chore: import upstream snapshot with attribution

2026-07-13 13:18:05 +08:00
commit acd8e21031
297 changed files with 56514 additions and 0 deletions
@@ -0,0 +1,60 @@
+#pragma once
+#include <array>
+#include <eigen3/Eigen/Dense>
+#include <memory>
+#include <vector>
+
+namespace splat {
+class SH {
+public:
+    SH() noexcept;
+    SH(size_t size);
+    SH(const SH& other);
+    SH(SH&& other) noexcept;
+
+    SH& operator=(const SH& other);
+    SH& operator=(SH&& other) noexcept;
+
+    void swap(SH& other) noexcept;
+
+    SH& set_zero() noexcept;
+    SH& add_multiplied(const SH& other, float scalar) noexcept;
+
+    const float& operator[](size_t index) const;
+    float& operator[](size_t index);
+
+    float* data() noexcept;
+    size_t size() const noexcept;
+
+    ~SH() noexcept;
+
+private:
+    void reset() noexcept;
+
+    size_t size_;
+    std::unique_ptr<float[]> ptr;
+};
+
+struct Gaussian {
+    Eigen::Vector3f mean;
+    Eigen::Vector3f scale;
+    Eigen::Vector4f rotation;
+    Eigen::Matrix3f covariance;
+    SH sh;
+    float opacity;
+    Eigen::AlignedBox3f bounding_box;
+
+    void compute_covariance();
+    void decompose_covariance();
+    void compute_bounding_box(float k = 3.0f);
+    float area() const;
+};
+
+struct Splat {
+    std::vector<Gaussian> gaussians;
+    Eigen::AlignedBox3f bounding_box;
+
+    void compute_bounding_box();
+    void compute_compact_bounding_box();
+};
+} // namespace splat
@@ -0,0 +1,17 @@
+#pragma once
+#include <splat/splat.h>
+#include <type_traits>
+#include <vector>
+
+namespace splat::block {
+namespace detail {
+std::vector<Splat> split(const Splat& splat, size_t max_block_size);
+} // namespace detail
+
+template<typename T>
+    requires std::is_same_v<std::remove_reference_t<T>, Splat>
+std::vector<Splat> split(T&& input, double precision) {
+    auto max_block_size = static_cast<size_t>(static_cast<double>(input.gaussians.size()) * precision);
+    return detail::split(input, max_block_size);
+}
+} // namespace splat::block
@@ -0,0 +1,43 @@
+#pragma once
+#include <container_helpers.h>
+#include <cstdint>
+#include <splat/splat.h>
+#include <vector>
+
+namespace splat::lod {
+namespace detail {
+Splat reduce_gaussians(size_t id, const Splat& splat, size_t target_count, float scale_boost, size_t max_step);
+}
+
+struct SplatLod {
+    std::vector<Splat> splats;
+    std::vector<uint32_t> levels;
+};
+
+struct SplatLevelParameters {
+    float precision;
+    float scale_boost;
+};
+
+template<typename T>
+    requires requires(T) {
+        requires helpers::container::range_of<T, SplatLevelParameters>;
+    }
+inline void generate_lod(size_t id, SplatLod& lod, T&& parameters, size_t min_size, size_t max_step) {
+    auto base_count = lod.splats.back().gaussians.size();
+    for (auto& parameter : parameters) {
+        auto target_count = std::max<size_t>(static_cast<size_t>(std::floor(static_cast<double>(base_count) * parameter.precision)), 1);
+        auto& current = lod.splats.back();
+        if (current.gaussians.size() > min_size && target_count < current.gaussians.size()) {
+            auto generated = detail::reduce_gaussians(
+                id,
+                current,
+                target_count,
+                parameter.scale_boost,
+                max_step);
+            lod.splats.push_back(std::move(generated));
+        }
+        lod.levels.push_back(lod.splats.size() - 1);
+    }
+}
+} // namespace splat::lod