Bump Map with Gimp 2.10.8

[Ofnuts]

The tutorial is for Gimp 2.8 and you are on 2.10. Lots of change in the tools.

Bump mapping is not that hard to understand even without a video: you just need:

• The layer that will be the target (the one to which you add bumps and dimples)
  
• The "bump map" layer. It works like a "relative altitude" map. In the usual case:
  • What is gray 50% RGB(127,127,127) on the map remains at the initial level in the target image,
    
  • Darker areas correspond to lower altitudes (dimples)
    
  • Lighter areas to higher altitudes (bumps).
    
  • If you have sharp level transitions, you get the equivalent of cliffs, while progressive blends create slow slopes.
    
• IIRC Gimp requires the two layers to have the same size.
  

Everything else is just how the light simulates the relief. Since the bump-mapping creates shadows and lights, it works best on layers with an average luminosity (difficult to create shadows over pitch black...).