feat(render): implement Campaign AR and terrain fidelity

tests/AcDream.App.Tests/Rendering/Packs/AtmosphericGpuTimerSamplingTests.cs

@@ -0,0 +1,63 @@
+using AcDream.App.Rendering.Packs;
+using AcDream.Plugin.Abstractions.Rendering;
+
+namespace AcDream.App.Tests.Rendering.Packs;
+
+public sealed class AtmosphericGpuTimerSamplingTests
+{
+    [Fact]
+    public void LowMeasuresOneCompleteFrameInFour()
+    {
+        bool[] measured = Enumerable.Range(1, 12)
+            .Select(frame => AtmosphericGpuTimerSampling.ShouldMeasure(
+                RenderQualitySemantic.Low,
+                frame))
+            .ToArray();
+
+        Assert.Equal(
+            [false, false, false, true, false, false, false, true, false, false, false, true],
+            measured);
+    }
+
+    [Theory]
+    [InlineData(RenderQualitySemantic.Medium)]
+    [InlineData(RenderQualitySemantic.High)]
+    public void OtherQualitiesMeasureEveryFrame(RenderQualitySemantic quality)
+    {
+        for (long frame = 1; frame <= 32; frame++)
+            Assert.True(AtmosphericGpuTimerSampling.ShouldMeasure(quality, frame));
+    }
+
+    [Fact]
+    public void RejectsNonPositiveFrameSerial()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+            AtmosphericGpuTimerSampling.ShouldMeasure(
+                RenderQualitySemantic.Low,
+                frameSerial: 0));
+    }
+
+    [Fact]
+    public void WarmSamplingDecisionsAllocateZero()
+    {
+        _ = AtmosphericGpuTimerSampling.ShouldMeasure(
+            RenderQualitySemantic.Low,
+            frameSerial: 1);
+
+        int measured = 0;
+        long before = GC.GetAllocatedBytesForCurrentThread();
+        for (long frame = 1; frame <= 10_000; frame++)
+        {
+            if (AtmosphericGpuTimerSampling.ShouldMeasure(
+                    RenderQualitySemantic.Low,
+                    frame))
+            {
+                measured++;
+            }
+        }
+        long allocated = GC.GetAllocatedBytesForCurrentThread() - before;
+
+        Assert.Equal(2_500, measured);
+        Assert.Equal(0, allocated);
+    }
+}