Hi everyone!
I found a post on a manipulation of QGIS (available here) which is exactly my goal to make a sort of heat map based on a grid (the grid is defined by the user) from a given point, or initial polygon! (The explanations are clearer on the link!)
The ultimate goal is to publish a kind of workflow via Model Builder on ArcGIS Server and use it through the Web AppBuilder ESRI via the JS API, so if you have a tip for this kind of workflow used directly in JS API, I'm really interested!
Thank you in advance for your help !