feat(render): brick 分页器（LRU 工作集，内存恒定核外渲染）

实现 geopro::render::BrickPager：驻留 ≤ budget 个解压块，
按 LRU 淘汰，与体总大小无关。requestVisible 按请求顺序更新
LRU 并淘汰至预算；get 命中返回数据指针、不改 LRU。
键为完整 BrickId(含 level)；std::list 记录 recency +
unordered_map 存数据与迭代器，touch/淘汰均 O(1)。
TDD：test_brick_pager 验证恒定驻留与最早块淘汰。

src/render/CMakeLists.txt

@@ -4,7 +4,7 @@ add_library(geopro_render STATIC
   Scene.cpp ColorLutBuilder.cpp CameraPreset.cpp VoxelFromScatters.cpp ContourBands.cpp actors/GridContourActor.cpp actors/VoxelActor.cpp actors/CurtainActor.cpp actors/MapLineActor.cpp actors/ScatterActor.cpp actors/AnomalyActor.cpp actors/ElectrodeActor.cpp actors/TerrainActor.cpp actors/AxesActor.cpp
   interact/SlicePlaneMath.cpp interact/SliceTool.cpp interact/PickInteractorStyle.cpp interact/InteractionManager.cpp interact/AnomalyDrawTool.cpp
   ground/TileMath.cpp
-  source/WholeVolumeSource.cpp)
+  source/WholeVolumeSource.cpp source/BrickPager.cpp)
 target_include_directories(geopro_render PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_link_libraries(geopro_render PUBLIC geopro_core geopro_store ${VTK_LIBRARIES} GDAL::GDAL)
 target_compile_features(geopro_render PUBLIC cxx_std_17)

src/render/source/BrickPager.cpp

@@ -0,0 +1,63 @@
+#include "render/source/BrickPager.hpp"
+
+#include "data/store/ChunkedVolumeStore.hpp"
+
+namespace geopro::render {
+
+std::size_t BrickPager::BrickIdHash::operator()(const BrickId& id) const
+    noexcept {
+  // 混合四个分量；level/块坐标均为小整数，简单移位哈希足够分散。
+  std::size_t h = static_cast<std::size_t>(id.level);
+  h = h * 31 + static_cast<std::size_t>(id.bx);
+  h = h * 31 + static_cast<std::size_t>(id.by);
+  h = h * 31 + static_cast<std::size_t>(id.bz);
+  return h;
+}
+
+BrickPager::BrickPager(const geopro::data::ChunkedVolumeStore& store,
+                       std::size_t budgetBricks)
+    : store_(store), budget_(budgetBricks) {}
+
+void BrickPager::touch(const BrickId& id) {
+  auto it = cache_.find(id);
+  if (it == cache_.end()) {
+    return;
+  }
+  // 移到 MRU 端（splice 不失效迭代器）。
+  lru_.splice(lru_.begin(), lru_, it->second.lruIt);
+  it->second.lruIt = lru_.begin();
+}
+
+void BrickPager::evictToBudget() {
+  while (cache_.size() > budget_ && !lru_.empty()) {
+    const BrickId victim = lru_.back();
+    lru_.pop_back();
+    cache_.erase(victim);
+  }
+}
+
+void BrickPager::requestVisible(const std::vector<BrickId>& visible) {
+  for (const BrickId& id : visible) {
+    auto it = cache_.find(id);
+    if (it == cache_.end()) {
+      Entry e;
+      e.data = store_.readBrick(id.level, id.bx, id.by, id.bz);
+      lru_.push_front(id);
+      e.lruIt = lru_.begin();
+      cache_.emplace(id, std::move(e));
+    } else {
+      touch(id);
+    }
+  }
+  evictToBudget();
+}
+
+const std::vector<std::int16_t>* BrickPager::get(const BrickId& id) const {
+  auto it = cache_.find(id);
+  if (it == cache_.end()) {
+    return nullptr;
+  }
+  return &it->second.data;
+}
+
+}  // namespace geopro::render

src/render/source/BrickPager.hpp

@@ -0,0 +1,66 @@
+#ifndef GEOPRO_RENDER_SOURCE_BRICKPAGER_HPP
+#define GEOPRO_RENDER_SOURCE_BRICKPAGER_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <list>
+#include <unordered_map>
+#include <vector>
+
+namespace geopro::data {
+class ChunkedVolumeStore;
+}
+
+namespace geopro::render {
+
+// 缓存键：完整 brick 标识（含 level）。
+struct BrickId {
+  int level = 0, bx = 0, by = 0, bz = 0;
+  bool operator==(const BrickId& o) const noexcept {
+    return level == o.level && bx == o.bx && by == o.by && bz == o.bz;
+  }
+};
+
+// 内存恒定的 brick LRU 缓存：任意时刻驻留 ≤ budgetBricks 个解压块，
+// 与体总大小无关。这是 C 方案核外渲染的内存控制核心。
+class BrickPager {
+ public:
+  BrickPager(const geopro::data::ChunkedVolumeStore& store,
+             std::size_t budgetBricks);
+
+  // 载入 visible 中缺失的块（经 store.readBrick 解压），按请求顺序更新 LRU；
+  // 之后淘汰最久未用的，直到 residentCount() <= budget。
+  // 若 visible.size() > budget，保留最近请求（visible 末尾）的 budget 个。
+  void requestVisible(const std::vector<BrickId>& visible);
+
+  // 命中返回该块解压数据指针（数据由 pager 持有，下次淘汰前有效）；未驻留返回
+  // nullptr。get 不改动 LRU（保持 const 语义），驻留集仅由 requestVisible 决定。
+  const std::vector<std::int16_t>* get(const BrickId& id) const;
+
+  std::size_t residentCount() const { return cache_.size(); }
+  std::size_t budget() const { return budget_; }
+
+ private:
+  struct Entry {
+    std::vector<std::int16_t> data;
+    std::list<BrickId>::iterator lruIt;  // 指向 lru_ 中本块位置
+  };
+
+  struct BrickIdHash {
+    std::size_t operator()(const BrickId& id) const noexcept;
+  };
+
+  // 把 id 移到 MRU 端（lru_ 头部）。
+  void touch(const BrickId& id);
+  // 从 LRU 端淘汰直到 residentCount() <= budget_。
+  void evictToBudget();
+
+  const geopro::data::ChunkedVolumeStore& store_;
+  std::size_t budget_;
+  std::list<BrickId> lru_;  // front = 最近使用(MRU)，back = 最久未用(LRU)
+  std::unordered_map<BrickId, Entry, BrickIdHash> cache_;
+};
+
+}  // namespace geopro::render
+
+#endif  // GEOPRO_RENDER_SOURCE_BRICKPAGER_HPP

tests/CMakeLists.txt

@@ -117,6 +117,8 @@ target_sources(geopro_tests PRIVATE render/test_tile_math.cpp)
 target_sources(geopro_tests PRIVATE render/test_slice_plane_math.cpp)
 # WholeVolumeSource(B)：读分块存储→重组整卷 VTK_SHORT image，校验 dims/类型/边缘块重组位置。
 target_sources(geopro_tests PRIVATE render/test_whole_volume_source.cpp)
+# BrickPager(C)：内存恒定的 brick LRU 分页器，驻留 ≤ budget 个解压块，证明超大体浏览内存不爆。
+target_sources(geopro_tests PRIVATE render/test_brick_pager.cpp)
 target_link_libraries(geopro_tests PRIVATE geopro_render ${VTK_LIBRARIES})
 vtk_module_autoinit(TARGETS geopro_tests MODULES ${VTK_LIBRARIES})
 

tests/render/test_brick_pager.cpp

@@ -0,0 +1,36 @@
+#include "render/source/BrickPager.hpp"
+#include "data/store/ChunkedVolumeStore.hpp"
+#include "core/algo/GprVolumeBuilder.hpp"
+#include <gtest/gtest.h>
+#include <filesystem>
+using namespace geopro;
+namespace {
+data::ChunkedVolumeStore makeStore(const std::string& dir){
+  geopro::core::BuiltI16 b; b.vol=geopro::core::ScalarVolumeI16(128,128,128);
+  for(auto& v: b.vol.data()) v=3;
+  b.quant={1.0,0.0}; b.origin={{0,0,0}}; b.spacing={{1,1,1}}; b.vminPhys=0; b.vmaxPhys=3;
+  data::ChunkedVolumeStore::write(dir, b, 64);   // 2×2×2=8 个 brick(level0)
+  return data::ChunkedVolumeStore(dir);
+}
+}
+TEST(BrickPager, BoundedMemoryLruEviction){
+  auto dir=(std::filesystem::temp_directory_path()/"gpr_pager").string();
+  std::filesystem::remove_all(dir);
+  auto store = makeStore(dir);
+  render::BrickPager pager(store, 4);
+  EXPECT_EQ(pager.budget(), 4u);
+  EXPECT_EQ(pager.residentCount(), 0u);
+  std::vector<render::BrickId> six = {
+    {0,0,0,0},{0,1,0,0},{0,0,1,0},{0,1,1,0},{0,0,0,1},{0,1,0,1} };
+  pager.requestVisible(six);
+  EXPECT_EQ(pager.residentCount(), 4u);            // 恒定 ≤ budget
+  EXPECT_EQ(pager.get(six[0]), nullptr);            // 最早请求→已淘汰
+  EXPECT_EQ(pager.get(six[1]), nullptr);
+  ASSERT_NE(pager.get(six[5]), nullptr);            // 最近请求→驻留
+  EXPECT_EQ(pager.get(six[5])->size(), 64u*64*64);
+  // 再请求一个已驻留 + 一个新的,验证 LRU 更新与恒定驻留
+  pager.requestVisible({ six[5], {0,1,1,1} });
+  EXPECT_LE(pager.residentCount(), 4u);
+  EXPECT_NE(pager.get(six[5]), nullptr);            // 刚 touch,仍在
+  std::filesystem::remove_all(dir);
+}