Normal maps are actually kind of difficult to make by hand as they encode vector data. Luckily, we can make a much simpler bump or heightmap, and then convert it to a normal map using various tools.

In a bump map, white represents areas of high elevation, and black represents low. I found the following to be useful when transferring from the colour map:

• Baseline grey level of 50%.
• Panel gaps and divets should be 40% grey (#666666).
• Everything else is up to your discretion.

Once done, export it as a PNG and use a tool like xNormal or NormalMapOnline to convert it into the customary bluish-psychedelic normal map we’ll need.

Since we used 50% grey for our baseline level, make sure you specify that in your tool’s options: for NormalMapOnline, checking Z range: -1 to +1 will do this. You will also need to flip the R value, and I tend to find halving the strength helps a lot. Save this output, making sure the final name is set to that of _BumpMap in the mu shader options in Blender.

Part of a bump map for the Hestia I made by converting parts of my colour map.

The bump map converted into a normal map with NormalMapOnline.