GreenLab Course
Development
3D Structure construction
3D structure construction
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Computing plant 3D geometry
Once the topological structure has been built, 3D geometrical construction can be performed.
This construction is defined in two steps
- computing axis position and orientation, i.e. computing the first internode orientation
- computing axis shape, adding the sequence of internodes building the axis one by one.
Axis position and orientation
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The first phytomer defines the branch position and orientation.
The position of the branch is defined by its origin, set to the top of the internode bearing the axis.
The orientation is computed relatively to the bearer orientation introducing relative angle deviations due to:
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- the branching it self(the new axillary shows a branching angle with the bearer)
- the phyllotaxis angle
- where applicable, the whorl angle, if the considered phytomer rank in the whorl is not one.
The same approach is used to define the orientation and position of other organs (leaves, fruits, etc.)
Axis shape
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The total length of the axis is first evaluated (as the sum of its internode lengths)
A global deformation angle is then computed in order to simulate or mimic mechanical bending.
Then, starting from the first internode orientation, the axis is constructed internode by internode, applying local deformations, part of the global deformation and, when applicable, twists and torsions.
Note
Most of structural and FSP model implementations integrate 3D geometrical computation at early simulation stages.
In the GreenLab approach, since structure is not required to be explicit, 3D geometrical computation is a post-process.
In some implementations, this computation is not even integrated:
- plant topology is exported and geometry is generated by large range tools
- the user parametrize geometrical parameters interactively (angles, mechanics, etc.)
- the self pruning process can be added and past sequences can be reconstructed
- advanced graphics can be generated.
The following figure illustrates such an example.
From structural explicit simulation to 3D representations (Images M. Jaeger, CIRAD)
From left to right:
- The explicit 2D structure construction topology with its organs.
Three geometrical 3D structure reconstructions with various branching angles, bending and twists
The last reconstruction shows leaves.
The four 3D reconstructions were generated by the Xplo tool.
Geometrical construction (branching angles, phylotaxis, deviations, mechanical like shapes), and 3D graphics are not detailled in this course.
See references below (Jaeger et al 1992 and 2010) for more information.
Bibliography
Jaeger M., de Reffye P. 1992. Basic concepts of computer simulation of plant growth. Journal of Biosciences, 17, 3, pp. 275-291. (access to paper and pdf)
Jaeger M., Sun R., Jia J.-Y, le Chevalier V. 2010. Efficient virtual plant data structure for visualization and animation. In: Proceedings of IADIS International Conferences Computer Graphics, Visualization, Computer Vision and Image Processing 2010, MCCSIS 2010 Freiburg, Germany, July 27-29, ISBN 978-972-8939-22-9, 2010 IADIS, pp. 65-75 (pdf)
Xplo: an open source software for plant architecture eXploration : http://amapstudio.cirad.fr/soft/xplo/start