add workshop: "Integrate a 3d computational library in QGIS"

Code-Sprint-QGIS-Grenoble,-March-2024.md

@@ -104,6 +104,18 @@ The landscape of ETL is changing a lot these days with the end of Talend open so
 - Florent Fougères will introduce Oslandia's work in progress about listing QGIS modeler features VS FME and some key features missing in QGIS 
 - Valentin Buira will present a very nice GSoC project to revamp QGIS modeler UI, heavily inspired by node-based applications outside the GIS world, especially the open source software Blender.
 
+#### Integrate a 3d computational library in QGIS
+
+Lead: Loïc Bartoletti and Jean Felder
+
+timing : 1h30
+
+`QGIS` relies on some 3d algorithms for `QGIS 3D` and the elevation profile tool. However, it does not use an external 3d computational library which can result on some issues and limitations. For example, `QGIS 3D` is not able to properly [display a 3d line](https://github.com/qgis/QGIS/issues/56158) because of the lack of a 3D buffer algorithm. Besides, the elevation profile tool is not able to properly handle [some edge cases for lines and polygons because there is no 3d intersection](https://github.com/qgis/QGIS/pull/54964#discussion_r1502939991).
+
+There are a lot of libraries to handle these 3d algorithms. However, `SFCGAL` seems like a good fit for a `QGIS` integration because it suits well in the `OSGEO` ecosystem and it is already used by `postgis` and `gdal`. 
+
+This workshop aims to present a study in order to add `SFCGAL` as a new QGIS optional dependency. `QGIS` already provides `geos` integration by using a class named `QgsGeos` which inherits from `QGsGeometryEngine`. `SFCGAL` could use a similar approach by creating a new `QgsSFCGAL` class and integrate some popular 3d algorithms such as buffer and intersection. 
+
 ### Afternoon
 
 #### QGIS security process, how to prepare to CRA obligations ?