The GreenLab model emphasizes modeling natural plants according to the physics approach rather than adhering strictly to computer science methodologies. It forms the basis of the Gloups software, which creates detailed two-dimensional (2D) and three-dimensional (3D) representations of plant structures by simulating meristem activities. This chapter delves into the intricacies of the GreenLab model and how it translates into the Gloups software's graphic generation process. The chapter begins with a review of various plant simulation models and then narrows in on the GreenLab model, detailing its parameters and constraints that shape the graphical output. The GreenLab-based computer simulations construct plant topologies using nested substructures like Russian dolls and convert them into architectural models, with photosynthesis and harvest considerations being optional depending on the study's focus. The construction of the geometric structure uses vector operators, which are described in detail. The longevity of such software is contingent on regular updates to reflect technological progress and theoretical evolutions. Despite the need for further refinement for commercial application, the Gloups software's versatility and Matlab compatibility suggest a promising future for its use in plant modeling.