Modelling Trees with FME
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The document discusses the use of FME for modeling trees in Täby, Sweden, highlighting the municipality's limited resources and the tools available for tree identification and visualization. It outlines a process for filtering point cloud data to isolate tree representations, extracting their positions, heights, and diameters, and then replacing them with 3D models in SketchUp. The presentation emphasizes the importance of trees in creating an attractive 3D city model and invites feedback from the FME user conference participants.
Modelling Trees with FME
- 1. Modelling Trees with FME
- 2. FME User Conference 20 22 Jonas Nelson GIS Coordinator Municipality of Täby, Sweden
- 3. 20 22 FME User Conference 15 km north of Stockholm 70 km2 75 000 inhabitants
- 4. 20 22 FME User Conference ”The world needs trees. This goes for 3DCMs and digital twins as well.”
- 5. 20 22 FME User Conference Agenda ● What do we want to achieve? ● What do we have to work with? ● How do we use FME?
- 6. 20 22 FME User Conference Central Täby Looks so much more attractive with trees!
- 7. 20 22 FME User Conference What do we have to work with? Being a local government, we have limited economic resources. ▪ Hi-res LIDAR point cloud – unfortunately without vegetation class. ▪ Buildings – both as 2D footprints and 3D-models (made partly with FME). ▪ Raster orthophotos (for draping). ▪ FME Desktop ▪ SketchUp The point cloud class ”Unclassified” contains trees, but also cars, lamp posts, balconies, construction cranes, road signs, etc.
- 8. 20 22 FME User Conference How do we use FME? ▪ Find possible tree areas ▪ Position, height, diameter ▪ Replace with a 3D model Point cloud without vegetation class The result, combined with 3D buildings and an orthophoto, is something amazing!
- 9. 20 22 FME User Conference FME will help us with three things 1. Which of the points in the point cloud might represent trees? 2. Where are the individual trees? Get their position, height, and diameter. 3. Replace the trees with scaled 3D tree models in SketchUp.
- 10. 20 22 FME User Conference 1. Which parts of the point cloud might represent trees?
- 11. 20 22 FME User Conference 1. a) Read the Point Cloud
- 12. 20 22 FME User Conference 1. b) Clean the Point Cloud
- 13. 20 22 FME User Conference 1. c) Normalise heights and filter by elevation
- 14. 20 22 FME User Conference 1. d) Use only points with at least 2 returns
- 15. 20 22 FME User Conference 1. e) Turn the remaining point cloud into areas Note the long and narrow areas. These are signs above roads, beams for power lines and bridges, etc.
- 16. 20 22 FME User Conference 1. f) Delete long and narrow areas
- 17. 20 22 FME User Conference 1. g) Keep the most circular areas Large areas are chopped into ”tree-sized” parts. Circularity is calculated. We do lose some trees in this part of the process, but the overall gain is higher.
- 18. 20 22 FME User Conference 1. h) Clip the original point cloud, using the computed tree areas We now have a point cloud representing trees only (almost). Everything up to this would not have been necessary, had we had a point cloud with a class for “High Vegetation”.
- 19. 20 22 FME User Conference 2. Find individual trees and extract position, height and diameter
- 20. 20 22 FME User Conference 2. a) Create a 1x1 m grid of stacked points, by rounding …and sort to find the highest Z in each stack.
- 21. 20 22 FME User Conference 2. b) Compare each stack’s Z_max with it’s neighbours, to find local max. The size of this search buffer is important. Too large and we might miss small trees close to larger ones. Too small and every branch might turn into a local treetop. Here, we search within 2.5 m, covering the two closest candidates in every direction.
- 22. 20 22 FME User Conference 2. c) Local maximas = probable tree top Note: Trees might be leaning, and they might have more than one local max (treetop). This model does not aim to be perfect.
- 23. 20 22 FME User Conference 2. d) Create Voronoi polygons around each treetop The Voronoi polygons are limited to 8 m radius (suitable for our kind of trees, but this could potentially be another user input parameter).
- 24. 20 22 FME User Conference 2. e) Trim the Voronoi polygons using the tree areas This might split a Voronoi polygon in two (or more) parts. Keep only the one with the treetop, and only if it is reasonably round in shape.
- 25. 20 22 FME User Conference 2. f) Create Bounding Boxes and move tree position to center
- 26. 20 22 FME User Conference 2. g) Generate tree diameters The circle (tree diameter) are computed as the mean of the bounding box’ length and width. We now have everything we need for our trees to be modelled; Position, Height and Diameter
- 27. 20 22 FME User Conference From possible tree areas to individual tree objects
- 28. 20 22 FME User Conference 3. Replace the tree position with a 3D model and scale it
- 29. 20 22 FME User Conference 3. a) Read suitable 3D models of trees I use simple models from SketchUp 3D Warehouse, and also randomize between tree different models.
- 30. 20 22 FME User Conference 3. b) The final result, visualised in SketchUp
- 31. 20 22 FME User Conference Reality check Google Earth LoD2 + trees, SketchUp
- 32. 20 22 FME User Conference Trees are a vital part of a 3D City Model. FME can help you create them.
- 33. Thank You! jonas.nelson@taby.se My participation was made possible thanks to
- 34. 20 22 FME User Conference Please Share Your Session Feedback Log in & navigate to the agenda. Select the session you attended Scroll down to “Session Feedback” Download EventMobi app Event code: fmeuc Click “Launch App” Fill out the survey and submit