This dissertation addresses the development of a Solid Freeform Fabrication process, Selective Laser Pyrolysis, to fabricate three-dimensional porous ceramic preforms from ceramic powders and preceramic polymers. It contributes to a better understanding of the physical and chemical phenomena that intervene in this process. During this study, modeling tools were adapted and characterization techniques for porous parts were developed. The first part of this work describes the fabrication of porous preforms by using Selective Laser Pyrolysis. The choice of the fabrication process is discussed, as well as the choice of the materials used. The selected materials are characterized and methods to associate them are investigated. Finally, the microstructures of the resulting porous preforms are characterized. The second part of this study is devoted to the fundamental understanding of the various phenomena occurring during the fabrication process. These phenomena are characterized or modeled. The laser-matter interaction is investigated, and a thermal model adapted to the system is proposed. This model takes into account the laser-matter interaction, the non-linear heat diffusion process and the varying properties of the materials during the process. Results of simulations are compared with experimental data that empirically validate this model. Standard characterization techniques of mechanical properties are not adapted to porous preforms fabricated in this work. Therefore, an indentation technique is developed to evaluate the effect of process parameters on the mechanical behavior. Results of simulations with the thermal model and indentation tests are used to optimize the fabrication process.