Preventing caves from generating at surface level

[sorcerykid]

In mapgen v7 is there any way to prevent cave generation above a certain height, specifically to avoid large gaping holes in the terrain? I've struggled with this dilemma for quite some time, but have yet to find a solution. I've tweaked all of the relevant the noise parameters, yet certain caves seem to ignore both "mgv7_np_cave1" and "mgv7_np_cave2". I've searched Google the past two days, but there is very little technical documentation about customizing mapgen v7, just a lot of screenshots. What am I missing?

Any help or direction would be greatly appreciated.

[maikerumine]

Please paramat, help! The only way I found was to disable all cave generation, as well as rivers. It messes up the map. :(
Moreover, I forgot how to disable this.

[sorcerykid]

Thanks maikerumine. Indeed the only workaround I've found is to set mg_flags to "nocaves". But that undermines my goal, since I do want caves in my world. If only there was a cave_depth_min and cave_depth_max parameter to restrict the cave generation range.

[sorcerykid]

It seems I successfully devised an interim solution at least for Minetest 0.4.13, by reworking the following code in cavegen.cpp:

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Code: Select all

CaveV7::CaveV7(MapgenV7 *mg, PseudoRandom *ps)
{
        this->mg             = mg;
        this->vm             = mg->vm;
        this->ndef           = mg->ndef;
        this->water_level    = mg->water_level;
// SK fix begin
        this->surface_level  = mg->terrain_surface_level;
// SK fix end
:


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void CaveV7::makeCave(v3s16 nmin, v3s16 nmax, int max_stone_height) {
:
// SK fix begin
   // Allow tunnel radius to project above surface
   route_y_max = -of.Y + max_stone_y + max_tunnel_diameter / 2;

   // Limit maximum to area
   route_y_max = rangelim(route_y_max, 0, ar.Y - 1);
   // Limit maximum to area
   route_y_max = rangelim(route_y_max, 0, ar.Y - 1);

   s16 min = 0;
   if (node_min.Y < surface_level && node_max.Y > surface_level) {
      min = surface_level - max_tunnel_diameter/3 - of.Y;
      route_y_max = surface_level + max_tunnel_diameter/3 - of.Y;
   }
// SK fix end
:


I also defined "surface_level" and "terrain_surface_level" within the appropriate structs and classes of cavegen.h and mapgen.h. And, of course, I added "terrain_surface_level" to mapgen.cpp, as a user-definable parameter.

I was hoping to implement a "terrain_bedrock_level" as a counterpart to "terrain_surface_level" thereby setting the minimum cave generation range, but that would have required far more substantial changes to cavegen.cpp (as it stands, the upper limit was already conditional on "mg->water_level", so that was an easy enough replacement.) Since I'm fairly unfamiliar with the mapgen logic, I didn't venture much further for fear of breaking something important.

This of course is just a quick and dirty fix. Ideally there would be a formalized specification for cavegen parameters, maybe in a future release I hope :)

[paramat]

There are 2 types of cave in mgv7: the web of narrow tunnels, and the large blob-shaped caverns which sometimes have water or lava. The surface holes are mostly the tunnels, you can't limit these according to y but you can remove the tunnels without removing the large caverns, if this sounds good to you i'll tell you how.

[paramat]

Your code above only affects the large caves, not the tunnels.

[sorcerykid]

Hi paramat, I would be interested in learning more about any solutions you can suggest. I tested a number of different caves, including those with tunnels. Each time I reduced "terrain_surface_level", the depth of the caves would adjust accordingly and any non-conforming tunnels would disappear.

Trial #1: http://imgur.com/a/Z62Qt
Trial #2: http://imgur.com/a/mIsIC
Trial #3: http://imgur.com/a/Z0vLs

Perhaps I'm missing something, but each of the test cases above worked. On a sidenote, I overlooked these two snippets of code that I changed as well in cavegen.cpp.

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void CaveV7::makeTunnel(bool dirswitch) {
:
} else if (p.Y > surface_level) {
      return; // If it's not in our heightmap, use a simple heuristic
}
:
} else if (p.Y > surface_level) {
      return;
}


[paramat]

0.4.13 has these 3D noise tunnels https://github.com/minetest/minetest/blob/0.4.13/src/mapgen_v7.cpp#L864
But you can easily limit those on a per-mapchunk basis in line 861.

[sorcerykid]

Thanks for the tip paramat. I can see from mapgen_v7.cpp that the tunnels can only be limited on a per-mapchunk basis.

However, am I to understand correctly that while the function "generateCaves( )" creates the tunnels, the function "makeTunnel( )" is what actually creates the caverns? Isn't that backwards? O_o

[paramat]

In non-mgv6 mapgens generateCaves() creates the 3D noise tunnels and also the classic large caves from mgv6.

makeTunnel() was named for mgv6 where that code creates both the large caverns and the smaller tunnels by varying the width, both are essentially tunnels because they are a string of excavated volumes.