I'm currently trying to spread pebbles along a plane using particle systems. Moreover, I wanted it so that it only spread on certain areas of the plane (which can be done using weight painting & adding a vertex group).
The problem is, whenever I tried to weight paint the plane, nothing shows up in my 3D viewport. No red/colors that usually appears during weight painting.
Please take a look at this 'blend file', and see what's wrong with my weight painting. I'm pretty confident that it should've worked like normal.