FOSS gamedev and creative worlds

Hi! I am the main author of the Tutorial subgame which is, for some reason only the stars could tell, still not part of the official Minetest distribution. xD

Anyways, I am here because I have recently made updates to the tutorial for explaining some of the new features in 0.4.13. One of the new features is the radar mode of the minimap (press F9).

Because the radar is not as obvious to use than the simple surface mode, I originally wanted to create an entire new section, maybe a maze in complete darkness or something and the student has to use the radar to find the way without any light.

However, this idea has failed because the radar does not work in Tutorial World. No matter where I am, no matter which zoom level I use, the radar almost always shows perfect greenness.
Sometimes the radar very briefly shows some vague structures (=less green areas), but they quickly fade away as I move around, even if just horizontally! And if I return to the spot where the structures appeared on the radar, the radar decides to have “forgotten” about the structures and it just shows green and nothing but green.

I have tried this both for versions 1.8.2 and 2.0.1 of the tutorial. There does not seem to be any difference.
Note: In major version 1, the world is pre-built, in major version 2, the world is dynamically generated with a LuaVoxelManipulator. All versions use the singlenode mapgen.

Another probably important thing about Tutorial World is that it only consists of a castle-like structure but nothing else. There is no landscape etc.

I also have tried to use WorldEdit to move every node down by, I don't know, 26 node lengths or so. But this didn't help either.

So, here are my questions:

• What the hell is going on here?
• Why is everything green?
• Why does the radar show something sometimes but it quickly fades away again (and can't be restored/reproduced by returning)?
• How do I make the radar show what it is supposed to show, i.e. Tutorial World?
• Are there some radar tricks (like configuration variables) I could try out and play around with?
• How does the radar work, anyways (i.e. how does it “know” when to make areas black or green, etc.)?

Oh, if you want to test the tutorial, please use Tutorial version 2.0.1 (or later) for testing, if possible.

the radar shows the amount of air present. So areas with more air will be more green. The tutorial world is mostly air, so it will be mostly green.

But the thing is, it is fully (!) green. It is a big flat uniform green area which I see. There are not shades of darker green. I would assume that the greenness would be at least slightly darker for some structures. :-(
Well, sometimes I see darker green tones but for some reason they disappear as quickly as they came. It is not reproducible and the area will stay entirely green for the rest of this session, I suppose.
Because the radar only shows a 100% green screen most of the time, it is useless for tutorial purposes. :-(

By the way, is this really the whole “magic” behind the radar? Just counting the air nodes? Just out of curiosity, can I configure the radar to count nodes other than air?

Another probably important thing about Tutorial World is that it only consists of a castle-like structure but nothing else. There is no landscape etc.

Think of it as ground-penetrating radar - underground, the radar map is mostly black, with green areas indicating openness (caves).