gen_tree

A program to generate simple tree models for lighting simulations based on gap fraction measurements and tree shape & dimension.

Terms of use

The code is licensed under GNU. For use of the code in research, kindly cite our associated publication Measuring light through trees for daylight simulations: a photographic and photometric method.

Features

Generate tree crown models based on four shapes:

• Hemisphere
• Truncated ellipsoids (Prolate and Oblate ellipsoids)
• Truncated cones

Contents

All code is provided in the gen_tree folder.

• Library file
• Main file with example runs

Dependencies

• Python >= 2.7
• Numpy/Scipy

How to use

1. Download the code using git clone https://github.com/C38C/gen_tree.git on the command line/Terminal.
2. Run main file with python main.py, using the necessary generating function in the file for the desired shape (gen<shape_name>).
3. Results are stored in an output/ folder that contains:
   • A <shape_name>.obj file, for use with any 3D CAD program (e.g., Rhino),
   • A <shape_name>.rad file for Radiance,
   • A <shape_name>PointCloud.csv file with the initial vertices coordinates.

Getting started

The code has some default values to generate a tree crown model in the shape of a hemisphere, truncated cone, ellipsoid prolate and ellipsoid oblate.

To create your own tree you will need:

1. vertices_count which determines the number of triangles that make the tree crown model. A good number to start with is 20,000.

2. gap_percentage value, which indicates the transmittance characteristics of the tree crown. If you have a gap percentage of 10% then input the value as 0.1 in the code. Some measured gap percentages of tropical trees are given below. Follow the published paper to measure gap percentages of trees.

3. Depending on the shape you decide for the tree crown, you will need either the radius or the radius and height of the crown.

Common name (scientific name) of tree	Gap Percentage	Tree crown shape
Sandbox Tree (Hura Crepitan)	10.7%	Hemisphere
Star Apple (Chrysophyllum Cainito L.)	8.8%	Hemisphere
Bornean Rhu (Gymnostoma Nobile)	17.8%	Cone
Rain Tree (Samanea Saman)	7.4%	Ellipsoid Oblate
Red Frangipani Tree (Plumeria Rubra)	16%	Ellipsoid Prolate / Oblate

Image created in Rhino + Radiance using the tree crown models generated using the code. Above: Photographs of the scene. Below: Rendered images of the scene.