Exa-MA WP1 - Terrain Internship Report

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Internship conducted by Giulio Carpi Lapi under the supervision of Vincent Chabannes


August 23, 2024.


1. Abstract

This internship took place at Cemosis (Center for Modeling and Simulation in Strasbourg), hosted by IRMA (Institute for Advanced Mathematical Research) at University of Strasbourg, France. It lasted 8 weeks, from the 11th of June to the 6th of August, 2024.

Cemosis is participating in the PEPR Numpex (Priority Research Program and Equipment for Numerical Exascale computing) through the Exa-MA (Methods and Algorithms for Exascale) project. Within this context, Cemosis aims to scale the Ktirio Urban Building application to exascale power. This application, developed as part of the CoE Hidalgo2 Urban Building Model use case, focuses on providing advanced tools for urban energy simulation.

A key aspect of this computational workflow is the 3D geometric reconstruction of urban landscapes. The terrain, represented by highly dense structured meshes, often contains unnecessary complexity, particularly in flat areas, due to elevation data sourced from uncompressed raster images.

The objective of this internship was to enhance the terrain mesh generation process creating constrained triangulated meshes aligned with contour lines. This approach aimed to significantly reduce the mesh size while maintaining or improving the precision of the original meshes, or at least ensuring controlled distortion.

During this internship, I collaborated with colleagues working on several projects within Exa-MA WP1 (Work Package 1), focused on discretization for the Exa-MA project. These projects included:

  • Exa-MA WP1 - Vegetation

  • Exa-MA WP1 - Urban Building LOD-1

  • Exa-MA WP1 - Urban Building LOD-2 and Kinetic

  • Exa-MA WP1 - Performance and Scalability

The overarching goal was to recreate a comprehensive urban model by integrating various urban elements, such as buildings and vegetation, into the terrain meshes to develop a detailed 3D model of the urban landscape. While my colleagues focused on specific components, some on vegetation elements and others on building models, the integration process will ensure that all these elements combine seamlessly.

This internship was conducted by Giulio Carpi Lapi under the supervision of Vincent Chabannes, research engineer at IRMA.

Special thanks are extended to Christophe Prud’homme, head of Cemosis, Pierre Alliez, senior researcher and team leader at Inria (National Institute for Research in Digital Science and Technology) and to Christos Georgiadis, post-doctoral researcher at Inria, for their valuable contributions.

2. Introduction

2.1. Context

2.2. Main Objectives

2.3. Software and libraries

3. Methodology

3.1. Pre-existing Codebase

3.2. Configuration

3.3. Data acquisition

3.4. Map and tiles coordinates

3.5. Mapbox Terrain-RGB v1 API

3.6. Constrained Delaunay triangulation

4. Implementation

4.1. Project structure

4.2. Mesh generation

4.3. Contour lines generation

4.4. Re-triangulation

5. Results

5.1. Exporting and visualization

6. Prospects

6.1. Handling and merging multiple tiles

6.2. Mesh refinement

6.3. Parallelization

6.4. Urban elements integration

7. Conclusion

7.1. Conclusion


References