# Open Phd position: Modeling and processing of multi-material volumes

# Contacts

Cédric Zanni (cedric.zanni@loria.fr) and Sylvain Lefebvre (sylvain.lefebvre@inria.fr).

# How to apply

Follow the link http://doctorat.univ-lorraine.fr/fr/les-ecoles-doctorales/iaem/offres-de-these/modelisation-et-traitement-de-volumes-multi-materiaux to apply.

# Context

Additive manufacturing completely changes the way objects can be produced. On the one hand, it simplifies the manufacturing process itself, allowing everyone - including the general public - to physically realize a virtual model using a 3D printer. On the other hand, it affords for unprecedented possibilities in terms of shape complexity, both at the macro and micro scales: objects can be filled with multi-material structures that vary in size, orientation and shape to give specific properties to the final parts. Unfortunately, describing shapes at this level of customization, scale and complexity is beyond the reach of current software. The challenge lies in how to specify shapes than can be easily manipulated, optimized for properties, as well as visualized during manipulation and prepared efficiently for the manufacturing process. A key technical choice is that of shape representation. Boundary representations (e.g. triangle meshes) are very effective to represent surfaces. However, additive manufacturing blurs the frontier between surfaces and volumes. Implicit volumes, a mathematical definition which computes whether a point is solid or empty, provide an efficient scalable representation. Such approaches are referred to as procedural and can be used to represent both material – such as colors [YZG11,YY12,VKWM16] - and microstructures [MDL16,MHSL18,TT20] the latter being a key advantage of additive manufacturing. Variation in the microstructures or material composition can be driven by specifying different parameter inputs to the evaluation procedure based on spatial position. The control field defining those parameters is itself an important part of the design. There is currently a lack of methodologies to author, manipulate and process such property driving fields.

# Objectives

The main objective of this project is to explore representations for the modeling, visualization and processing of material control fields within the authoring pipeline for additive manufacturing with a focus on the problem of localizing and assembling different materials in an embedding object. We will first study multi-valued field functions combined with sharp or blended boundaries, representing different colors or/and material parts/structures inside a bounding surface. Contrary to all previous work on blending [GBC*13,ZGC15], the main focus will be to control the magnitude of the generated gradients instead of focusing on the localization of the iso-surface of interest. Then, we will study the extension of developed representation and algorithm to management of set of parameters of more advanced material properties and micro-structures, resulting in multi-valued field functions including non scalar parameters such as frame fields to control direction of anisotropy.

# Candidate profile

The candidate must have good programming and mathematical skills (especially linear algebra) and be able to communicate in English. Knowledge of computer graphics is also expected. An interest in GPU programming will also be appreciated.

# General information

- Location: Loria, Nancy - Grand Est
- Duration: 3 years
- Starting date: 1st September 2024
- Applications to be sent as soon as possible

# References

- [GBC*13] O. Gourmel, L. Barthe, M.-P. Cani, B. Wyvill, A. Bernhardt, M. Paulin, H. Grasberger : “A gradient-based implicit blend”. ACM Trans. Graph. 32, 2 (2013).
- [ZGC15] C. Zanni, M. Gleicher, and M.-P. Cani. : “N-ary Implicit Blends with Topology Control”, Computer & Gaphics, Elsevier, Volume 46 (2015)
- [MDL16] J. Martínez, J. Dumas, S. Lefebvre : “Procedural Voronoi Foams for Additive Manufacturing”. ACM Trans. Graph. 35, 4 (2016).
- [MHSL18] J. Martínez, S. Hornus, H. and H. Song, S. Lefebvre : “Polyhedral Voronoi diagrams for additive manufacturing”, https://hal.inria.fr/hal-01697103 (2018)
- [SMW18] P. Sahbaei, D. Mould and B. Wyvill. Implicit Representation of Inscribed Volumes. Proceedings of EXPRESSIVE, 2018.
- [TT20] T. Tricard, V. Tavernier, C. Zanni, J. Martínez, P.A. Hugron, F. Neyret and S. Lefebvre . Freely orientable microstructures for designing deformable 3D prints. ACM Transactions on Graphics, 39(6), 2020.
- [YZG11] Y. Yu, K. Zhou, B. Guo. Multiscale vector volumes. ACM Trans. on Graph., 30(6), 2011.
- [YY12] Z. Yuan, Y. Yu and W. Wang. Object-Space Multiphase Implicit Functions. ACM Trans. on Graph., 31(4), 2012.
- [VKWM16] K. Vidimce, A. Kaspar, Y. Wang, W. Matusik. Foundry: Hierarchical Material Design for Multi-Material Fabrication. In Proceedings of the 29th Annual Symposium on User Interface Software and Technology (UIST ‘16). 2016.