• Scan large statues (~5m) at high resolution (1/4 mm)
  • Capture chisel marks
  • Record color/reflectance for re-lighting

• Several challenges
  • Fragile, precious sculptures
  • Bulky equipment
  • Visibility

• Another major challenge: huge data sets!

• Probe object by physical touch
  • Can be highly accurate
  • Even works on transparent objects
  • Often used in manufacturing control
  • Slow scanning, sparse set of samples

• Modeling approach (historic) at Pixar
  • Hand-held contact scanner
  • Allows direct placement of mesh vertices
  • Imprecise and lots of manual work

• Invasive: unsuitable for fragile objects!

• Probe object by laser or infrared light
  • Emit pulse of light and measure the time until the reflection from the surface is “seen” by a detector
  • Speed of light & measured round-trip time ==> distance to surface

• Capturing a full surface
  • Sweep beam over the surface, or
  • Use time-of-flight camera
• High speed of light makes accurate measurement difficult

• Laser LIDAR
  • Light Detection and Ranging
  • Good for long distance scans
  • 6mm accuracy at 50m distance

• Two “cameras” identify the same 3D point
  • Compute depth from angles and baseline

• Two “cameras” identify the same 3D point
  • Compute depth from angles and baseline

• Passive Stereo Matching
  • Find and match features in both images

• With high resolution cameras, skin has a lot of details!

• Passive stereo capturing is fast (just one shot)

• More than two cameras!
• Same triangulation principle: one camera pair at a time.

• 1 camera and 1 projector
  • Project special patterns to identify pixels

• 1 camera and 1 projector
  • Project special patterns to identify pixels

• Consumer-level scanner: e.g. Microsoft Kinect
  • Project infrared pattern, but just one frame
  • Fast (30fps), but noisy data

• Comparison to custom-built scanner (>$10k)

• 1 camera and 1 laser beam
  • Sweep laser, identify laser in camera image

• Laser scanning!

• Common issues with scanned data:
  • Noise (especially bad with structured light scanning)

• Common issues with scanned data:
  • Noise (especially bad with structured light scanning)
  • Holes
    

• Common issues with scanned data:
  • Noise (especially bad with structured light scanning)
  • Holes
  • Insufficient resolution
    

• Scanning is only the beginning!
• Transform acquired samples into triangle mesh representation
  (surface reconstruction)
• …

• Cut/engrave flat sheets with a laser
• Supports many materials (wood, metal, paper, acrylic, …)

• Mirrors direct laser beam to precise (x, y) location
• Laser intensity/exposure time tuned for the material and desired effect (cutting vs engraving)

• Great for fabricating 2D or 2.5D designs
• Can also produce 3D shapes:

• Slice 3D object into many layers
• Fabricate layers one at a time, from bottom to top

• Fused Deposition Modeling (FDM)
• Stereolithography (SLA)
• Selective Laser Sintering/Melting (SLS/SLM)
• Material Jetting (MJP)
• …

• Advantages
  • Excellent resolution (25um layer height)
  • Layers almost perfectly bind; isotropic properties
  • Wide range of resins to choose from
• Disadvantages
  • Requires cleaning and curing postprocess (place in UV oven)
  • Color and mechanical properties shift over time as curing continues
  • Only one material at a time

Laser shines on a bed of plastic or metal powder, fusing or melting the particles into a solid part.

The defect on the overhanging feature is caused by insufficient support; support structure required.

SLA can print overhangs, but not local minima (e.g., bear hand).

Stringing can be fixed by lowering temperature/speed or asking printer to retract filament.

Gaps can be fixed by increasing the extrusion rate.

First few layers can warp/peel from build platform.

Consider printing on “raft.”

What exactly can we optimize?

• Printing parameters
• Support structure
• The design itself

• Adjust orientation/slicing to
  • minimize print error
    
  • keep prints fast: use adaptive slicing!
    

These branching supports use 75% less material than the manufacture’s default support structure–reduce print time/cost.

(Note: part orientation matters here too!)