3D Sensing for 3D Printing:
(because CAD is hard)
Nick Armstrong-Crews
July 24, 2014
Who am I?
• Current: Roboticist, MIT Lincoln Laboratory
– Focus: 3D perception
• Past: Carnegie Mellon Robotics Institute
– Focus: Planning under uncertainty
• Future: Heuristic Labs
– Focus: 3D sensors
• Origin (fun fact): Alaska
– Focus: None
3D Printer Meetup - 2
NAC 7/24/14
“Nick Armstrong-Crews” - http://www.linkedin.com/in/nickarmstrongcrews
Why 3D Sensing is Important
• Theme: CAD is hard; a barrier to 3D printing revolution
– Imagination ---(CAD)---> digital model ---(3D printing)---> Reality
– Harder than 2D (i.e., photo-realistic painting/sketching)
“This stuff is really hard. It's hard to learn,
hard to use, and mistakes have real
consequences. This [is true] of any CAD or
modeling software.”
• Aside: 2D sensing sucks
– Loss of depth information; loss of absolute dimensions
– Simply insufficient to aid creation in a 3D world
• Solution: 3D sensing to the rescue!
• Caveat: 3D sensing can be noisy
– But fixing up a 3D model is easier than creating!
3D Printer Meetup - 3
NAC 7/24/14
“CAD is Hard” - http://sliptonic.com/cad-is-hard/
The “Matter Remixer”
3D Printer Meetup - 4
NAC 7/24/14
“Reality Remixing” - http://bit.ly/MatterRemixerKS
3D Sensing Techniques
• Principles:
𝒃
– Time-of-flight: 𝒅 = 𝒄𝒕 𝟐 , 𝜺𝒅 ~𝜺𝒕
– Stereo parallax (triangulation): 𝒅 = 𝒃𝒇 ∆𝒖 , 𝜺𝒅 ~𝒅𝟐
– Multi-view stitching (mapping, SLAM): (complicated)
• Implementations:
– Passive stereo vision:
like humans! two cams, rigid mount, sparse and not robust
and reliant on background texture
– Structure-from-motion: monocular, move camera over time
– LIDAR: raster scanning/spinning point detector
– Active stereo vision: create own perfectly structured light
3D Printer Meetup - 5
NAC 7/24/14
“Time-of-Flight Camera – An Introduction” - http://www.ti.com/lit/wp/sloa190b/sloa190b.pdf
“Triangulation (computer vision)” - http://en.wikipedia.org/wiki/Triangulation_(computer_vision)
“Projected Texture Stereo” - http://www.willowgarage.com/sites/default/files/ptext.pdf
“Serveo w/ Planar LIDAR” - http://april.eecs.umich.edu/magic/about/
Available Hardware Comparison
Principle
Cost
Resolution
DepthSense
ToF
$299
640x480, +-3cm
at 3m
kinda
Kinect
(Xbox One)
ToF
$399
520x240
kinda
Xtion / Kinect
(original)
ToF
$99-$150
640x480, +-2cm
at 2m
PrimeSense
inside
Cubify Sense
Active
Stereo
$399
640x480, +-2cm
at 2m
PrimeSense
inside
Occipital
Structure
Active
Stereo
$379
640x480, +-2cm
at 2m
Yes
(tablet)
Apple-only,
PrimeSense
inside
Google Project
Tango
Active
Stereo
$1024
640x480, +-2cm
at 2m
Yes
(tablet/phone)
Limited
release, preproduction
HL
LazeeEye
Active
Stereo
$75
3D Printer Meetup - 6
NAC 7/24/14
“LazeeEye: Turn your Smartphone into a 3D Camera” - http://kck.st/1gVCcrB
Mobile?
Yes
(phone)
Outdoors?
Yes
Caveats
Windoze 8.1
Pre-production
Useful Resources
• Structure-from-Motion
– AutoDesk 123D Catch - http://www.123dapp.com/catch
– VisualSfM - http://ccwu.me/vsfm
– Seene iPhone App - http://seene.co
• DIY
– DIY Structured Light - http://mesh.brown.edu/byo3d/source.html
– DIY Stereo Cams http://wiki.ros.org/camera_calibration/Tutorials/StereoCalibration
(any cam pair, but recommend PS4 Eye or dual PS3 Eyes)
• Computer-assisted 3D Editing
– Meshlab - http://meshlab.sourceforge.net
– AutoDesk Meshmixer - http://meshmixer.com
3D Printer Meetup - 7
NAC 7/24/14