Abstract
Static 3D virtual plants in connection with radiation models have proven to be valuable tools to investigate the effect of single-plant architecture as well as crop structure (row and plant spacing) on light interception and canopy photosynthesis. Approaches to compute light distribution and interception in virtual plant stands include path tracing and nested radiosity. In path tracing the direction of a ray from the light source to an intercepting object, as well as its further fate (reflection, transmission, absorption), are chosen stochastically. Nested radiosity computes the irradiance over a polygon as a sum of two components, polygons nearby and farther away. We compared two different radiation models implementing these two approaches in terms of suitability and computation time efficiency. Measurements of plant architecture were conducted on five tomato plants grown on slabs in hydroponic culture. Light interception was measured at 8 different spots in the greenhouse at 25 cm interval from top to the bottom. Virtual plants were reconstructed with parametric L-systems in cpfg (in L-Studio) and XL (in GroIMP). The static cpfg tomato model was coupled with the Caribu light model, and the nested radiosity (NR) option with “infinity” was used. The static XL model was linked to the GroIMP radiation model (a Monte-Carlo pathtracer (MCPT), with one billion rays, ten reflections per ray). Both models used as light source 72 directional lights that mimicked diffuse light conditions. Stacks of virtual light sensors were placed horizontally in the scene. Both NR and MCPT gave an accurate correlation between measured and simulated values (Fig. 1). Computational time varied between 6 and 12 hours (NR) and 74 minutes (MCPT). The simulated light extinction pattern was the same for both approaches. However, in NR we observed lower light intensities in the lower canopy. Also, light intensity constantly decreased with increasing canopy depth whereas a constant or only slightly decreasing light level was observed in the lower canopy in MCPT. In MCPT an infinite canopy similar to Caribu could be mimicked by using more buffer rows. Future work will be done on exploring the effect of the size of the bounding box in Caribu and on introducing an infinite canopy to the GroIMP radiation model.
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Claims 7
Claim · model-written summary
Both nested radiosity and the Monte-Carlo pathtracer gave an accurate correlation between measured and simulated light values in the tomato canopy.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- accurate correlation between measured and simulated valuese0
- Comparator
- measurede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e0“Both NR and MCPT gave an accurate correlation between measured and simulated values”
Claim · model-written summary
Computation time of the nested radiosity (NR) model varied between 6 and 12 hours, compared with 74 minutes for MCPT.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- Computational timee1
- Value
- 6 and 12 hourse1
- Comparator
- MCPTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e1“Computational time varied between 6 and 12 hours (NR) and 74 minutes (MCPT)”
Claim · model-written summary
Computation time of the Monte-Carlo pathtracer (MCPT) was 74 minutes, compared with 6 to 12 hours for NR.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- Computational timee1
- Value
- 74 minutese1
- Comparator
- NRe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e1“Computational time varied between 6 and 12 hours (NR) and 74 minutes (MCPT)”
Claim · model-written summary
The simulated light extinction pattern was the same for both models.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- simulated light extinction patterne2
- Comparator
- both approachese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e2“The simulated light extinction pattern was the same for both approaches”
Claim · model-written summary
NR gave lower light intensities in the lower canopy than MCPT.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- light intensities in the lower canopye3
- Direction
- lowere3
- Comparator
- MCPTe4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e3“in NR we observed lower light intensities in the lower canopy”
e4“light intensity constantly decreased with increasing canopy depth whereas a constant or only slightly decreasing light level was observed in the lower canopy in MCPT”
Claim · model-written summary
In NR light intensity decreased constantly with canopy depth, whereas in MCPT the lower canopy showed a constant or only slightly decreasing light level.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- light intensitye4
- Direction
- decreasede4
- Comparator
- MCPTe4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e4“light intensity constantly decreased with increasing canopy depth whereas a constant or only slightly decreasing light level was observed in the lower canopy in MCPT”
Claim · model-written summary
In MCPT an infinite canopy similar to Caribu could be mimicked by using more buffer rows.
- Taxon
- tomato
Solanum lycopersicumt0 - Outcome
- infinite canopy similar to Caribu could be mimickede5
- Qualifier
- using more buffer rowse5
- Comparator
- Caribue5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
t0“tomato”
e5“In MCPT an infinite canopy similar to Caribu could be mimicked by using more buffer rows”