VISmaF: Synthetic tree for immersive virtual visualization in smart farming

Biological models of plant growth and growth simulations have been one of the most rapidly growing scientific fields in the last 20 years. Botanists and computer scientists have worked to create in silico alternatives of plants and natural elements resulting in models used in a variety of scientific areas. For example, in botany virtual plants and their biological models are used to evaluate physiological parameters. Having a 3D geometric model as output helps researchers to visually validate biological processes such as the interaction of plants with changing ambient light, position relative to other plants, or changing temperature. Virtual plants are also used in ecology to visualize information of non-visible processes, making scientists aware of processes such as plant development in reaction to disease or stress and plant growth after pruning. The work presented here has the goal to create a synthetic tree in a real-time 3d environment that grows according to mathematical biological rules. In particular, the tree model is able to react to changes in the external virtual environment, such as a change in direction and amount of light. In order to obtain 3D structure from dynamic system models based on biological processes, a link has been created between a system of ordinary differential equations (ODEs) and the real-time 3D rendering engine Unity. The link works in both directions: the ODEs system calculates the growth of the meristem in length at each set time-step (e.g. one day) which will be the input for the 3D engine to create the structure; the input parameter for the ODEs system is calculated in the 3D environment and can be the amount of light, temperature or other species-specific growth parameters. In the present work, the system grows the synthetic tree until a given concentration of inhibitor is reached, after which the tree enters a seasonal growth stop and then starts growing again after the inhibitor concentration reaches a minimum. Upon resumption of growth, the synthetic tree will generate one or more branches depending on the species-specific parameters set. The branching angle, like the calculated elongation of the meristem, is a function of the calculated amount of light, simulating phototropism. The amount of light is calculated using a custom shader in unity. The proposed approach is capable of integrating time process-based mathematical models of biological systems in 3D engines. The modularity of the system allows the independence of the 3D rendering from the biological mathematical part allowing, if necessary, the change, optimization, or improvement of the mathematical model underlying the simulation. This can provide several advantages in the field such as seeing at a glance if a certain model is related to reality, modeling future trends of plantations for productive purposes, evaluate possible interventions and display the results in a clear way for end-users. Further studies are underway in this direction to improve both biological modeling and 3D engine rendering.