of creating 3D models by estimating the three dimensional coordinates of points on an object using triangulation. 4

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7 3D models can be used as: As a data source As a presentation tool

8 Objects 8

9 Objects 9

10 Objects 10

11 Objects 11

12 Structures / sites / excavations 12

13 Structures / sites / excavations 13

14 Structures / sites / excavations 14

15 Structures / sites / excavations 15

16 Structures / sites / excavations 16

17 Landscapes 17

18 It s a fairly easy to get started

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20 It s relatively inexpensive 20

21 It s relatively inexpensive 21

22 It s relatively inexpensive 22

23 It s portable 23

24 It does not require an external source of electricity 24

25 It s less likely to break 25

26 It can takes less time to capture object geometry (can be important in the field) 26

27 It in some cases produces better models than other options for certain materials / morphologies, in fewer man hours. 27

28 May not be as precise / accurate as other Can t compare to what you get from a high end scanner Photogrammetry reconstructs geometry rather than measuring it More testing needs to be done to check this quantitatively for different materials / morphologies / scales 28

29 There is no inherent scale 29

30 In PhotoScan standard edition, scale must be added using other software (Geomagic or Meshlab) Accuracy does not appear to be a problem based on initial tests (but I haven t run the numbers yet). 30

31 It doesn t work (well) on all materials / things Shiny / reflective things Things without much surface texture or patterning Transparent / semi transparent things Very small things A lot of these things are also issues with other scanning methods 31

32 Issues due to some material properties may be mitigated by coating objects 32

33 Issues due to some material properties may be mitigated by coating objects 33

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37 Developer spray is obviously not an option for all objects Porous objects / objects that cannot be cleaned safely or easily Objects with potential residues Clear or light colored objects For models where texture is important Developer spray may cause alignment issues due to the pattern of spray not matching 37

38 It doesn t work (well) on all materials / things Shiny / reflective things Things without much surface texture Transparent / semi transparent things Very small things Possible solutions: Spray Polarizing filters / macro lenses? 38

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40 Display / Outreach Data / Collections Sharing Supplementary Material / Visual Aid Analysis / Measurement 40

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48 Goals for my rig: Streamline and systematize the process Doesn t take up much space Mitigates issues with lighting Able to use a background Be portable / durable Be cheap 48

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52 better quality photos = better quality models You are likely to achieve the best results using manual settings on your camera. Differences in model quality between point and shoot and DSLR cameras unclear (more on this later). Ideally, photos should be as large as possible with the highest resolution possible 52

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58 ISO should be set as low as possible. 58

59 ISO should be set as low as possible. 59

60 F stop should be set as high as possible. 60

61 F stop should be set as high as possible. 61

62 F stop should be set as high as possible. 62

63 F stop should be set as high as possible. 63

64 Shutter speed and white balance will depend on the environment and other settings. 64

65 When using a point and shoot, it s usually best to use macro mode. DSLRs can have (auto)focus issues at close range with standard lenses, and may not always be the best option. 65

66 Standard DSLR lenses = have to be further away from the subject, meaning it takes up less of the frame. 66

67 Having less detailed photographic data can result in alignment problems. 67

68 PhotoScan cannot import RAW images With DSLRs, there is more that can go wrong if you don t know what you re doing. 68

69 DSLRs have options point and shoots don t have (macro lenses, higher f stops, polarizing filters, etc.) DSLRs are powerful, and with great power comes great responsibility For most applications, a good point and shoot will probably do just fine. 69

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74 Taking photos summary Take pictures of a label at the start, and of the scale alone half way through Take ~44 photos per side Every 30 degrees level with the object (starting at 0 ) Every 30 degrees with camera elevated (starting at 10 ) Every 30 degrees with camera elevated more (starting at 20 ) About every 45 to 90 degrees (capturing top of object) Rotate object 180 degrees halfway through 74

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76 Processing photos / models Auto masking in Adobe Photoshop Using Agisoft PhotoScan (standard edition) Model editing using other software (Geomagic and Meshlab) Sharing models Creating 3D PDFs using PhotoScan, Daz 3D and Adobe Acrobat Conclusions / further work 76

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79 Steps: Importing photos Importing masks Aligning photos Adjusting alignment Building a dense cloud Editing the dense cloud Aligning chunks Building a mesh Masking out putty Building texture Scaling the mesh Decimating the mesh Exporting the mesh 79

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82 What you can do with 3D PDFs Lighting / texture options Measurement View cross sections Exporting 3D PDFs directly from PhotoScan With and without texture Including multiple models in one file Daz 3D and Adobe Acrobat 82

83 Gil Tostevin John Soderberg Matt Edling Keith Manthie Kristy Golubiewski Davis Jason Massey Marie Soressi Morgan Roussel Andre Morala Glen Favretto Steffen Schatz UMN Anthropology Block Grants UMN Graduate Research Partnership Program Stout Wallace Fellowship Program Leakey Foundation 83