This video provides an introduction to the QGIS graphical modeler. It was created using a pre-release version of QGIS 3.0 (scheduled to be released Dec 8, 2017). My understanding is that many of the actual algorithms have been reworked under the surface to increase performance, but there are only very minor changes to the graphical modeler user interface. If you are using QGIS 2.xx you should have no problems following this video, although I believe that any models created in 2.xx will need to be redone in 3.xx.
What is the graphical modeler?
If you are used to working in the ESRI ecosystem and are not familiar with the graphical modeler, it plays the same role as the Model Builder in ESRI products. I’m not certain that it is quite as powerful as Model Builder because there are no iterators or branching tools. Nevertheless it allows you to chain together several processing algorithms (geo-processing tools) to perform fairly complex geoprocessing tasks. I found it quite easy to learn and use.
The QGIS geo-processing framework
QGIS has a stunning array of geoprocessing algorithms available for free. It includes well documented and thoroughly tested algorithms from GDAL, GRASS, SAGA, LAS Tools (Lidar processing) and others. It also has the ability to work with algorithms written in R. Like QGIS, all of these algorithms are open source and so, if need be, you can see the actual source code so you can verify exactly what is being done.
This openness can be very important in scientific research applications. Many algorithms published in the scientific literature are implemented first in one or more of these open source toolboxes. Many other tools such as difference and smoothing algorithms for vector layers and most raster processing algorithms are only available with extensions or advanced licensing levels in the ESRI ecosystem.
This video is a combination of two out of about 70 lectures in a course I am creating called QGIS 3.0 for GIS Professionals that should be available within a few days of the release of QGIS 3.0. For more information on this and other courses please see my courses page.