diff --git a/internal/world/placed_features.go b/internal/world/placed_features.go
index 667e785..3dc2114 100644
--- a/internal/world/placed_features.go
+++ b/internal/world/placed_features.go
@@ -106,24 +106,25 @@ func flattenBlockTag(set *worldgen.FeatureSet, tag string, visiting map[string]b
 }
 
 func placeOreEllipsoid(c *Chunk, random worldgen.RandomSource, originX, originY, originZ, size int, discard float64, targets []resolvedOreTarget) {
-	angle := float64(random.NextFloat()) * math.Pi
-	extent := float64(size) / 8.0
-	x0 := float64(originX) + math.Sin(angle)*extent
-	x1 := float64(originX) - math.Sin(angle)*extent
-	z0 := float64(originZ) + math.Cos(angle)*extent
-	z1 := float64(originZ) - math.Cos(angle)*extent
+	angle := random.NextFloat() * float32(math.Pi)
+	extent := float32(size) / 8.0
+	x0 := float64(originX) + math.Sin(float64(angle))*float64(extent)
+	x1 := float64(originX) - math.Sin(float64(angle))*float64(extent)
+	z0 := float64(originZ) + math.Cos(float64(angle))*float64(extent)
+	z1 := float64(originZ) - math.Cos(float64(angle))*float64(extent)
 	y0 := float64(originY + int(random.NextIntN(3)) - 2)
 	y1 := float64(originY + int(random.NextIntN(3)) - 2)
 
 	type sphere struct{ x, y, z, radius float64 }
 	spheres := make([]sphere, size)
 	for i := 0; i < size; i++ {
-		t := float64(i) / float64(size)
-		radius := (math.Sin(math.Pi*t) + 1.0) * (float64(random.NextDouble())*float64(size)/16.0 + 1.0) / 2.0
+		t := float32(i) / float32(size)
+		randomScale := random.NextDouble() * float64(size) / 16.0
+		radius := ((float64(worldgen.MthSin(float64(float32(math.Pi)*t)))+1.0)*randomScale + 1.0) / 2.0
 		spheres[i] = sphere{
-			x:      x0 + (x1-x0)*t,
-			y:      y0 + (y1-y0)*t,
-			z:      z0 + (z1-z0)*t,
+			x:      x0 + (x1-x0)*float64(t),
+			y:      y0 + (y1-y0)*float64(t),
+			z:      z0 + (z1-z0)*float64(t),
 			radius: radius,
 		}
 	}
diff --git a/internal/world/store.go b/internal/world/store.go
index 377865a..4b40489 100644
--- a/internal/world/store.go
+++ b/internal/world/store.go
@@ -33,7 +33,7 @@ const dataVersion26 = 4790
 // first time it ran: chunkAt prefers the store over the generator, so the
 // already-explored area around spawn keeps its old terrain and every later fix
 // looks like it did nothing in exactly the place you are standing.
-const generatorVersion = 16
+const generatorVersion = 17
 
 // generatorVersionTag is the NBT key holding generatorVersion. It is namespaced
 // because it is ours, not part of the vanilla chunk format.
diff --git a/internal/world/vanilla_parity_test.go b/internal/world/vanilla_parity_test.go
index a146f91..d2cd8c4 100644
--- a/internal/world/vanilla_parity_test.go
+++ b/internal/world/vanilla_parity_test.go
@@ -129,7 +129,7 @@ func TestVanillaBlockParity(t *testing.T) {
 	// The ordinary CI profile is a regression floor while the port is still
 	// incomplete. REGIONIO_REQUIRE_PARITY upgrades the same exhaustive audit to
 	// exact equality; there is no sampled or summary-only comparison path.
-	if percent(blockExact, blockTotal) < 90 || biomeExact != biomeTotal || heightExact != heightTotal {
+	if percent(blockExact, blockTotal) < 91 || biomeExact != biomeTotal || heightExact != heightTotal {
 		t.Fatalf("vanilla parity regressed below the committed baseline")
 	}
 	if os.Getenv("REGIONIO_REQUIRE_PARITY") == "1" && (blockExact != blockTotal || biomeExact != biomeTotal || heightExact != heightTotal) {