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Jan. 2014 Visualization with 3D CG Masaki Hayashi Digitization.

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Presentation on theme: "Jan. 2014 Visualization with 3D CG Masaki Hayashi Digitization."— Presentation transcript:

1 Jan Visualization with 3D CG Masaki Hayashi Digitization

2 Today’s contents Digital camera Laser scanning Photogrammetry (break) Agisoft “Photoscan” + Filming

3 Digital camera

4 Spec of digital camera 8 megapixels (=8,000,000) :iPhone 18MP :Consumer digital camera 60MP :Hasselblad Consumer: approx. 16MP to 24MP Hasselblad : 40MP to 60MP 8M: 3465x M: 4896x M: 8944x6708 Requires good lens for high-resolution Resolution:

5 Spec of digital camera Focal length Fixed or Zoom human eye sight ≒ 50mm (35mm film equivalent) Resolution Lens flare Lens ghosting Distortion Optical aberration Barrel Pincushion Lens: Ghosting Flare

6 Spec of digital camera 8 bit (eg: compact consumer: JPEG, TIFF) 12,14 bit (eg: high-end consumer: RAW) 16 bit (eg: Hasselbad: RAW) With RAW data, you can adjust (Processing) - Dynamic range (lightness) -Color temperature (white balance) -Edge enhancement -Uncompressed Etc. Bit depth:

7 Lighting Fill light Main light Back light Translucent backdrop (white and frosted plate) artifact Camera (from the bottom)

8 Laser scanning

9 Range: Very small object (eg. tooth), Middle (eg. Statue), Very large (eg. ruin, city landscape) + Aerial (Huge area) Output: 3D point cloud, basically. x, y, z coordinates + I(intensity) + r, g, b(color)

10 How does 3D Scanner work? Short-range ( < 1 m ) Laser triangulation Structured light Middle-range (10m) Travel Of Light (TOL): Phase shift Long-range ( > 100m ) Travel Of Light (TOL): Pulse

11 Short-range ( < 1 m ) Laser triangulation Sensor Lens Object Laser Structured light Known Calculated by 3 values Measured L sinβ sin (α + β) D =D = (α) (β) (L) (D) Sensor Lens Object Linear patterns Triangulation (more accurate)

12 Long-range ( 100 m ) TOL (Travel Of Light) Sensor Lens Object Laser Measure the TOL c (m/sec) = 299,792,458 Out In TOL TOL (phase) Out In Pulse modulation Phase modulation (more accurate)

13 Laser scanning Multiple measurements: Compensation of the shadow Planning: Locations Angle of view Resolution

14 Laser scanning Beam expansion Spot diameter is bigger when range is bigger eg. 12mm at 5m  97mm at 500m Depending on material Diffuse on the surface (clod, solid, reflective…) Angle of the beam when the beam strikes the surface Error:

15 Laser scanning Minolta-Konica Vivid 9i Example video

16 Laser scanning Some scenes

17 Laser scanning Cleaning of point cloud and filtering of the noise Point cloud to polygon conversion Filling of holes of the mesh Elimination of abnormal faces Decimation Texturing Exporting Post-processing:

18 Photogrammetry

19 Good point: Texture color is more realistic. Bad point: More errors. Range: Almost same as scanner Small object (eg. vase), Middle (eg. Statue), Very large (eg. ruin, city landscape) + Aerial (Huge area) Output: 3D point cloud + Color x, y, z + r, g, b

20 How does photogrammetry work? Camera Object 3D position can be calculated if the camera parameters are known by triangulation Camera Camera parameter: x, y, z, rx, ry, rz, AngleOfView Known points (Feature point) All the calculation is automatically done at a time Don’t get the software confused to get feature points.

21 Photogrammetry Some points: Field of View Standard : 50 degrees Tendancy: Less accurate with wider lens Focusing To get enough depth of field Lens distortion You may need to measure the distortion Reflective material Causes the error regarding the feature points Scaling Photogrammetry measurement is dimensionless Accuracy Accurate in “x-y”, not so much for “z” (laser scanning has better accuracy of Z)

22 Recent tech Better Reality : Thorskan

23 Recent tech


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