统一体积渲染算法与Unity版本一致

unity/Plugins/NanoVDBWrapper.cpp

@@ -0,0 +1,67 @@
+#define NANOVDB_USE_OPENVDB
+#define DLLExport __declspec(dllexport)
+
+#include <iostream>
+#include <nanovdb/util/IO.h>
+
+struct NanoVolume {
+	uint32_t* buf;
+	uint64_t byteSize;
+	uint64_t elementCount;
+	uint64_t structStride;
+} nanoVolumeStruct;
+
+extern "C" {
+	typedef void(*DebugLogCallback)(const char*);
+
+	DLLExport void SetDebugLogCallback(DebugLogCallback callback);
+	DLLExport void LoadNVDB(const char* str, struct NanoVolume** volume);
+	DLLExport void FreeNVDB(struct NanoVolume* volume);
+}
+
+DebugLogCallback UnityLog = nullptr;
+void SetDebugLogCallback(DebugLogCallback callback) {
+	UnityLog = callback;
+}
+
+nanovdb::GridHandle<nanovdb::HostBuffer> gridHandle;
+void LoadNVDB(const char* path, struct NanoVolume** volume) {
+    try {
+        // reads first grid from file
+        gridHandle = nanovdb::io::readGrid(path); 
+
+        // get a (raw) pointer to a NanoVDB grid of value type float
+        const nanovdb::FloatGrid* buf = gridHandle.grid<float>();
+
+		if (!buf) {
+			throw std::runtime_error("File did not contain a grid with value type float");
+		}
+
+		*volume = (struct NanoVolume*) malloc(sizeof(struct NanoVolume));
+
+		if (*volume == nullptr) {
+			UnityLog("Failed to allocate memory for NanoVolume struct.");
+			return;
+		}
+
+		const uint64_t byteSize = gridHandle.buffer().bufferSize();
+		const uint64_t elementCount = byteSize / sizeof(float);
+		const uint64_t structStride = sizeof(float);
+		
+		uint32_t* buffer_ptr = (uint32_t*)gridHandle.buffer().data();
+
+		(*volume)->buf = buffer_ptr;
+		(*volume)->byteSize = byteSize;
+		(*volume)->elementCount = elementCount;
+		(*volume)->structStride = structStride;
+    }
+    catch (const std::exception& e) {
+        UnityLog("An exception occurred:");
+		UnityLog(e.what());
+    }
+}
+
+void FreeNVDB(struct NanoVolume* volume) {
+	free(volume);
+	volume = nullptr;
+}