1 / 35

3D Scanning

3D Scanning. Projection. How can we get the form?. Capturing design intents. Generators Fillet radius change Knuckles. Scanning. 3D Scanning is the process of getting a set of surface points from a physical object Touch probe, optical, laser ranging, etc.

miron
Download Presentation

3D Scanning

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 3D Scanning

  2. Projection How can we get the form?

  3. Capturing design intents • Generators • Fillet radius change • Knuckles

  4. Scanning • 3D Scanning is the process of getting a set of surface points from a physical object • Touch probe, optical, laser ranging, etc. • Usually the points are structured

  5. 3D Scanning equipment • Contact type • Touch probe scanner • CMM • Non-contact type • Laser scanner • Optical scanner

  6. Touch probe scanning

  7. Co-ordinate measurement

  8. Laser range scanning

  9. Optical scanning

  10. Application range • From very small (tip of a drill bit) to very large (the Lee Ka Shing tower) • Rigid or soft • Coloured, glossy, transparent • Restrictions: Smoke, hair, cloud, very fast moving objects, etc.

  11. Data captured • X Y Z location of points • Freshly scanned data sets are usually structured, as a array in XY plane with different Z values • May become un-structured, un-even spaced in all directions after re-sampling • Usually stored as an ASCII text file

  12. Point cloud • The collection of points is called point clouds • A point cloud define the SURFACE of an object • Some scanner (like CT and MRI) can measure physical properties of a object’s entire solid mass, the collection of points is not point cloud, it is called VOXEL

  13. Level of details (LOD) • LOD is determined by point density, which is determined during scanning • LOD is proportional to file size • Scanning itself is not selective, the result file size of a flat surface is the same as a carved board

  14. Shape consideration • Optical scanner capture a 2D array of points each time • Steep surface will have less points cast on it, thus fewer details

  15. Take ‘pictures’ of the object Output a set of 3D points 3D Optical scanning

  16. Shape VS position • Point clouds gives only position information • The shape of the object, if there is any, is not defined in the point cloud data • Human can infer the shape from the clouds easily, but it is very difficult for machines

  17. Scan registration and merge

  18. Scanning and stitching • Scan the object, coat the surface if necessary • If the scan result cannot cover entire surface, scan from other angles • Use point cloud manipulation software to align and merge scan results

  19. Re-sampling • Re-sampling is the process to reduce the number of points or polygons so that the file size become manageable • Adaptive re-sampling reduce more data points on smooth surface and keep more in regions that have abrupt changes

  20. Points are only x,y,z values Alignment

  21. Positioning and scaling • Data from optical scanner is not necessary correct in size • Positioning of point cloud is not necessary suitable for surface patching • Alignment may need to be adjusted

  22. Tessellation of Point cloud

  23. Triangulation • The process of converting point clouds to polygon models • Triangulation is computation intensive • If two points are close together, they are most probably on one surface • If there are more that one possible shape, the shape that form a CONVEX HULL are more likely the correct choice

  24. Multiple solution

  25. Create curve network

  26. Feature curves • Feature curves are curves that define distinctive visual features • Sharp edges • Fillets • Holes • 3D scanning cannot capture feature curves directly • Irregularities may be corrected

  27. Repair model

  28. Surface modelling • Generate surface patches using feature curves as guide lines • Lofting is easier but may generate surfaces with unwanted undulation • Sweeping and ruling generate fair surfaces but the feature curves are more difficult to draw • Irregularities may be corrected

  29. NURBS surface creation

  30. Surface recreation • Cut Sections by user defined plane, and then create surface according to these sections • ‘Draw’ 3D feature curves directly on the point cloud • Full auto generation

  31. Steps to retrieve CAD from foam model • Scanning and stitching • Re-sampling • Automatic surfacing or manual surfacing • For manual surfacing • Positioning and scaling • Draw feature curves • Draw Surface patches • Check deviation

  32. Application

  33. Related applications • Specialised applications • Surfacer • Rapid Form • Raindrop Geomagic • Scanning modules • Pro/E, UG, CATIA, ALIAS

More Related