IMapple — Functional structural model of apple trees

Computer simulation of tree development can provide important insight into real world tree behavior. Numerous models have been developed ranging from simple equations to complicated 3D geometrical models that allow for simulation of acquisition and allocation of carbohydrates. We introduce IMapple (Interactively Modeled Apple), a functional structural apple tree model that builds on the source-sink model of L-peach. Our model integrates accurate biological functionality, as well as high quality visual geometric details. The details are modeled by using subdivision surfaces that allows for fast generation of high precision geometry and direct illumination of leaves is simulated by sampling the sky and the sun trajectory. The main advantage of the IMapple is that allows for an interactive experimentation by the way it manages data. Input data can be provided interactively or by using real-world samples and the model responds immediately. Alternatively, hypothesized data can be input by drawing functional dependencies, for example the resource assimilation rate as a function of light interception can be input by drawing a graph showing the real or assumed relationship. Moreover, our model supports a variety of convenient user interactions, such as branch pruning and flower thinning. We have collected a large data set over the last few years that serves as inputs to our model. IMapple is fast and it allows for interactive or near-interactive simulation of apple trees. For example, a ten years-old tree grown with a time step of one hour can be simulated in under five minutes using a PC. Moreover, our system allows for a simulation of multiple trees and their mutual interaction. We demonstrate the results by simulating growth and fruiting of Golden Delicious apple trees realistically with data collected from a planting at the Purdue Meigs research farm.