Preserve chunk metadata in gaussian splat subset test

tests/Rendering/integration/gaussian_splat_scene/main.cpp

@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <cstring>
 #include <filesystem>
+#include <limits>
 #include <memory>
 #include <system_error>
 #include <vector>
@@ -137,9 +138,42 @@ GaussianSplat* CreateGaussianSplatSubset(
         }
     }
 
+    const uint32_t subsetChunkCount =
+        (subsetSplatCount + (kGaussianSplatChunkSize - 1u)) / kGaussianSplatChunkSize;
+    std::vector<GaussianSplatChunkRecord> subsetChunks(subsetChunkCount);
+    for (uint32_t chunkIndex = 0u; chunkIndex < subsetChunkCount; ++chunkIndex) {
+        const uint32_t startIndex = chunkIndex * kGaussianSplatChunkSize;
+        const uint32_t endIndex = std::min(startIndex + kGaussianSplatChunkSize, subsetSplatCount);
+
+        Vector3 minPosition(
+            std::numeric_limits<float>::max(),
+            std::numeric_limits<float>::max(),
+            std::numeric_limits<float>::max());
+        Vector3 maxPosition(
+            -std::numeric_limits<float>::max(),
+            -std::numeric_limits<float>::max(),
+            -std::numeric_limits<float>::max());
+
+        for (uint32_t subsetIndex = startIndex; subsetIndex < endIndex; ++subsetIndex) {
+            const Vector3& position = subsetPositions[subsetIndex].position;
+            minPosition.x = std::min(minPosition.x, position.x);
+            minPosition.y = std::min(minPosition.y, position.y);
+            minPosition.z = std::min(minPosition.z, position.z);
+            maxPosition.x = std::max(maxPosition.x, position.x);
+            maxPosition.y = std::max(maxPosition.y, position.y);
+            maxPosition.z = std::max(maxPosition.z, position.z);
+        }
+
+        GaussianSplatChunkRecord chunk = {};
+        chunk.posX = Vector2(minPosition.x, maxPosition.x);
+        chunk.posY = Vector2(minPosition.y, maxPosition.y);
+        chunk.posZ = Vector2(minPosition.z, maxPosition.z);
+        subsetChunks[chunkIndex] = chunk;
+    }
+
     XCEngine::Containers::Array<GaussianSplatSection> sections;
     XCEngine::Containers::Array<XCEngine::Core::uint8> payload;
-    sections.Reserve(shSection != nullptr && sh != nullptr ? 4u : 3u);
+    sections.Reserve(shSection != nullptr && sh != nullptr ? 5u : 4u);
 
     size_t payloadOffset = 0u;
     auto appendSection = [&](const GaussianSplatSection& sourceSection,
@@ -181,13 +215,21 @@ GaussianSplat* CreateGaussianSplatSubset(
             subsetSplatCount,
             sizeof(GaussianSplatSHRecord));
     }
+    GaussianSplatSection chunksSection = {};
+    chunksSection.type = GaussianSplatSectionType::Chunks;
+    chunksSection.format = GaussianSplatSectionFormat::ChunkFloat32;
+    appendSection(
+        chunksSection,
+        subsetChunks.data(),
+        subsetChunkCount,
+        sizeof(GaussianSplatChunkRecord));
 
     GaussianSplatMetadata metadata = source.GetMetadata();
     metadata.splatCount = subsetSplatCount;
     metadata.bounds = source.GetBounds();
-    metadata.chunkCount = 0u;
+    metadata.chunkCount = subsetChunkCount;
     metadata.cameraCount = 0u;
-    metadata.chunkFormat = GaussianSplatSectionFormat::Unknown;
+    metadata.chunkFormat = GaussianSplatSectionFormat::ChunkFloat32;
     metadata.cameraFormat = GaussianSplatSectionFormat::Unknown;
 
     auto* gaussianSplat = new GaussianSplat();