Structured Light + Range Imaging. Lecture #17. (Thanks to Content from Levoy, Rusinkiewicz, Bouguet, Perona, Hendrik Lensch)

Transcription

1 Structured Light + Range Imaging Lecture #17 (Thanks to Content from Levoy, Rusinkiewicz, Bouguet, Perona, Hendrik Lensch)

2 3D Scanning

3 Stereo Triangulation I J Correspondence is hard!

4 Structured Light Triangulation I J Correspondence becomes easier!

5 Structured Light Any spatio-temporal pattern of light projected on a surface (or volume). Cleverly illuminate the scene to extract scene properties (eg., 3D). Avoids problems of 3D estimation in scenes with complex texture/brdfs. Very popular in vision and successful in industrial applications (parts assembly, inspection, etc).

6 Light Stripe Scanning Single Stripe Light plane Source Camera Surface Optical triangulation Project a single stripe of laser light Scan it across the surface of the object This is a very precise version of structured light scanning Good for high resolution 3D, but needs many images and takes time

7 Triangulation Object Light Plane Ax + By + Cz + D = 0 Laser Camera Project laser stripe onto object

8 Triangulation Object Light Plane Ax + By + Cz + D Laser = 0 Image Point ( x', y') Camera Depth from ray-plane triangulation: Intersect camera ray with light plane x y = = x' z / y' z / f f z = Df Ax' + By' + Cf

9 Example: Laser scanner + very accurate < 0.01 mm more than 10sec per scan Cyberware face and head scanner

10 Example: Laser scanner Digital Michelangelo Project

11 3D Model Acquisition Pipeline 3D Scanner

12 3D Model Acquisition Pipeline 3D Scanner View Planning

13 3D Model Acquisition Pipeline 3D Scanner View Planning Alignment

14 3D Model Acquisition Pipeline 3D Scanner View Planning Alignment Merging

15 3D Model Acquisition Pipeline 3D Scanner View Planning Alignment Done? Merging

16 3D Model Acquisition Pipeline 3D Scanner View Planning Alignment Done? Merging Display

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18 Great Buddha of Nara

19 Scanning and Modeling the Cathedral of Saint Pierre, Beauvais, France

20 Portable 3D laser scanner (this one by Minolta)

21 Faster Acquisition? Project multiple stripes simultaneously Correspondence problem: which stripe is which? Common types of patterns: Binary coded light striping Gray/color coded light striping

22 Binary Coding Faster: n 2 1 stripes in n images. Projected over time Example: 3 binary-encoded patterns which allows the measuring surface to be divided in 8 subregions Pattern 3 Pattern 2 Pattern 1

23 Binary Coding Assign each stripe a unique illumination code over time [Posdamer 82] Time Space

24 Binary Coding Example: 7 binary patterns proposed by Posdamer & Altschuler Projected over time Pattern 3 Pattern 2 Codeword of this píxel: identifies the corresponding pattern stripe Pattern 1

25 More complex patterns Works despite complex appearances Works in real-time and on dynamic scenes Need very few images (one or two). But needs a more complex correspondence algorithm Zhang et al

26 Real-Time 3D Model Acquisition

27 Captured video (30H z) Captured video (3000H z) Reconstruction (30H z) Reconstruction Reconstruction different (120Hview z) (120H z)

28 Captured video (30H z) Captured video (3000H z) Reconstruction (30H z) Reconstruction Reconstruction different (120H view z) (120H z)

29 Continuum of Triangulation Methods Multi-stripe Multi-frame Single-stripe Single-frame Slow, robust Fast, fragile

30 Microsoft Kinect IR LED Emitter IR Camera RGB Camera

31 Microsoft Kinect Depth map Speckled IR Pattern

32 3D Acquisition from Shadows Bouguet-Perona, ICCV 98

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39 Fluorescent Immersion Range Scanning

40 Fluorescent Immersion Range Scanning

41 Structured Light Reconstruction Avoid problems due to correspondence Avoid problems due to surface appearance Much more accurate Very popular in industrial settings Reading: Marc Levoy s webpages (Stanford) Katsu Ikeuchi s webpages (U Tokyo) Peter Allen s webpages (Columbia)