Quick Tutorial

This is a quick overview of the PypeTree UI and basic features.

Point Clouds

A point cloud is a set of 3d points:

  • You can load an existing one with File->Open (point cloud files must have an .asc extension).
  • A new point cloud can also be created by sampling an artificial L-System model with Model->L-System.
  • Once a point cloud is on screen, it can be downsampled with Point Cloud->Aggregate, or have its branched clipped at a certain geodesic distance with Point Cloud->Geodesic Clipping.
  • If an articulation sphere is highlighting some of its points (View->Point Cloud->Shere Selection), pressing D while the sphere is selected will delete them, thus pruning the point cloud.
  • At any time, the current point cloud can be saved with File->Save Point Cloud.


A model is a set of truncated cones linked together to form a tree, in both the mathematical and botanical senses of the word (i.e. it’s not possible for a “child” articulation point to have multiple “parents”, or in other words, for a branch to be linked to many trunks). There are three ways a model can be generated:

  • By loading an existing one with File->Open (model files have a .pkl extension)
  • With the Modified Verroust & Lazarus reconstruction algorithm (Reconstruction->Modified Verroust & Lazarus)
  • As a temporary structure in step 1 of the L-System modeling process

The interesting thing about models is the way you can interact with them. The interaction mechanism works with articulation spheres. To create one, double-click near a model articulation point (i.e. at the junction between two segments), it will appear there.

To help with spatial navigation, these spheres perform a point selection (if a point cloud is present). To modify the model structure with a sphere, it must be first selected, by pressing s while the cursor is over it (it then becomes blue). Once a sphere is selected, you can:

  • Modify the position of the corresponding model articulation (by dragging it) or its radius (while holding the right button):
_images/sphere_before.png _images/sphere_after.png
  • Delete it, by pressing d (this won’t affect the model anyhow)
  • Cut the branch segment above it, by pressing x:
_images/cut_smallx_before.png _images/cut_smallx_after.png
  • Cut the whole branch to which it belongs, down to the nearest branching point, by pressing X:
_images/cut_bigx_before.png _images/cut_bigx_after.png

Finally, when a point cloud is present, it’s possible to double-click on it to create a “roaming” sphere (i.e. not attached to any model). If it is selected, you can then connect this sphere to a model by pressing c while the cursor is over the desired link point:

_images/connect_before.png _images/connect_after.png

Of course since this is a tree model, only one such connection is allowed for a given sphere.

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