Liyu Tang

Light interception efficiency analysis based on three-dimensional peach canopy models

Light interception capability is a critical factor affecting the growth, development, fruit yield and quality of fruit trees; thus, it is beneficial to cultivate optimal canopy types with high light interception efficiency. In this study, we present a quantitative method of analyzing light interception by tree canopies based on a virtual plant model. A detailed three-dimensional (3D) peach model with a natural growth shape was reconstructed and then the branches in the model were pruned to generate canopies with an open center form. These models were used to calculate the light interception and corresponding net photosynthesis. A solar radiation transfer model was used to determine the radiation intensity at the top of the canopy, and a ray tracing algorithm and turtle algorithm were utilized to simulate the spatial distribution of direct and diffuse radiation, respectively, in the tree canopy and obtain the photosynthetically active radiation (PAR) for each leaf. In the final step, we applied the photosynthesis model to calculate the canopy net photosynthetic rate. To compare the light interception efficiency among various plant canopy shapes, the net production rate at the whole-canopy scale and the average net photosynthetic rate per unit leaf area were calculated. The simulation results showed that peach canopies with an open center form provided better results compared with canopies with a natural form in terms of light penetration and air ventilation. Our method supports quantitative analysis of light interception and use efficiency for different types of canopy architectures at each time step and for individual leaf units. The approach was implemented in the interactive parametric individual 3D tree modeling software ParaTree. The extended ParaTree software is useful for fruit tree management applications because it provides an intuitive tool that can assist in tree pruning and design for ideal canopy architecture types.

An integrated system for 3D tree modeling and growth simulation

Virtual Geographic Environments (VGEs) represent a new analytical tool for understanding geographic processes. Among the fundamental solutions to advancing and deepening the development of VGEs are geographic modeling, geographic simulation, and geographic knowledge sharing. Forest is a major component of the geographic environment. This article proposes an integrated approach for analyzing and exploring plant growth processes and the relationship between plant growth and the environment, and describes the development of a software prototype that integrates ontology, artificial intelligence (AI) and virtual plant techniques. The strategy is as follows: First, we collect existing information on the growth and development patterns, morphological structure, and environment of a chosen plant from the botany, forestry, and ecology literature. Then, we construct an ontology framework to organize the collected information and individual cases into a knowledge base and support the inferential reasoning, botanical modeling and simulation. Through rule-based reasoning (RBR) and case-based reasoning (CBR), complex relationships between tree growth and the environment can be extracted. Next, the newly derived knowledge is integrated with a 3D method for modeling the growth of individual tree based on the same ontology framework. Finally, based on the description of the tree species, environment, growth stage, and phenophase, among other factors, key tree morphology parameters are derived via semantic reasoning. Using these parameters, a new 3D tree model is generated that is consistent with the specific habitat and growth phase. Our approach is useful for users who have little knowledge of botany or who lack the computer skills to construct realistic 3D tree models that are faithful to botanical features.

Information management oriented virtual forest landscape construction and its applications

Computer modeling and visualization of forest landscapes recently has become a hot topic of research in the fields such as ecology, forest management, physical geography and botany. We reviewed multi-scale forest modeling and visualization and related rendering techniques. The principle and a technological framework of information management oriented virtual forest landscape construction are proposed, which integrate an interactive 3D subsystem with a GIS-based 2D forest resource management subsystem, taking Zhangpu County forest in Fujian Province as a pilot study. The system has capability for individual tree modeling, realistic forest stand 3D scene construction, and navigation, interactive information query, analysis, and simulation of the forest growth under the conditions of tree competition and thinning in 3D environment. In addition, future works are discussed in conclusion.

A 3D individual tree modeling technique based on terrestrial LiDAR point cloud data

Terrestrial Laser Scanner (TLS) has been used to record three-dimensional (3D) point cloud data of trees, and this data is being further processed to extract morphological parameters of standing trees and reconstruct 3D geometric model. We present an efficient, high-accuracy and photorealistic 3D single tree reconstruction technique based on the point cloud of individual standing tree acquired mainly from TLS. Our method can process point cloud data of the whole tree directly without the need to first segment data into leaves and branches. It also allows user to interactively edit and adjust model parameters to better fie the data.

Simulation and visualization of forest fire growth in an integrated 3D virtual geographical environment - a preliminary study

It is important to understand how wildland fire is spreading in a given forest landscape as this information is critical to many applications such as emergency response and decision support for fire suppression, prescribed burning, fire prevention education and fighting training. We review the progress in fire spread simulation and virtual forest modeling, and present a 3D forest fire spread simulation and visualization system. Methods and techniques for modeling and visualization of terrain, trees and vegetations and fires are discussed and incorporated with fire spread simulation and visualization system. An integrated environment was built based on OntoPlant, a suite of virtual plant software developed in house, FARSITE fire simulator developed by the USDA as fire spread engine and Open Scene Graph (OSG). The system can display a realistic 3D wildfire scenario taking into consideration the factors such as terrain, vegetation type and weather conditions. Fire is rendered by using particle system, while the level of detail and curve morphing technique are used to animate the flame and smoke under various slope and wind conditions. During the fire propagation, the appearances of burned plants are updated automatically. The fire spreading is visualized according to the calculations derived from the fire simulation engine. Greater insight can be gained as users realistically and intuitively view the fire progress in our 3D virtual forest environment.

Virtual Geographic Simulation of Light Distribution within Three-Dimensional Plant Canopy Models

Virtual geographic environments (VGEs) have been regarded as an important new means of simulating, analyzing, and understanding complex geological processes. Plants and light are major components of the geographic environment. Light is a critical factor that affects ecological systems. In this study, we focused on simulating light transmission and distribution within a three-dimensional plant canopy model. A progressive refinement radiosity algorithm was applied to simulate the transmission and distribution of solar light within a detailed, three-dimensional (3D) loquat (Eriobotrya japonica Lindl.) canopy model. The canopy was described in three dimensions, and each organ surface was represented by a set of triangular facets. The form factors in radiosity were calculated using a hemi-cube algorithm. We developed a module for simulating the instantaneous light distribution within a virtual canopy, which was integrated into ParaTree. We simulated the distribution of photosynthetically active radiation (PAR) within a loquat canopy, and calculated the total PAR intercepted at the whole canopy scale, as well as the mean PAR interception per unit leaf area. The ParaTree-integrated radiosity model simulates the uncollided propagation of direct solar and diffuse sky light and the light-scattering effect of foliage. The PAR captured by the whole canopy based on the radiosity is approximately 9.4% greater than that obtained using ray tracing and TURTLE methods. The latter methods do not account for the scattering among leaves in the canopy in the study, and therefore, the difference might be due to the contribution of light scattering in the foliage. The simulation result is close to Myneni’s findings, in which the light scattering within a canopy is less than 10% of the incident PAR. Our method can be employed for visualizing and analyzing the spatial distribution of light within a canopy, and for estimating the PAR interception at the organ and canopy levels. It is useful for designing plant canopy architecture (e.g., fruit trees and plants in urban greening) and planting planning.

Growth Simulation of Young Chinese Fir Based on Virtual Plant

Energy fixation and organic matter production of forest ecosystem were dominated by plants,which are impacted by their growth environment.The forest ecosystem has the characteristic of long life-span,which makes its research laborious and costly using field experiment.The virtual geographical environment can provide a new way for its research due to its character of trying to exceed the limit of time and space.In order to estimate the biomass and evaluate relationships among tree and environments,an L-systems based functional-structural model was developed for simulating the development of tree architecture,taking into account tree physiology and environment.The L-systems was used to represent the morphological development of tree.The basic growth unit was described in line with the development of young Chinese fir(Cunninghamia lanceolata).LSTree system integrated the photosynthesis,photosynthates allocation and morphogenesis models.The spatial distribution of solar radiation in tree canopy was simulated for calculating photosynthetically active radiation(PAR) of each leaf obtained.PAR is a key parameter for photosynthesis model to estimate biomass.The dynamic growth of an individual 3-to-4-year-old Chinese fir in Fuzhou was simulated in growing season.Based on the 2010 Fuzhou weather and Chinese fir photosynthetic characteristic,net photosynthesis rate and product were calculated for each stage.The amount of photosynthates allocated to the growth of new segments and leaves or branches and leave amplification are based on source-sink theory.The growth of tree is driven by available photosynthetic products after respiration losses were accounted for.The morphogenesis change in the young Chinese fir in response to environment was simulated dynamically in three dimensional representations.The result of net photosynthesis was compared to the previous field observation research,and it showed the simulation result was reasonable.The methodology has promising benefits to depicting the interaction of plant and environment,which will be valuable for estimation of organic matter production too.

A distributed forest fire fighting simulation system based on HLA

This paper describes the design of a distributed architecture to support an interactive, interoperable, and collaborative forest fire fighting simulation using High Level Architecture (HLA). Based on the Run-time Infrastructure (RTI) services which are specified in HLA and C++ application programming interface (API) of the RTI, The distributed virtual fire fighting environment provides a practical foundation to enhance interactivity, interoperability for distributed simulation.. Users can build new federation application by the way of the goal system reorganization. The key techniques, such as FOM/SOM design, system structure, running mechanism of simulation system are discussed.

Animating grass in real-time

Grass occurs frequently in the forest and the high performance grass generation can greatly enhance the reliability and complexity of virtual forest scenes. So the paper presents a simple method to render fields of grass, animated in the wind in real-time. We employ a series of polygons contain several grass blades to construct a basic grass unit. Animation is achieved by translate the grass units according the “wind vector” and we implement the wind effect such as a strong wind. Furthermore, we employ the rendering optimization to acquire faster frames.

Three-dimensional digitization of the arid land plant Haloxylon ammodendron using a consumer-grade camera

Abstract Plant structural parameters are important for ecological studies and for monitoring the environment. Terrestrial laser scanning has become a widely accepted technique for acquiring accurate high‐density three‐dimensional information about plant surfaces; however, this instrument is expensive, technically challenging to operate, heavy, and difficult to transport to hard‐to‐reach areas such as dense forests and undeveloped areas without easy vehicle access. Using Haloxylon ammodendron, a plant widely distributed in arid lands, as an example, we used a consumer‐grade handheld camera to take a series of overlapping images of this plant. Computer vision and photogrammetric software were used to reconstruct highly detailed three‐dimensional data of the plant surface. This surface data was compared to the point cloud of the plant acquired from concomitant terrestrial laser scanning. We demonstrated that the accuracy and degree of completeness of the image‐derived point clouds are comparable to that of laser scanning. Plant structural parameters (such as tree height and crown width) and three‐dimensional models extracted from the point clouds also agree well with a relative difference of less than 5%. Our case study shows that a common camera and image processing software can be an affordable, highly portable, and viable option for acquiring accurate and detailed high‐density and high‐resolution three‐dimensional information about plant structure in the environment. This digitization technique can record the plant and its surrounding environment effectively and efficiently, and it can be applied to many ecological fields and studies.