feat(render): implement Campaign AR and terrain fidelity

tests/AcDream.App.Tests/Rendering/Wb/DirectionalShadowTerrainPreparedDrawTests.cs

@@ -0,0 +1,75 @@
+using AcDream.App.Rendering;
+
+namespace AcDream.App.Tests.Rendering.Wb;
+
+public sealed class DirectionalShadowTerrainPreparedDrawTests
+{
+    [Fact]
+    public void Product_ContainsEveryResidentRangeWithoutVisibilityClassification()
+    {
+        var product = new DirectionalShadowTerrainPreparedDraws();
+        Assert.True(product.TryBegin(frameSequence: 10, estimatedCommands: 3));
+        DirectionalShadowTerrainRange[] resident =
+        [
+            new(FirstIndex: 0, IndexCount: 384),
+            new(FirstIndex: 384, IndexCount: 384),
+            new(FirstIndex: 768, IndexCount: 384),
+        ];
+        foreach (DirectionalShadowTerrainRange range in resident)
+            product.Add(in range);
+
+        product.Complete(frameSequence: 10);
+
+        Assert.Equal(3, product.Commands.Length);
+        Assert.Equal(0u, product.Commands[0].FirstIndex);
+        Assert.Equal(384u, product.Commands[1].FirstIndex);
+        Assert.Equal(768u, product.Commands[2].FirstIndex);
+        Assert.All(
+            product.Commands.ToArray(),
+            static command =>
+            {
+                Assert.Equal(384u, command.Count);
+                Assert.Equal(1u, command.InstanceCount);
+                Assert.Equal(0, command.BaseVertex);
+            });
+    }
+
+    [Fact]
+    public void SameFrame_AllCascadesReuseOneTerrainBuild()
+    {
+        var product = new DirectionalShadowTerrainPreparedDraws();
+        Assert.True(product.TryBegin(frameSequence: 1, estimatedCommands: 1));
+        var range = new DirectionalShadowTerrainRange(100, 24);
+        product.Add(in range);
+        product.Complete(frameSequence: 1);
+        long retained = product.RetainedScratchBytes;
+
+        Assert.False(product.TryBegin(frameSequence: 1, estimatedCommands: 500));
+
+        Assert.Equal(1ul, product.BuildSequence);
+        Assert.Equal(retained, product.RetainedScratchBytes);
+        Assert.Single(product.Commands.ToArray());
+    }
+
+    [Fact]
+    public void NextFrame_RebuildsIntoRetainedStorage()
+    {
+        var product = new DirectionalShadowTerrainPreparedDraws();
+        Assert.True(product.TryBegin(frameSequence: 1, estimatedCommands: 2));
+        var first = new DirectionalShadowTerrainRange(10, 3);
+        var second = new DirectionalShadowTerrainRange(20, 6);
+        product.Add(in first);
+        product.Add(in second);
+        product.Complete(frameSequence: 1);
+        long retained = product.RetainedScratchBytes;
+
+        Assert.True(product.TryBegin(frameSequence: 2, estimatedCommands: 1));
+        product.Add(in second);
+        product.Complete(frameSequence: 2);
+
+        Assert.Equal(2ul, product.BuildSequence);
+        Assert.Equal(retained, product.RetainedScratchBytes);
+        Assert.Single(product.Commands.ToArray());
+        Assert.Equal(20u, product.Commands[0].FirstIndex);
+    }
+}