# Enhancing 3D Printing with Procedural Generation and STL Formatting Using Python
## 3 Materials and Methods
Esri's CityEngine (Esri [29]) is a procedural modeling tool designed specifically for generating large-scale urban environments. It uses rule-based systems to create city layouts, building structures, and landscapes. In urban planning and architecture, it is used for the creation of virtual cities for games and simulations and the visualization of urban development projects. A mathematical formalism, the L-System (Lindenmayer System) [30], is used to simulate plant growth processes and is implemented in various tools and software for the procedural generation of plants and trees. Its main applications include generating realistic vegetation in games and movies, simulating natural growth patterns, and creating complex organic structures. The SpeedTree (Interactive Data Visualisation [31]) software package is designed to model, texture, and animate trees and vegetation by using procedural techniques. It is widely applied in the film, games, and architectural visualization industries to generate realistic trees and plants, create dynamic leaves swaying in the wind, and fill virtual environments with vegetation. Terragen by Planetside Software (Planetside [32]) is a tool for creating and rendering realistic landscapes and planetary environments. It uses procedural algorithms to generate terrain, skies, and ecosystems; develop landscapes and environments for movies and games; simulate extraterrestrial environments; and generate high-resolution terrains. Unity [33] and Unreal Engine [34] are popular game development engines that support procedural generation through various plug-ins and built-in tools. Unity uses tools such as ProBuilder and procedural asset generation packages; however, Unreal Engine (Unity Technologies, San Francisco, CA, USA) offers Blueprint scripting and procedural mesh generation to procedurally generate levels and dungeons, create dynamic and interactive environments, and generate textures and materials. The procedural terrain generation tool, World Machine (World Machine [35]), is applied to create realistic landscapes. It provides tools for simulating erosion, terrain sculpting, and texture generation, and its applications enable generating terrain for video games and simulations, creating realistic landscapes for film productions and enhancing geographic visualization projects. Another terrain design tool, GAEA (QuadSpinner [36]), combines procedural generation with manual sculpting. It offers advanced erosion and sediment simulation tools for realistic terrain creation. It is applied to create detailed terrain for games and films, simulate natural geological processes, and design large-scale environments. Modular product design can be efficiently processed using existing CAD software through configuration control and parametric modeling. However, the application of mesh geometry presents unique challenges and opportunities. Below is a detailed comparison of why recognizing mesh geometry as a combination of features for further design purposes can be beneficial or why it can be difficult compared to using a boundary representation (B-rep)-based environment in standard CAD. We compare mesh and B-rep-based environments. The B-rep (standard CAD) geometry-based environment has the following advantages: precision and accuracy (B-rep models provide precise mathematical descriptions of surfaces and edges, ensuring high design and manufacturing accuracy); feature recognition and parametric design (CAD software perfectly recognizes and manipulates features (e.g., holes, fillets, ridges), allowing easy modifications and parametric adjustments); history-based modeling (CAD environments typically support history-based modeling, where design changes are tracked and can be easily updated or rolled back); and integration with simulation and analysis (B-rep models integrate seamlessly with simulation and analysis tools (e.g., FEA, CFD), providing accurate input data for performance evaluation).