Make humidity ignore ocean chunks.

world/src/sim/mod.rs

@@ -132,10 +132,26 @@ impl WorldSim {
                 .set_seed(gen_seed()),
         };
 
-        // From 0 to 1.6, but the distribution before the max is from -1 and 1, so there is a 50%
-        // chance that hill will end up at 0.
-        let hill = uniform_noise(|_, wposf| {
-            (0.0 + gen_ctx
+        // "Base" of the chunk, to be multiplied by CONFIG.mountain_scale (multiplied value is
+        // from -0.25 * (CONFIG.mountain_scale * 1.1) to 0.25 * (CONFIG.mountain_scale * 0.9),
+        // but value here is from -0.275 to 0.225).
+        let alt_base = uniform_noise(|_, wposf| {
+            Some((gen_ctx.alt_nz.get((wposf.div(12_000.0)).into_array()) as f32)
+                .sub(0.1)
+                .mul(0.25))
+        });
+
+        // -1 to 1.
+        let temp_base = uniform_noise(|_, wposf| {
+            Some((gen_ctx.temp_nz.get((wposf.div(12000.0)).into_array()) as f32))
+        });
+
+        // chaos produces a value in [0.1, 1.24].  It is a meta-level factor intended to reflect how
+        // "chaotic" the region is--how much weird stuff is going on on this terrain.
+        let chaos = uniform_noise(|posi, wposf| {
+            // From 0 to 1.6, but the distribution before the max is from -1 and 1, so there is a
+            // 50% chance that hill will end up at 0.
+            let hill = (0.0 + gen_ctx
                 .hill_nz
                 .get((wposf.div(1_500.0)).into_array())
                 .mul(1.0) as f32
@@ -144,34 +160,9 @@ impl WorldSim {
                     .get((wposf.div(400.0)).into_array())
                     .mul(0.3) as f32)
                 .add(0.3)
-                .max(0.0)
-        });
+                .max(0.0);
 
-        // 0 to 1, hopefully.
-        let humid_base = uniform_noise(|_, wposf| {
-            (gen_ctx.humid_nz.get(wposf.div(1024.0).into_array()) as f32)
-                .add(1.0)
-                .mul(0.5)
-        });
-
-        // -1 to 1.
-        let temp_base = uniform_noise(|_, wposf| {
-            (gen_ctx.temp_nz.get((wposf.div(12000.0)).into_array()) as f32)
-        });
-
-        // "Base" of the chunk, to be multiplied by CONFIG.mountain_scale (multiplied value is
-        // from -0.25 * (CONFIG.mountain_scale * 1.1) to 0.25 * (CONFIG.mountain_scale * 0.9),
-        // but value here is from -0.275 to 0.225).
-        let alt_base = uniform_noise(|_, wposf| {
-            (gen_ctx.alt_nz.get((wposf.div(12_000.0)).into_array()) as f32)
-                .sub(0.1)
-                .mul(0.25)
-        });
-
-        // chaos produces a value in [0.1, 1.24].  It is a meta-level factor intended to reflect how
-        // "chaotic" the region is--how much weird stuff is going on on this terrain.
-        let chaos = uniform_noise(|posi, wposf| {
-            (gen_ctx.chaos_nz.get((wposf.div(3_000.0)).into_array()) as f32)
+            Some((gen_ctx.chaos_nz.get((wposf.div(3_000.0)).into_array()) as f32)
                 .add(1.0)
                 .mul(0.5)
                 // [0, 1] * [0.25, 1] = [0, 1] (but probably towards the lower end)
@@ -184,7 +175,7 @@ impl WorldSim {
                 // Chaos is always increased by a little when we're on a hill (but remember that
                 // hill is 0 about 50% of the time).
                 // [0, 1] + 0.15 * [0, 1.6] = [0, 1.24]
-                .add(0.2 * hill[posi].1)
+                .add(0.2 * hill)
                 // [0, 1.24] * [0.35, 1.0] = [0, 1.24].
                 // Sharply decreases (towards 0.35) when temperature is near desert_temp (from below),
                 // then saturates just before it actually becomes desert.  Otherwise stays at 1.
@@ -200,7 +191,7 @@ impl WorldSim {
                         .min(1.0),
                 )
                 // We can't have *no* chaos!
-                .max(0.1)
+                .max(0.1))
         });
 
         // We ignore sea level because we actually want to be relative to sea level here and want
@@ -227,9 +218,9 @@ impl WorldSim {
                 (0.0 + alt_main
                     + (gen_ctx.small_nz.get((wposf.div(300.0)).into_array()) as f32)
                         .mul(alt_main.max(0.25))
-                        .mul(0.3))
+                        .mul(0.3)
                 .add(1.0)
-                .mul(0.5)
+                .mul(0.5))
             };
 
             // Now we can compute the final altitude using chaos.
@@ -237,7 +228,18 @@ impl WorldSim {
             // alt_pre, then multiply by CONFIG.mountain_scale and add to the base and sea level to
             // get an adjusted value, then multiply the whole thing by map_edge_factor
             // (TODO: compute final bounds).
-            (alt_base[posi].1 + alt_main.mul(chaos[posi].1)).mul(map_edge_factor(posi))
+            Some((alt_base[posi].1 + alt_main.mul(chaos[posi].1)).mul(map_edge_factor(posi)))
+        });
+
+        // 0 to 1, hopefully.
+        let humid_base = uniform_noise(|posi, wposf| {
+            if alt[posi].1 <= 5.0.div(CONFIG.mountain_scale) {
+                None
+            } else {
+                Some((gen_ctx.humid_nz.get(wposf.div(1024.0).into_array()) as f32)
+                .add(1.0)
+                .mul(0.5))
+            }
         });
 
         let gen_cdf = GenCdf {

world/src/sim/util.rs

@@ -123,36 +123,37 @@ pub fn uniform_idx_as_vec2(idx: usize) -> Vec2<i32> {
 /// vector returned by uniform_noise, and (for convenience) the float-translated version of those
 /// coordinates.
 /// f should return a value with no NaNs.  If there is a NaN, it will panic.  There are no other
-/// conditions on f.
+/// conditions on f.  If f returns None, the value will be set to 0.0, and will be ignored for the
+/// purposes of computing the uniform range.
 ///
 /// Returns a vec of (f32, f32) pairs consisting of the percentage of chunks with a value lower than
 /// this one, and the actual noise value (we don't need to cache it, but it makes ensuring that
 /// subsequent code that needs the noise value actually uses the same one we were using here
 /// easier).
-pub fn uniform_noise(f: impl Fn(usize, Vec2<f64>) -> f32) -> InverseCdf {
+pub fn uniform_noise(f: impl Fn(usize, Vec2<f64>) -> Option<f32>) -> InverseCdf {
     let mut noise = (0..WORLD_SIZE.x * WORLD_SIZE.y)
-        .map(|i| {
+        .filter_map(|i| {
             (
-                i,
                 f(
                     i,
                     (uniform_idx_as_vec2(i) * TerrainChunkSize::SIZE.map(|e| e as i32))
                         .map(|e| e as f64),
-                ),
+                ).map(|res| (i, res))
             )
         })
         .collect::<Vec<_>>();
 
-    // sort_unstable_by is equivalent to sort_by here since we include the index in the
+    // sort_unstable_by is equivalent to sort_by here since we include a unique index in the
     // comparison.  We could leave out the index, but this might make the order not
     // reproduce the same way between different versions of Rust (for example).
     noise.sort_unstable_by(|f, g| (f.1, f.0).partial_cmp(&(g.1, g.0)).unwrap());
 
     // Construct a vector that associates each chunk position with the 1-indexed
     // position of the noise in the sorted vector (divided by the vector length).
-    // This guarantees a uniform distribution among the samples.
+    // This guarantees a uniform distribution among the samples (excluding those that returned
+    // None, which will remain at zero).
     let mut uniform_noise = vec![(0.0, 0.0); WORLD_SIZE.x * WORLD_SIZE.y].into_boxed_slice();
-    let total = (WORLD_SIZE.x * WORLD_SIZE.y) as f32;
+    let total = noise.len() as f32;
     for (noise_idx, (chunk_idx, noise_val)) in noise.into_iter().enumerate() {
         uniform_noise[chunk_idx] = ((1 + noise_idx) as f32 / total, noise_val);
     }