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Merged
github-actions merged 1 commit into from
May 2, 2026
Merged

feat: apply biome terrain modifiers #669

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100 changes: 89 additions & 11 deletions modules/world-worldgen/src/height_sampler.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ const ColumnNoiseValues = noise_sampler_mod.ColumnNoiseValues;
const region_pkg = @import("region.zig");
const PathInfo = region_pkg.PathInfo;
const RegionControls = region_pkg.RegionControls;
const TerrainModifier = @import("biome_registry.zig").TerrainModifier;
const world_class = @import("world_class.zig");
const ContinentalZone = world_class.ContinentalZone;

Expand Down Expand Up @@ -195,6 +196,17 @@ pub const HeightSampler = struct {
return std.math.lerp(base_modulated, alt_modulated, blend) * mood_mult;
}

fn applyPeakCompression(self: *const HeightSampler, height: f32) f32 {
const p = self.params;
const sea: f32 = @floatFromInt(p.sea_level);
const peak_start = sea + p.peak_compression_offset;
if (height <= peak_start) return height;

const h_above = height - peak_start;
const compressed = p.peak_compression_range * (1.0 - std.math.exp(-h_above / p.peak_compression_range));
return peak_start + compressed;
}

/// STRUCTURE-FIRST height computation with V7-style multi-layer terrain.
///
/// The KEY change: Ocean is decided by continentalness ALONE.
Expand All @@ -212,6 +224,18 @@ pub const HeightSampler = struct {
controls: RegionControls,
path_info: PathInfo,
reduction: u8,
) f32 {
return self.computeHeightWithTerrainModifier(noise_sampler, noise, controls, path_info, reduction, null);
}

pub fn computeHeightWithTerrainModifier(
self: *const HeightSampler,
noise_sampler: *const NoiseSampler,
noise: ColumnNoiseValues,
controls: RegionControls,
path_info: PathInfo,
reduction: u8,
terrain_modifier: ?TerrainModifier,
) f32 {
// Validate reduction is in expected range (0-4 for LOD0-LOD3)
std.debug.assert(reduction <= 4);
Expand Down Expand Up @@ -290,12 +314,10 @@ pub const HeightSampler = struct {
// ============================================================
// STEP 7: Post-Processing - Peak compression
// ============================================================
const peak_start = sea + p.peak_compression_offset;
if (height > peak_start) {
const h_above = height - peak_start;
const compressed = p.peak_compression_range * (1.0 - std.math.exp(-h_above / p.peak_compression_range));
height = peak_start + compressed;
if (terrain_modifier) |modifier| {
height = modifier.applyHeight(height, sea);
}
height = self.applyPeakCompression(height);

// ============================================================
// STEP 8: River Carving - REGION-CONSTRAINED
Expand Down Expand Up @@ -344,12 +366,7 @@ pub const HeightSampler = struct {
}

// Peak compression
const peak_start = sea + p.peak_compression_offset;
if (height > peak_start) {
const h_above = height - peak_start;
const compressed = p.peak_compression_range * (1.0 - std.math.exp(-h_above / p.peak_compression_range));
height = peak_start + compressed;
}
height = self.applyPeakCompression(height);

return height;
}
Expand Down Expand Up @@ -400,3 +417,64 @@ test "HeightSampler mountain mask range" {
const m2 = sampler.getMountainMask(0.2, 0.8, 0.4);
try std.testing.expect(m2 >= 0.0 and m2 <= 1.0);
}

fn testNoiseValues(continentalness: f32, terrain: f32) ColumnNoiseValues {
return .{
.warp = .{ .x = 0.0, .z = 0.0 },
.warped_x = 128.0,
.warped_z = 256.0,
.continentalness = continentalness,
.erosion = 0.5,
.peaks_valleys = 0.75,
.temperature = 0.5,
.humidity = 0.5,
.river_mask = 0.0,
.terrain_base = terrain,
.terrain_alt = terrain,
.height_select = 0.0,
.terrain_persist = 1.0,
.variant = 0.0,
};
}

const test_controls = RegionControls{
.height_mult = 1.0,
.vegetation_mult = 1.0,
.drama_mask = 0.0,
.river_mask = 0.0,
.subbiome_mask = 0.0,
};

const test_path = PathInfo{
.path_type = .none,
.influence = 0.0,
.direction = .{ 0.0, 0.0 },
};

test "HeightSampler applies biome terrain modifiers to land height" {
const sampler = HeightSampler.init();
const noise_sampler = NoiseSampler.init(1234);
const noise = testNoiseValues(0.55, 20.0);
const sea = sampler.getSeaLevelFloat();

const base = sampler.computeHeight(&noise_sampler, noise, test_controls, test_path, 0);
const flattened = sampler.computeHeightWithTerrainModifier(&noise_sampler, noise, test_controls, test_path, 0, .{ .smoothing = 1.0 });
const amplified = sampler.computeHeightWithTerrainModifier(&noise_sampler, noise, test_controls, test_path, 0, .{ .height_amplitude = 1.25 });
const clamped = sampler.computeHeightWithTerrainModifier(&noise_sampler, noise, test_controls, test_path, 0, .{ .clamp_to_sea_level = true, .height_offset = -2.0 });

try std.testing.expect(base > sea);
try std.testing.expectApproxEqAbs(sea, flattened, 0.0001);
try std.testing.expect(amplified > base);
try std.testing.expectApproxEqAbs(sea - 2.0, clamped, 0.0001);
}

test "HeightSampler applies peak compression after terrain amplification" {
const sampler = HeightSampler.init();
const noise_sampler = NoiseSampler.init(5678);
const noise = testNoiseValues(0.9, 300.0);
const peak_limit = sampler.getSeaLevelFloat() + sampler.params.peak_compression_offset + sampler.params.peak_compression_range;

const amplified = sampler.computeHeightWithTerrainModifier(&noise_sampler, noise, test_controls, test_path, 0, .{ .height_amplitude = 2.0 });

try std.testing.expect(amplified < peak_limit);
}
92 changes: 74 additions & 18 deletions modules/world-worldgen/src/terrain_shape_generator.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -140,6 +140,20 @@ pub const TerrainShapeGenerator = struct {
}

pub fn sampleColumnDataWithControls(self: *const TerrainShapeGenerator, wx: f32, wz: f32, reduction: u8, controls: region_pkg.RegionControls) ColumnData {
const base_column = self.sampleColumnDataWithControlsAndTerrainModifier(wx, wz, reduction, controls, null);
const preliminary_biome = self.selectBiomeForColumn(base_column, 1);
const biome_def = biome_mod.getBiomeDefinition(preliminary_biome);
return self.sampleColumnDataWithControlsAndTerrainModifier(wx, wz, reduction, controls, biome_def.terrain);
}

fn sampleColumnDataWithControlsAndTerrainModifier(
self: *const TerrainShapeGenerator,
wx: f32,
wz: f32,
reduction: u8,
controls: region_pkg.RegionControls,
terrain_modifier: ?biome_mod.TerrainModifier,
) ColumnData {
const sea: f32 = @floatFromInt(self.params.sea_level);
var noise = self.noise_sampler.sampleColumn(wx, wz, reduction);
const cj_octaves: u16 = if (2 > reduction) 2 - @as(u16, reduction) else 1;
Expand All @@ -153,7 +167,7 @@ pub const TerrainShapeGenerator = struct {
const wz_i: i32 = @intFromFloat(@floor(wz));
const region = region_pkg.getRegion(region_seed, wx_i, wz_i);
const path_info = region_pkg.getPathInfo(region_seed, wx_i, wz_i, region);
const terrain_height = self.height_sampler.computeHeight(&self.noise_sampler, noise, controls, path_info, reduction);
const terrain_height = self.height_sampler.computeHeightWithTerrainModifier(&self.noise_sampler, noise, controls, path_info, reduction, terrain_modifier);
const terrain_height_i: i32 = @intFromFloat(terrain_height);

const altitude_offset: f32 = @max(0, terrain_height - sea);
Expand Down Expand Up @@ -182,6 +196,24 @@ pub const TerrainShapeGenerator = struct {
};
}

fn selectBiomeForColumn(self: *const TerrainShapeGenerator, column: ColumnData, slope: i32) BiomeId {
const climate = self.biome_source.computeClimate(
column.temperature,
column.humidity,
column.terrain_height_i,
column.continentalness,
column.erosion,
CHUNK_SIZE_Y,
);
const structural = biome_mod.StructuralParams{
.height = column.terrain_height_i,
.slope = slope,
.continentalness = column.continentalness,
.ridge_mask = column.ridge_mask,
};
return self.biome_source.selectBiome(climate, structural, column.river_mask);
}

pub fn prepareChunkPhaseData(
self: *const TerrainShapeGenerator,
phase_data: *ChunkPhaseData,
Expand Down Expand Up @@ -209,7 +241,7 @@ pub const TerrainShapeGenerator = struct {
const wz_i = world_z + @as(i32, @intCast(local_z));
const wx: f32 = @floatFromInt(wx_i);
const wz: f32 = @floatFromInt(wz_i);
const column = self.sampleColumnDataWithControls(wx, wz, 0, controls.sample(wx_i, wz_i));
const column = self.sampleColumnDataWithControlsAndTerrainModifier(wx, wz, 0, controls.sample(wx_i, wz_i), null);

phase_data.surface_heights[idx] = column.terrain_height_i;
phase_data.is_underwater_flags[idx] = column.is_underwater;
Expand Down Expand Up @@ -266,6 +298,43 @@ pub const TerrainShapeGenerator = struct {
phase_data.biome_ids[idx] = biome_id;
phase_data.secondary_biome_ids[idx] = biome_id;
phase_data.biome_blends[idx] = 0.0;

const biome_def = biome_mod.getBiomeDefinition(biome_id);
const wx_i = world_x + @as(i32, @intCast(local_x));
const wz_i = world_z + @as(i32, @intCast(local_z));
const column = self.sampleColumnDataWithControlsAndTerrainModifier(
@floatFromInt(wx_i),
@floatFromInt(wz_i),
0,
controls.sample(wx_i, wz_i),
biome_def.terrain,
);
phase_data.surface_heights[idx] = column.terrain_height_i;
phase_data.is_underwater_flags[idx] = column.is_underwater;
phase_data.is_ocean_water_flags[idx] = column.is_ocean;
phase_data.cave_region_values[idx] = column.cave_region;
phase_data.temperatures[idx] = column.temperature;
phase_data.humidities[idx] = column.humidity;
phase_data.continentalness_values[idx] = column.continentalness;
phase_data.erosion_values[idx] = column.erosion;
phase_data.ridge_masks[idx] = column.ridge_mask;
phase_data.river_masks[idx] = column.river_mask;
}
}

local_z = 0;
while (local_z < CHUNK_SIZE_Z) : (local_z += 1) {
if (stop_flag) |sf| if (sf.*) return false;
var local_x: u32 = 0;
while (local_x < CHUNK_SIZE_X) : (local_x += 1) {
const idx = local_x + local_z * CHUNK_SIZE_X;
const terrain_h = phase_data.surface_heights[idx];
var max_slope: i32 = 0;
if (local_x > 0) max_slope = @max(max_slope, @as(i32, @intCast(@abs(terrain_h - phase_data.surface_heights[idx - 1]))));
if (local_x < CHUNK_SIZE_X - 1) max_slope = @max(max_slope, @as(i32, @intCast(@abs(terrain_h - phase_data.surface_heights[idx + 1]))));
if (local_z > 0) max_slope = @max(max_slope, @as(i32, @intCast(@abs(terrain_h - phase_data.surface_heights[idx - CHUNK_SIZE_X]))));
if (local_z < CHUNK_SIZE_Z - 1) max_slope = @max(max_slope, @as(i32, @intCast(@abs(terrain_h - phase_data.surface_heights[idx + CHUNK_SIZE_X]))));
phase_data.slopes[idx] = max_slope;
}
}

Expand Down Expand Up @@ -404,22 +473,9 @@ pub const TerrainShapeGenerator = struct {
pub fn sampleBiomeAtWorld(self: *const TerrainShapeGenerator, wx: i32, wz: i32) BiomeId {
const wxf: f32 = @floatFromInt(wx);
const wzf: f32 = @floatFromInt(wz);
const column = self.sampleColumnData(wxf, wzf, 0);
const climate = self.biome_source.computeClimate(
column.temperature,
column.humidity,
column.terrain_height_i,
column.continentalness,
column.erosion,
CHUNK_SIZE_Y,
);
const structural = biome_mod.StructuralParams{
.height = column.terrain_height_i,
.slope = 1,
.continentalness = column.continentalness,
.ridge_mask = column.ridge_mask,
};
return self.biome_source.selectBiome(climate, structural, column.river_mask);
const controls = region_pkg.getBlendedControls(self.getRegionSeed(), wx, wz);
const column = self.sampleColumnDataWithControlsAndTerrainModifier(wxf, wzf, 0, controls, null);
return self.selectBiomeForColumn(column, 1);
}

pub fn detectBiomeEdge(
Expand Down
4 changes: 2 additions & 2 deletions src/worldgen_tests.zig
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -218,9 +218,9 @@ test "WorldGen stable chunk fingerprints for known seed" {
};

const expected = [_]u64{
16067496184749289293,
1589085686761579315,
10106071382427144696,
12094872152942993063,
12283863255206387139,
};

for (positions, 0..) |pos, i| {
Expand Down
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