Photogrammetric Point Cloud Skeleton Abstraction

Professur
Green Technologies in Landscape Architecture
Forschungsarbeit

Living Root Bridges (LRBs) are made of aerial roots of Ficus elastica by local tribes in the Indian state of Meghalaya. To understanding the mechanical structure of the bridges, the engineer’s knowledge should be integrated. Based on point cloud data acquired by photogrammetry surveys, the aim of this study is to abstract topological models of the LRBs from noisy point clouds.

As the first study that tackles these problem, Living Root Bridge sections that consist of a variety of branch configurations are used as testing models prior to upscaling the method to a whole bridge. The final worklow consists of: 1) initialize the point cloud’s rotation by principle component analysis (PCA); 2) voxelize the point cloud with a certain resolution; 3) process the voxel model including deleting outliers and filling the hollow trunk hole; 4) thin the voxel model to a one-voxel-thick skeleton; 5) segment branches by identifying joints.
The result is a topological skeleton model of the living root branches. The quality of the result is analyzed in terms of various model rotation, deviation and restoring capabilities. Two possible uses of the topological model are addressed and tested: shape description and growth forecast.

voxel thinning
3D voxel thinning process with anchored ends in iterations
voxel thinning
3D voxel thinning process with anchored ends in iterations
skeleton and point cloud in sections
skeleton points and means point of the ladder joint model in sections
geometric descriptions
geometric descriptions of the roots based on abstracted skeleton
girth growth
girth growth simulation of the living root sections using an electric analogy