feat(poc): view 视觉调参画廊 4 组离屏 preview

view 加 --gallery / --preview --variant N：同一沿线中段局部段+同一相机框法，渲 4 组不同视觉参数(不透明度包络/配色/取景/背景)各存 PNG 供挑选。

新增 makeSeismicColorScale(红白蓝高对比)、makeJetColorScale(全程高饱和)、makeSolidVolumeProperty(V形实体感包络:近零背景压低但可见、中高值段普遍 0.3~0.85、半透明实心内部层次可读)、meanBrightness(画面均亮度度量)。

基线默认结构像素仅 0.07%(几乎全黑、缩角落)；4 组拉到 17~30%，亮度显著提升，fps 76~86(≫30)。推荐 var4 作默认。

tools/gpr_poc/main.cpp

@@ -680,6 +680,79 @@ geopro::core::ColorScale makeStructuralColorScale(double vmin, double vmax) {
   return cs;
 }
 
+// 地震高对比色阶（seismic 红-白-蓝）：两端饱和亮色（强正=亮红、强负=亮蓝），
+// 零附近白。比 structural 更亮、对比更狠，正负反射一眼分开。
+geopro::core::ColorScale makeSeismicColorScale(double vmin, double vmax) {
+  geopro::core::ColorScale cs;
+  const double span = (vmax > vmin) ? (vmax - vmin) : 1.0;
+  auto at = [&](double t) { return vmin + span * t; };
+  cs.addStop(at(0.00), geopro::core::Rgba{30, 60, 255, 255});    // 亮蓝(强负)
+  cs.addStop(at(0.30), geopro::core::Rgba{120, 180, 255, 255});  // 浅蓝
+  cs.addStop(at(0.50), geopro::core::Rgba{255, 255, 255, 255});  // 白(零)
+  cs.addStop(at(0.70), geopro::core::Rgba{255, 170, 120, 255});  // 浅橙
+  cs.addStop(at(1.00), geopro::core::Rgba{255, 40, 30, 255});    // 亮红(强正)
+  return cs;
+}
+
+// jet 类高饱和色阶（蓝-青-绿-黄-红）：全程高亮高饱和，最大化色彩动态范围，
+// 弱信号也能映到鲜明色相，适合「一眼铺满层次」的取向。
+geopro::core::ColorScale makeJetColorScale(double vmin, double vmax) {
+  geopro::core::ColorScale cs;
+  const double span = (vmax > vmin) ? (vmax - vmin) : 1.0;
+  auto at = [&](double t) { return vmin + span * t; };
+  cs.addStop(at(0.00), geopro::core::Rgba{0, 0, 200, 255});      // 蓝
+  cs.addStop(at(0.25), geopro::core::Rgba{0, 200, 255, 255});    // 青
+  cs.addStop(at(0.50), geopro::core::Rgba{0, 230, 60, 255});     // 绿
+  cs.addStop(at(0.75), geopro::core::Rgba{255, 230, 0, 255});    // 黄
+  cs.addStop(at(1.00), geopro::core::Rgba{255, 30, 0, 255});     // 红
+  return cs;
+}
+
+// 「实体感」不透明度包络（Task 12d gallery）：与 structural 双端斜坡不同，这里让
+// 中高值段普遍可见——背景(近零)仍压低但不归零，中高段从 floorOpacity 平滑升到
+// maxOpacity，使体读起来像半透明实心块、内部层次（而非只剩两端薄壳）可见。
+//   floorOpacity：近零背景的最低不透明度（0.05~0.12，压住但不消失）
+//   maxOpacity  ：强反射端的不透明度峰值（0.85 时近实心）
+//   midOpacity  ：中值段（半幅处）的不透明度（0.3~0.5，决定「半透明实心」观感）
+vtkSmartPointer<vtkVolumeProperty> makeSolidVolumeProperty(
+    const geopro::core::Quant& q, const geopro::core::ColorScale& cs,
+    double vminPhys, double vmaxPhys, double floorOpacity, double midOpacity,
+    double maxOpacity) {
+  constexpr int kTransferSamples = 64;
+  if (vminPhys >= vmaxPhys) vmaxPhys = vminPhys + 1.0;
+  const double qminD = static_cast<double>(q.toQ(vminPhys));
+  const double qmaxD = static_cast<double>(q.toQ(vmaxPhys));
+
+  vtkNew<vtkColorTransferFunction> color;
+  for (int t = 0; t < kTransferSamples; ++t) {
+    const double qd = qminD + (qmaxD - qminD) * t / (kTransferSamples - 1);
+    const auto qvLevel = static_cast<std::int16_t>(std::lround(qd));
+    const double phys = q.toPhys(qvLevel);
+    const auto c = cs.colorAt(phys);
+    color->AddRGBPoint(qd, c.r / 255.0, c.g / 255.0, c.b / 255.0);
+  }
+
+  // 不透明度：V 形（中段=零附近背景=floor，正负两端=max），但全程 ≥floor 且中值
+  // 段≈mid → 整体半透明实心、内部层次可见，而非两端薄壳。
+  vtkNew<vtkPiecewiseFunction> opacity;
+  opacity->AddPoint(
+      static_cast<double>(geopro::core::ScalarVolumeI16::kBlank), 0.0);
+  const double qmid = 0.5 * (qminD + qmaxD);
+  const double half = 0.5 * (qmaxD - qminD);
+  opacity->AddPoint(qminD, maxOpacity);              // 强负反射：近实心
+  opacity->AddPoint(qmid - 0.55 * half, midOpacity); // 中负段：半透明实心
+  opacity->AddPoint(qmid, floorOpacity);             // 近零背景：压低但可见
+  opacity->AddPoint(qmid + 0.55 * half, midOpacity); // 中正段：半透明实心
+  opacity->AddPoint(qmaxD, maxOpacity);              // 强正反射：近实心
+
+  auto prop = vtkSmartPointer<vtkVolumeProperty>::New();
+  prop->SetColor(color);
+  prop->SetScalarOpacity(opacity);
+  prop->SetInterpolationTypeToLinear();
+  prop->ShadeOff();
+  return prop;
+}
+
 // 参数化量化域传函：与 makeI16VolumeProperty 同逻辑，但 kMaxOpacity 可由 --opacity 控。
 // 不透明度调高时光线提前终止，fps 近乎中性甚至更快（探针认知，报告打印前后对照证实）。
 vtkSmartPointer<vtkVolumeProperty> makeTunedVolumeProperty(
@@ -1560,6 +1633,23 @@ void savePng(vtkRenderWindow* rw, const std::string& path) {
   writer->Write();
 }
 
+// 画面平均亮度（0~255）：取前缓冲 RGB 求 luma 均值。Task 12d gallery 报告用，
+// 量化「整体偏暗 vs 变亮」——背景占多数，故这是含背景的全屏均亮（横向对比有效）。
+double meanBrightness(vtkRenderWindow* rw, int w, int h) {
+  auto px = vtkSmartPointer<vtkUnsignedCharArray>::New();
+  rw->GetRGBACharPixelData(0, 0, w - 1, h - 1, /*front=*/1, px);
+  const vtkIdType np = px->GetNumberOfTuples();
+  if (np == 0) return 0.0;
+  double sum = 0.0;
+  for (vtkIdType i = 0; i < np; ++i) {
+    const double r = px->GetComponent(i, 0);
+    const double g = px->GetComponent(i, 1);
+    const double b = px->GetComponent(i, 2);
+    sum += 0.299 * r + 0.587 * g + 0.114 * b;
+  }
+  return sum / static_cast<double>(np);
+}
+
 int cmdRenderLOD(int argc, char** argv) {
   const Args a = parseArgs(argc, argv, 2);
   if (a.positional.empty()) {
@@ -2369,11 +2459,205 @@ std::size_t viewSetupDefaultFrame(ViewState* st, vtkRenderer* ren) {
   return one.size();
 }
 
+// ============================================================================
+// 视觉调参画廊（Task 12d gallery）：view --preview --variant N
+// ============================================================================
+//
+// 同一局部段(沿线中段 kViewDefaultLocalBricks 列全分辨率) + 同一相机框法
+// (ResetCamera→Elevation/Azimuth→Zoom)，只换「不透明度包络 / 配色 / 取景角度 /
+// 背景」四组视觉参数，各存一张 PNG 供控制方挑选。fps 对视觉调参近乎中性，每组实测验证。
+enum class OpacityProfile {
+  kSolid,       // V 形实体感：中高值段普遍可见，半透明实心块
+  kStructural,  // 现有双端斜坡：仅正负两端不透明（对照基线）
+};
+enum class ColorChoice { kStructural, kSeismic, kJet };
+
+struct GalleryVariant {
+  const char* name;       // 文件名后缀：view-<name>.png
+  OpacityProfile profile;
+  ColorChoice color;
+  double floorOpacity;    // 近零背景不透明度（kSolid 用）
+  double midOpacity;      // 中值段不透明度（kSolid 用）
+  double maxOpacity;      // 两端峰值不透明度
+  double exagg;           // 垂向夸张
+  double elevation;       // ResetCamera 后 Elevation
+  double azimuth;         // 再 Azimuth
+  double zoom;            // 再 Zoom 填满画面
+  double bg[3];           // 背景 RGB
+  const char* desc;       // 报告用中文说明
+};
+
+// 4 组视觉参数。值经离屏实跑挑出（详见报告）。
+const GalleryVariant kGalleryVariants[] = {
+    // var1：高不透明度实体感——seismic 亮配色 + V 形包络(中段 0.40/两端 0.85)，
+    // floor 压到 0.04：近零层间隙近透明，亮层面浮出 → 内部层状结构可读。
+    {"var1", OpacityProfile::kSolid, ColorChoice::kSeismic,
+     0.04, 0.40, 0.85, 8.0, 22.0, 28.0, 1.9, {0.05, 0.05, 0.09},
+     "高不透明度实体感：V形包络(floor0.04/mid0.40/max0.85)+seismic 亮配色，"
+     "半透明实心、内部层次可见"},
+    // var2：高对比配色——jet 全程高饱和 + 中等不透明度 V 形包络。
+    {"var2", OpacityProfile::kSolid, ColorChoice::kJet,
+     0.04, 0.32, 0.70, 8.0, 22.0, 28.0, 1.9, {0.06, 0.06, 0.10},
+     "高对比配色：jet 蓝青绿黄红全程高饱和 + 中等 V 形包络(mid0.32/max0.70)"},
+    // var3：居中正对纵截面——低 Elevation/Azimuth 摆平、正对 X-Z 长侧面(层状反射沿
+    // X 延展最清晰)、Zoom2.0 填满 ~70%；floor 压更低让层间隙透明、层面立体。
+    {"var3", OpacityProfile::kSolid, ColorChoice::kSeismic,
+     0.03, 0.38, 0.82, 9.0, 10.0, 12.0, 2.0, {0.05, 0.05, 0.09},
+     "居中正对纵截面：低 El10/Az12 摆平正对 X-Z 长侧面、Zoom2.0 填满视野，"
+     "floor0.03 凸显层面，exagg9 放大薄轴"},
+    // var4：最像真实 GPR 三维图——seismic + 略提背景亮 + 微立体角 + 实体包络。
+    {"var4", OpacityProfile::kSolid, ColorChoice::kSeismic,
+     0.035, 0.38, 0.84, 8.0, 18.0, 22.0, 2.0, {0.07, 0.08, 0.11},
+     "综合最佳：seismic + 实体包络(floor0.035/mid0.38/max0.84) + 微立体取景"
+     "(El18/Az22/Zoom2.0) + 略亮冷灰背景"},
+};
+
+geopro::core::ColorScale pickColor(ColorChoice c, double vmin, double vmax) {
+  switch (c) {
+    case ColorChoice::kSeismic: return makeSeismicColorScale(vmin, vmax);
+    case ColorChoice::kJet: return makeJetColorScale(vmin, vmax);
+    case ColorChoice::kStructural:
+    default: return makeStructuralColorScale(vmin, vmax);
+  }
+}
+
+// 渲一组画廊变体并存 PNG，报告 结构像素 / 平均亮度 / fps。返回 0=OK。
+int runGalleryVariant(const std::string& dir, const GalleryVariant& v,
+                      int frames) {
+  const int winW = 1280, winH = 800;
+  geopro::data::ChunkedVolumeStore store(dir);
+  const geopro::data::StoreMeta& m = store.meta();
+  const double vmin = m.vminPhys, vmax = m.vmaxPhys;
+  const geopro::core::ColorScale cs = pickColor(v.color, vmin, vmax);
+
+  vtkSmartPointer<vtkVolumeProperty> prop;
+  if (v.profile == OpacityProfile::kSolid) {
+    prop = makeSolidVolumeProperty(m.quant, cs, vmin, vmax, v.floorOpacity,
+                                   v.midOpacity, v.maxOpacity);
+  } else {
+    prop = makeTunedVolumeProperty(m.quant, cs, vmin, vmax, v.maxOpacity);
+  }
+
+  auto rw = makeOffscreenWindow(winW, winH);
+  vtkNew<vtkRenderer> ren;
+  ren->SetBackground(v.bg[0], v.bg[1], v.bg[2]);
+  rw->AddRenderer(ren);
+
+  vtkNew<vtkMultiBlockVolumeMapper> mapper;
+  mapper->SetRequestedRenderMode(vtkSmartVolumeMapper::GPURenderMode);
+  auto volume = vtkSmartPointer<vtkVolume>::New();
+  volume->SetMapper(mapper);
+  volume->SetProperty(prop);
+  volume->SetScale(1.0, v.exagg, v.exagg);
+  ren->AddVolume(volume);
+
+  // 局部段（沿线中段，同 viewSetupDefaultFrame 的取段法）。
+  const int totBx = store.bricksX(0);
+  const int localBx = std::min(kViewDefaultLocalBricks, totBx);
+  const int bx0 = std::max(0, totBx / 2 - localBx / 2);
+  vtkSmartPointer<vtkImageData> locImg =
+      buildLocalLevel0Image(store, m, bx0, localBx);
+  std::vector<vtkSmartPointer<vtkImageData>> one{locImg};
+  auto mb = makeMultiBlock(one);
+  mapper->SetInputDataObject(mb);
+  mapper->Update();
+
+  ren->ResetCamera();
+  vtkCamera* cam = ren->GetActiveCamera();
+  cam->Elevation(v.elevation);
+  cam->Azimuth(v.azimuth);
+  cam->Zoom(v.zoom);
+  ren->ResetCameraClippingRange();
+
+  auto capWin = vtkSmartPointer<CapturingOutputWindow>::New();
+  vtkOutputWindow::SetInstance(capWin);
+  rw->Render();
+
+  const fs::path shotDir =
+      fs::path("docs") / "superpowers" / "plans" / "poc-lod-shots";
+  fs::create_directories(shotDir);
+  const std::string pngPath =
+      (shotDir / (std::string("view-") + v.name + ".png")).string();
+  savePng(rw.Get(), pngPath);
+
+  // 结构像素：任一通道 >50（排除暗背景），度量「确有体结构」。
+  auto countStructPixels = [&]() -> vtkIdType {
+    auto px = vtkSmartPointer<vtkUnsignedCharArray>::New();
+    rw->GetRGBACharPixelData(0, 0, winW - 1, winH - 1, /*front=*/1, px);
+    vtkIdType n = 0;
+    const vtkIdType np = px->GetNumberOfTuples();
+    for (vtkIdType i = 0; i < np; ++i) {
+      if (px->GetComponent(i, 0) > 50 || px->GetComponent(i, 1) > 50 ||
+          px->GetComponent(i, 2) > 50) {
+        ++n;
+      }
+    }
+    return n;
+  };
+  const vtkIdType structPx = countStructPixels();
+  const double bright = meanBrightness(rw.Get(), winW, winH);
+
+  rw->Render();  // 预热再测 fps
+  Stopwatch sw;
+  for (int f = 0; f < frames; ++f) {
+    cam->Azimuth(360.0 / frames);
+    rw->Render();
+  }
+  const double ms = sw.elapsedMs();
+  const double fps = ms > 0 ? frames * 1000.0 / ms : 0.0;
+  const bool texErr = capWin->textureError();
+  vtkOutputWindow::SetInstance(nullptr);
+  const bool ok = !texErr && structPx > 0;
+
+  std::cout << "\n--- gallery " << v.name << " ---\n";
+  std::cout << "参数            : " << v.desc << "\n";
+  std::cout << "存图            : " << pngPath << "\n";
+  std::cout << "结构像素(>50)   : " << structPx << " / " << (winW * winH)
+            << "  (" << (100.0 * structPx / (winW * winH)) << "%)\n";
+  std::cout << "平均亮度(0-255) : " << bright << "\n";
+  std::cout << "真实 fps        : " << (ok ? std::to_string(fps) : "INVALID")
+            << "  (" << frames << " 帧旋相机)\n";
+  std::cout << "结果            : " << (ok ? "OK" : "FAIL") << "\n";
+
+  writeMetricLine(
+      "view-gallery," + std::string(v.name) + ",dir=" + dir +
+      ",profile=" + (v.profile == OpacityProfile::kSolid ? "solid" : "struct") +
+      ",floor=" + std::to_string(v.floorOpacity) +
+      ",mid=" + std::to_string(v.midOpacity) +
+      ",max=" + std::to_string(v.maxOpacity) +
+      ",exagg=" + std::to_string(v.exagg) +
+      ",el=" + std::to_string(v.elevation) +
+      ",az=" + std::to_string(v.azimuth) + ",zoom=" + std::to_string(v.zoom) +
+      ",structPx=" + std::to_string(structPx) +
+      ",bright=" + std::to_string(bright) +
+      ",fps=" + (ok ? std::to_string(fps) : "INVALID") +
+      ",png=" + pngPath);
+  return ok ? 0 : 1;
+}
+
+// view --gallery：依次渲全部 4 组变体。
+int cmdViewGallery(const std::string& dir, int frames) {
+  std::cout << "[view --gallery] storeDir=" << dir << " frames=" << frames
+            << "\n[view --gallery] 离屏闸门复检...\n";
+  if (cmdOffscreenSmoke() != 0) {
+    std::cout << "[view --gallery] 闸门失败，中止。\n";
+    return 1;
+  }
+  int rc = 0;
+  for (const auto& v : kGalleryVariants) {
+    if (runGalleryVariant(dir, v, frames) != 0) rc = 1;
+  }
+  std::cout << "\n[view --gallery] 完成，4 张图存于 "
+               "docs/superpowers/plans/poc-lod-shots/view-var{1..4}.png\n";
+  return rc;
+}
+
 int cmdView(int argc, char** argv) {
   const Args a = parseArgs(argc, argv, 2);
   if (a.positional.empty()) {
     std::cerr << "用法: gpr_poc view <storeDir> [--exagg 8] [--opacity 0.5] "
-                 "[--budget 64] [--smoke] [--preview] [--frames 90]\n";
+                 "[--budget 64] [--smoke] [--preview] [--variant N] "
+                 "[--gallery] [--frames 90]\n";
     return 2;
   }
   const std::string dir = a.positional[0];
@@ -2389,6 +2673,25 @@ int cmdView(int argc, char** argv) {
   };
   const bool smoke = hasFlag("smoke");
   const bool preview = hasFlag("preview");
+
+  // 画廊模式（Task 12d）：渲 4 组视觉调参图供挑选。优先于其余路径。
+  if (hasFlag("gallery")) {
+    return cmdViewGallery(dir, frames);
+  }
+  // 单变体：view --preview --variant N（N=1..4），只渲第 N 组。
+  if (preview && a.kv.count("variant")) {
+    const int vi = std::stoi(a.get("variant", "1"));
+    const int n = static_cast<int>(sizeof(kGalleryVariants) /
+                                   sizeof(kGalleryVariants[0]));
+    if (vi < 1 || vi > n) {
+      std::cerr << "[view] --variant 需在 1.." << n << " 之间\n";
+      return 2;
+    }
+    std::cout << "[view] storeDir=" << dir << " 单变体 variant=" << vi << "\n";
+    if (cmdOffscreenSmoke() != 0) return 1;
+    return runGalleryVariant(dir, kGalleryVariants[vi - 1], frames);
+  }
+
   std::cout << "[view] storeDir=" << dir << " exagg=" << exagg
             << " opacity=" << opacity << " budget=" << budget
             << (preview ? " [PREVIEW 离屏存图+测fps]"