Using Visualea : Weberpenn



In OpenAlea, different tree architectures can be generated procedurally. OpenAlea.WeberPenn is based on the tree generating algorithm defined by Weber and Penn in 1995.

The model generates a tree structure based on a set of allometric rules. Fundamental parameters are, for instance, the overall appearance of the tree, the size of the lower part of the tree without axes, the max branching order or the curvature of the axes.


Install Visualea and Weberpenn for this tutorial

conda install -c openalea openalea.weberpenn openalea.visualea

Then, execute this


Model Parameters

Image Courtesy of Wolfram Diestel, developer of the Arbaro software.

  • General shape parameters :
    Scale and ScaleV : Global size of the tree
    BaseSize - Size of the lower part of the tree without branches

    Each other parameters are defined for each branch level (or order) with order0 = trunk

  • Branch length is specified by the user at each order and is relative to the father branch length and to the overall shape of the tree.

  • rotation (aka rotationV) define the phyllotaxis angle at each order

  • curve parameter defines curvature of branches
    curve back define inflexion angle
  • down_angle define the angle of insertion between a branch and its father


Begin with weberpenn

Once you’ve launched Visualea, in the package manager, go in demo and double-click on demo_WeberPenn.


There will see two workflows in the workspace.

Workflow 1

On this workflow, there are the global parameters, trunk, order 1, order 2, tree parameters, weber and penn and plot3D nodes. You can change some parameters by double-clicking on the nodes.

  • Global parameters change main parameters of the tree like its shape


  • trunk, order 1 and order 2 allow to change parameters of the current order


  • tree parameters synthesizes all the parameters into a unique global parameters object

  • weber and penn computes the scene with all the generated surfaces

  • plot3D displays a 3D-scene

Right-click on the plot3D node and click on “Run”. The scene will appear and you’ll be able to see the tree architecture corresponding to the inputs you’ve entered in the parameters nodes


You may want to change some parameters and see the impact on the tree architectures in real time. To do this, right-click on the plot3D node and click on “Mark as User Application” then run the node. Now, when you change a parameter, the scene updates instantly. Have fun !!!


Workflow 2

On this workflow, it is the same as the Workflow 1 but you only have to choose the species you want in the species node. There are 3 species that have been preset.