Tooling

Tools/Terrain/internal/planet/output_test.go

@@ -0,0 +1,54 @@
+package planet
+
+import (
+	"math"
+	"testing"
+)
+
+// boxDown is what the two overview heightmaps are made with, and a planet's two sides rarely share an
+// integer factor, so it has to be right at a ratio that does not divide.
+func TestBoxDownAveragesAndKeepsTheMean(t *testing.T) {
+	const w, h = 12, 7
+	src := make([]float32, w*h)
+	sum := 0.0
+	for i := range src {
+		src[i] = float32(i%5) + float32(i/w)
+		sum += float64(src[i])
+	}
+	want := sum / float64(len(src))
+
+	for _, d := range [][2]int{{6, 7}, {4, 3}, {5, 3}, {12, 7}, {1, 1}} {
+		out := boxDown(src, w, h, d[0], d[1])
+		if len(out) != d[0]*d[1] {
+			t.Fatalf("%dx%d: got %d values", d[0], d[1], len(out))
+		}
+		got := 0.0
+		for _, v := range out {
+			got += float64(v)
+		}
+		got /= float64(len(out))
+		// Buckets do not all hold the same number of cells at a ratio that does not divide, so the mean of
+		// the means drifts a little; what must not happen is a bucket left empty or a value invented.
+		if math.Abs(got-want) > 0.35 {
+			t.Errorf("%dx%d: mean %.3f, source mean %.3f", d[0], d[1], got, want)
+		}
+		lo, hi := math.Inf(1), math.Inf(-1)
+		for _, v := range out {
+			lo = math.Min(lo, float64(v))
+			hi = math.Max(hi, float64(v))
+		}
+		if lo < 0 || hi > 11 {
+			t.Errorf("%dx%d: range %.2f..%.2f is outside the source's 0..10", d[0], d[1], lo, hi)
+		}
+	}
+}
+
+func TestBoxDownIsIdentityAtTheSameSize(t *testing.T) {
+	src := []float32{1, 2, 3, 4, 5, 6}
+	out := boxDown(src, 3, 2, 3, 2)
+	for i := range src {
+		if out[i] != src[i] {
+			t.Fatalf("cell %d: %v, want %v", i, out[i], src[i])
+		}
+	}
+}