Mapgen: Optimise cave noises and tunnel excavation

[oweals/minetest.git] / src / mapgen_flat.cpp

diff --git a/src/mapgen_flat.cpp b/src/mapgen_flat.cpp
index 0d071411d75a5a376511804c90e035f656003ffa..ecfbe49ba4d51360feb0ff1d684e0d7e8ac0f839 100644 (file)
--- a/src/mapgen_flat.cpp
+++ b/src/mapgen_flat.cpp
@@ -58,7 +58,8 @@ MapgenFlat::MapgenFlat(int mapgenid, MapgenParams *params, EmergeManager *emerge
        //// amount of elements to skip for the next index
        //// for noise/height/biome maps (not vmanip)
        this->ystride = csize.X;
-       this->zstride = csize.X * (csize.Y + 2);
+       // 1-down overgeneration
+       this->zstride_1d = csize.X * (csize.Y + 1);
 
        this->biomemap        = new u8[csize.X * csize.Z];
        this->heightmap       = new s16[csize.X * csize.Z];
@@ -80,8 +81,9 @@ MapgenFlat::MapgenFlat(int mapgenid, MapgenParams *params, EmergeManager *emerge
        noise_filler_depth = new Noise(&sp->np_filler_depth, seed, csize.X, csize.Z);
 
        //// 3D noise
-       noise_cave1 = new Noise(&sp->np_cave1, seed, csize.X, csize.Y + 2, csize.Z);
-       noise_cave2 = new Noise(&sp->np_cave2, seed, csize.X, csize.Y + 2, csize.Z);
+       // 1-down overgeneraion
+       noise_cave1 = new Noise(&sp->np_cave1, seed, csize.X, csize.Y + 1, csize.Z);
+       noise_cave2 = new Noise(&sp->np_cave2, seed, csize.X, csize.Y + 1, csize.Z);
 
        //// Biome noise
        noise_heat           = new Noise(&params->np_biome_heat,           seed, csize.X, csize.Z);
@@ -565,14 +567,21 @@ void MapgenFlat::generateCaves(s16 max_stone_y)
        for (s16 z = node_min.Z; z <= node_max.Z; z++)
        for (s16 x = node_min.X; x <= node_max.X; x++, index2d++) {
                bool column_is_open = false;  // Is column open to overground
-               u32 vi = vm->m_area.index(x, node_max.Y + 1, z);
-               u32 index3d = (z - node_min.Z) * zstride + (csize.Y + 1) * ystride +
+               bool is_tunnel = false;  // Is tunnel or tunnel floor
+               u32 vi = vm->m_area.index(x, node_max.Y, z);
+               u32 index3d = (z - node_min.Z) * zstride_1d + csize.Y * ystride +
                        (x - node_min.X);
                // Biome of column
                Biome *biome = (Biome *)bmgr->getRaw(biomemap[index2d]);
 
-               for (s16 y = node_max.Y + 1; y >= node_min.Y - 1;
-                               y--, index3d -= ystride, vm->m_area.add_y(em, vi, -1)) {
+               // Don't excavate the overgenerated stone at node_max.Y + 1,
+               // this creates a 'roof' over the tunnel, preventing light in
+               // tunnels at mapchunk borders when generating mapchunks upwards.
+               // This 'roof' is removed when the mapchunk above is generated.
+               for (s16 y = node_max.Y; y >= node_min.Y - 1; y--,
+                               index3d -= ystride,
+                               vm->m_area.add_y(em, vi, -1)) {
+
                        content_t c = vm->m_data[vi].getContent();
                        if (c == CONTENT_AIR || c == biome->c_water_top ||
                                        c == biome->c_water) {
@@ -585,13 +594,16 @@ void MapgenFlat::generateCaves(s16 max_stone_y)
                        if (d1 * d2 > 0.3f && ndef->get(c).is_ground_content) {
                                // In tunnel and ground content, excavate
                                vm->m_data[vi] = MapNode(CONTENT_AIR);
-                       } else if (column_is_open &&
+                               is_tunnel = true;
+                       } else if (is_tunnel && column_is_open &&
                                        (c == biome->c_filler || c == biome->c_stone)) {
                                // Tunnel entrance floor
                                vm->m_data[vi] = MapNode(biome->c_top);
                                column_is_open = false;
+                               is_tunnel = false;
                        } else {
                                column_is_open = false;
+                               is_tunnel = false;
                        }
                }
        }