Volumetric path tracing

.vscode/settings.json

@@ -66,7 +66,12 @@
         "typeinfo": "cpp",
         "valarray": "cpp",
         "variant": "cpp",
-        "bit": "cpp"
+        "bit": "cpp",
+        "stack": "cpp",
+        "xstring": "cpp",
+        "xutility": "cpp",
+        "xlocnum": "cpp",
+        "xtr1common": "cpp"
     },
     "python.analysis.diagnosticSeverityOverrides": {
         "reportInvalidTypeForm": "none"

parsers/vol_loader/vol2numpy.cpp

@@ -0,0 +1,116 @@
+/**
+ * @file vdb2numpy.cpp
+ * @author Qianyue He
+ * @brief Load mitsuba3 .vol volume data to numpy
+ * @version 0.1
+ * @date 2024-06-21
+ * @copyright Copyright (c) 2024
+ */
+#include <fstream>
+#include <iostream>
+#include <vector>
+#include <pybind11/stl.h>
+#include <pybind11/numpy.h>
+
+namespace py = pybind11;
+
+// Volume data intermediate representation
+struct VolumeData {
+    int xres, yres, zres;
+    int channels;
+    std::vector<float> data;
+
+    inline size_t size() const noexcept {
+        return xres * yres * zres;
+    }
+
+    inline auto shape() const noexcept {
+        return std::tuple<int, int, int, int>(xres, yres, zres, channels);
+    }
+};
+
+bool readVolumeData(const std::string& filename, VolumeData& volume) {
+    std::ifstream file(filename, std::ios::binary);
+    if (!file) {
+        std::cerr << "Error opening file: " << filename << std::endl;
+        return false;
+    }
+
+    char header[4];
+    file.read(header, 4);
+    if (header[0] != 'V' || header[1] != 'O' || header[2] != 'L' || header[3] != 3) {
+        std::cerr << "Invalid file format" << std::endl;
+        return false;
+    }
+
+    int encoding;
+    file.read(reinterpret_cast<char*>(&encoding), sizeof(int));
+    if (encoding != 1) {
+        std::cerr << "Unsupported encoding" << std::endl;
+        return false;
+    }
+
+    file.read(reinterpret_cast<char*>(&volume.xres), sizeof(int));
+    file.read(reinterpret_cast<char*>(&volume.yres), sizeof(int));
+    file.read(reinterpret_cast<char*>(&volume.zres), sizeof(int));
+
+    file.read(reinterpret_cast<char*>(&volume.channels), sizeof(int));
+    if (volume.channels != 1 && volume.channels != 3 && volume.channels != 6) {
+        std::cerr << "Unsupported number of channels" << std::endl;
+        return false;
+    }
+
+    file.seekg(24, std::ios::cur); // Skip the bounding box
+
+    int numVoxels = volume.xres * volume.yres * volume.zres * volume.channels;
+    volume.data.resize(numVoxels);
+    file.read(reinterpret_cast<char*>(volume.data.data()), numVoxels * sizeof(float));
+
+    file.close();
+    return true;
+}
+
+// mitsuba3 vol to numpy
+auto loadVol2Numpy(const std::string& filename) {
+    VolumeData volume;
+    readVolumeData(filename, volume);
+
+    py::array_t<float> vol_numpy(volume.size());
+    if (volume.channels == 1) {
+        for (int z = 0; z < volume.zres; ++z) {
+            int zy_base = z * volume.yres;
+            for (int y = 0; y < volume.yres; ++y) {
+                int zyx_base = (zy_base + y) * volume.xres;
+                for (int x = 0; x < volume.xres; ++x) {
+                    vol_numpy[zyx_base + x] = volume.data[zyx_base + x];
+                }
+            }
+        }
+    } else if (volume.channels == 3) {
+        for (int z = 0; z < volume.zres; ++z) {
+            int zy_base = z * volume.yres;
+            for (int y = 0; y < volume.yres; ++y) {
+                int zyx_base = (zy_base + y) * volume.xres;
+                for (int x = 0; x < volume.xres; ++x) {
+                    int index = (zyx_base + x) * 3;
+                    vol_numpy[index] = volume.data[index];
+                    vol_numpy[index + 1] = volume.data[index + 1];
+                    vol_numpy[index + 2] = volume.data[index + 2];
+                }
+            }
+        }
+    } else {
+        std::cerr << "Grid channel: <" << volume.channels << "> is not supported, supported channels: [1, 3]" << std::endl;
+    }
+
+    return std::tuple(vol_numpy, volume.shape());
+}
+
+PYBIND11_MODULE(vol_loader, m) {
+
+    m.doc() = "Volume grid (.vol / .vdb) loader (to numpy)\n";
+
+    m.def("vol_file_to_numpy", &loadVol2Numpy, "Load volume grid from mitsuba3 .vol file (return numpy)\n"
+        "Input: filename, input path of the file\n"
+    );
+}