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Generate biomes: Recalculate biome at biome lower limit

Prevents biome nodes passing below the defined y_min of that biome.
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paramat committed Sep 16, 2017
1 parent 808ada1 commit a1389c38658fe69c3bd25c3099bae9a4e51ed401
Showing with 9 additions and 18 deletions.
  1. +0 −10 doc/lua_api.txt
  2. +9 −8 src/mapgen.cpp
@@ -4630,9 +4630,6 @@ Definition tables

### Biome definition (`register_biome`)

**Note**
The Biome API is still in an experimental phase and subject to change.

{
name = "tundra",
node_dust = "default:snow",
@@ -4659,13 +4656,6 @@ The Biome API is still in an experimental phase and subject to change.
y_max = 31000,
-- ^ Lower and upper limits for biome.
-- ^ Limits are relative to y = water_level - 1.
-- ^ Because biome is not recalculated for every node in a node column
-- ^ some biome materials can exceed their limits, especially stone.
-- ^ For each node column in a mapchunk, biome is only recalculated at column
-- ^ top and at each of these surfaces:
-- ^ Ground below air, water below air, ground below water.
-- ^ The selected biome then stays in effect for all nodes below until
-- ^ column base or the next biome recalculation.
heat_point = 0,
humidity_point = 50,
-- ^ Characteristic average temperature and humidity for the biome.
@@ -633,6 +633,7 @@ void MapgenBasic::generateBiomes(MgStoneType *mgstone_type,
u16 base_filler = 0;
u16 depth_water_top = 0;
u16 depth_riverbed = 0;
s16 biome_y_min = -MAX_MAP_GENERATION_LIMIT;
u32 vi = vm->m_area.index(x, node_max.Y, z);

// Check node at base of mapchunk above, either a node of a previously
@@ -650,22 +651,20 @@ void MapgenBasic::generateBiomes(MgStoneType *mgstone_type,

for (s16 y = node_max.Y; y >= node_min.Y; y--) {
content_t c = vm->m_data[vi].getContent();

// Biome is recalculated each time an upper surface is detected while
// working down a column. The selected biome then remains in effect for
// all nodes below until the next surface and biome recalculation.
// Biome is recalculated:
// Biome is (re)calculated:
// 1. At the surface of stone below air or water.
// 2. At the surface of water below air.
// 3. When stone or water is detected but biome has not yet been calculated.
// 4. When stone or water is detected just below a biome's lower limit.
bool is_stone_surface = (c == c_stone) &&
(air_above || water_above || !biome);
(air_above || water_above || !biome || y < biome_y_min); // 1, 3, 4

bool is_water_surface =
(c == c_water_source || c == c_river_water_source) &&
(air_above || !biome);
(air_above || !biome || y < biome_y_min); // 2, 3, 4

if (is_stone_surface || is_water_surface) {
// (Re)calculate biome
// Limit to +-MAX MAP GENERATION LIMIT to work with biome y_min / y_max.
s32 relative_y = rangelim(y - biome_zero_level,
-MAX_MAP_GENERATION_LIMIT, MAX_MAP_GENERATION_LIMIT);
@@ -677,9 +676,11 @@ void MapgenBasic::generateBiomes(MgStoneType *mgstone_type,
depth_top = biome->depth_top;
base_filler = MYMAX(depth_top +
biome->depth_filler +
noise_filler_depth->result[index], 0.f);
noise_filler_depth->result[index], 0.0f);
depth_water_top = biome->depth_water_top;
depth_riverbed = biome->depth_riverbed;
biome_y_min = rangelim(biome->y_min + biome_zero_level,
-MAX_MAP_GENERATION_LIMIT, MAX_MAP_GENERATION_LIMIT);

// Detect stone type for dungeons during every biome calculation.
// If none detected the last selected biome stone is chosen.

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