CLAUDE: Add OpenMVS 3D reconstruction section to project-details.md

Documents TERRAIN-DISP-MERGED TIFF format, INTERFRAME.corr-xml pose
convention, Elphel→COLMAP coordinate conversion, disparity-to-depth
formula, and the foliage CLI pipeline (no C++ library linking).
Co-authored-by: Claude <claude@elphel.com>

docs/project-details.md

@@ -71,6 +71,30 @@ For manual browsing, the program creates a directory with symlinks to special mo
 /media/elphel/btrfs-data/lwir16-proc/NC/models/1763232117-1763234145
 ```
 
+### FOPEN NC Summary and Map-Overlay Workflow
+The current North Carolina FOPEN linked view is:
+
+```
+/home/elphel/lwir16-proc/NC/linked/linked_1763232117-1763234145-v88/
+```
+
+Entries are timestamp-named directories using `_` instead of the decimal point in seconds. The `*-index` entries are index scenes; ordinary timestamp entries before an index entry, and after the previous index entry or start of the directory, belong to that index group. The index scene version directory contains `*-ground_planes.csv`, whose first column lists the reference-scene timestamps in the group.
+
+The spreadsheet summary output should be written under:
+
+```
+/home/elphel/lwir16-proc/NC/summaries/
+```
+
+For each ordinary timestamp directory, the useful inputs are:
+
+- `<timestamp>-elevations_histogram.csv`: first data row, first column is AGL. The cumulative elevation histogram can be converted to a forestation estimate as the relative area above a small elevation threshold, currently 1.0 m by default.
+- `<timestamp>-egomotion.csv`: after the header, each row is one 60 Hz scene. Columns 1-2 are scene index and timestamp; columns 3-8 are X/Y/Z and Euler angles relative to the reference frame. The reference-frame row has exact zeroes in all six relative pose columns. Its `lat` and `long` columns are the rectangle center for map overlays.
+
+For map overlays, the reliable first-pass orientation should come from the local `lat`/`long` motion around the reference row, not from the absolute IMS orientation or the full first-to-last segment chord. Use scene indices `ref-1` to `ref+1` when available, with adjacent egomotion rows as fallback. Assume low wind and align the image X axis opposite the local flight direction, because new objects appear at the left margin of the images. The LWIR-16 camera HFoV is 32 degrees and VFoV is `512/640 * HFoV`; combined with AGL, this defines the footprint rectangle dimensions. Labels can use the four least significant digits of timestamp seconds plus one decimal digit.
+
+Overlay generation should keep georeferenced and printable outputs separate: KML/GeoJSON for map/GIS import, and SVG/PDF for large-format vector inspection. The first NC v88 overlay bounds from all usable rectangle corners are approximately 34.8196196..34.8557247 latitude and -79.2299851..-79.1587591 longitude, about 6.5 km by 4.0 km at the mid-latitude.
+
 ## Core Processing Pipeline (Segment-Based)
 Scene sequences are processed separately in a loop such as:
 
@@ -449,6 +473,69 @@ Operational goal:
 
 This work should stay separate from factory calibration logic. The intended change is in scene/feature preparation and selection, not in the underlying multiscene `LY` optimizer.
 
+## OpenMVS 3D Reconstruction (foliage subproject)
+
+Public repo: `git@git.elphel.com:Elphel/foliage.git` (cloned at `attic/foliage/`).
+Internal context: `attic/foliage-internal/docs/FOPEN_MVS_3D_Workflow.md`.
+
+### Input files per segment reference scene
+
+| File | Content |
+|------|---------|
+| `*-TERRAIN-DISP-MERGED.tiff` | Multi-frame 32-bit float TIFF. Slices labelled `"average"` (first two) are skipped. Remaining slices are labelled with timestamps (`<ts>-<n>`) and correspond to the fused 640×512 LWIR image for each scene. |
+| `*-INTERFRAME.corr-xml` | Per-scene poses under keys `EYESIS_DCT_AUX.scenes_<ts>` = `X, Y, Z, azimuth, tilt, roll` (metres, radians) relative to the reference scene. `_dt` / `_d2t` variants are velocity/acceleration and are ignored. Reference scene timestamp in `EYESIS_DCT_AUX.timestamp_reference`. |
+
+### Coordinate conventions
+
+**Elphel camera frame** (per `GeometryCorrection`):
+- X = image-plane right, Y = image-plane up, Z < 0 along optical axis (OpenGL-style)
+- `focalLength` in mm (field in `GeometryCorrection`), `pixelSize` in μm
+- Focal length in pixels: `fl_px = focalLength_mm / (pixelSize_μm × 0.001)`
+- For 32° HFoV, 640 px width: `fl_px ≈ 1116`
+- Principal point: (319.5, 255.5) for 640×512
+
+**Rotation matrix** — mirrors `GeometryCorrection.getCommonRotMatrix()`:
+```
+R_w2c = R_roll(roll) @ R_tilt(tilt) @ R_az(azimuth)
+```
+Each factor is the transposed standard rotation (R_Y^T, R_X^T, R_Z^T respectively).
+Combined R_w2c transforms world → Elphel-camera coords.
+
+**COLMAP/OpenMVS flip** (Elphel Y-up/−Z-fwd → COLMAP Y-dn/+Z-fwd):
+```
+R_colmap = diag(1, −1, −1) @ R_w2c
+t_colmap = R_colmap @ (−C)     where C = [X, Y, Z] is the camera centre
+```
+
+Convention is validated in Phase 3 Blender smoke test (see workflow doc).
+
+### Pipeline (all CLI tools, no library linking)
+
+```
+Phase 0  scripts/elphel_to_colmap.py
+         → <out>/colmap/  (cameras.txt, images.txt, 16-bit PNGs)
+
+Phase 2  InterfaceCOLMAP → DensifyPointCloud → ReconstructMesh
+         → RefineMesh → TextureMesh
+         (one-command: scripts/run_openmvs_pipeline.sh)
+```
+
+OpenMVS is used entirely as CLI tools. No C++ library linking required.
+Set `OPENMVS_BIN=` env var if tools are not on PATH; see script header for
+build instructions.
+
+### Disparity-to-depth formula (not used by OpenMVS directly)
+
+```
+Z_m = SCENE_UNITS_SCALE × focalLength_mm × disparityRadius_mm
+      / (disparity_px × 0.001 × pixelSize_μm)
+```
+
+where `SCENE_UNITS_SCALE = 0.001` (mm → m) and `disparityRadius = 150 mm`
+(= √2 × cameraRadius, set in `GeometryCorrection`).
+The 80×64 `*_SZXY.tiff` contains pre-computed (S, Z, X, Y) per tile and
+can be used as a Phase 1 sparse seed once a suitable importer is written.
+
 ## Latest Additions
 ### Segment freezing with `keep_segments`
 Index scenes (`*-index`) contain `*-INTERFRAME.corr-xml` with keys like: