feat: make the 2.5D tracing parameters reachable from configuration

.env.example

@@ -35,8 +35,20 @@ STRUCTURA_CELLPOSE_FLOW=0.4
 # U-Nets and will NOT load here.
 STRUCTURA_CELLPOSE_MODEL=
 
-# --- 2.5D track (DEM wall tracing): gap-bridging tolerance in world units (m) ---
+# --- 2.5D track (DEM wall/edge tracing) ---
+# Gap-bridging tolerance in world units (m).
 STRUCTURA_GAP_BRIDGE_M=0.3
+# Relief smoothing scales, in PIXELS — so they depend on the DEM's resolution.
+# They decide *what* is traced: a kernel near stone size makes the response
+# follow individual stones and the line meander around them. A wall course is
+# 50-100 cm wide, so the kernels must exceed a stone. At 2.10 cm/px the default
+# (9,25,51) is only 19/53/107 cm; 101,201 is 213/423 cm.
+STRUCTURA_RELIEF_KERNELS=9,25,51
+# Threshold on the relief response: mean + k·std, over valid pixels only.
+STRUCTURA_DEM_THRESHOLD_K=1.0
+# Drop polylines shorter than this (m), and optionally simplify them (m).
+STRUCTURA_DEM_MIN_LENGTH_M=0.5
+STRUCTURA_DEM_SIMPLIFY_M=
 
 # --- Output sink: "file" (GeoPackage/GeoJSON, default), "postgis" (direct) or "api" (Django) ---
 STRUCTURA_SINK=file

src/structura/config.py

@@ -21,6 +21,14 @@ def _load_dotenv(path: Path) -> None:
         os.environ.setdefault(key.strip(), value.strip())
 
 
+def _int_tuple(name: str, default: tuple[int, ...]) -> tuple[int, ...]:
+    """Read a comma-separated integer list, e.g. STRUCTURA_RELIEF_KERNELS=51,101,201."""
+    raw = os.environ.get(name, "").strip()
+    if not raw:
+        return default
+    return tuple(int(part) for part in raw.split(",") if part.strip())
+
+
 def _opt_float(name: str) -> float | None:
     """Read an optional numeric setting. Unset *and* empty both mean "no value",
     so a commented-out or blanked line in `.env` behaves the way it looks."""
@@ -53,6 +61,12 @@ class Settings:
     cellpose_model: str | None
     # 2.5D track: gap-bridging tolerance (world units) for wall tracing
     gap_bridge_m: float
+    # 2.5D track: relief smoothing scales in *pixels*, and the tracing thresholds.
+    # The kernels decide what is traced — see WallTracer.
+    relief_kernels: tuple[int, ...]
+    dem_threshold_k: float
+    dem_min_length_m: float
+    dem_simplify_m: float | None
     # File sink (default)
     output_path: Path
     # PostGIS
@@ -88,6 +102,10 @@ def from_env(cls, dotenv: str | Path = ".env") -> "Settings":
             ),
             cellpose_model=os.environ.get("STRUCTURA_CELLPOSE_MODEL") or None,
             gap_bridge_m=float(os.environ.get("STRUCTURA_GAP_BRIDGE_M", "0.3")),
+            relief_kernels=_int_tuple("STRUCTURA_RELIEF_KERNELS", (9, 25, 51)),
+            dem_threshold_k=float(os.environ.get("STRUCTURA_DEM_THRESHOLD_K", "1.0")),
+            dem_min_length_m=float(os.environ.get("STRUCTURA_DEM_MIN_LENGTH_M", "0.5")),
+            dem_simplify_m=_opt_float("STRUCTURA_DEM_SIMPLIFY_M"),
             output_path=Path(
                 os.environ.get("STRUCTURA_OUTPUT_PATH", "./data/output/features.gpkg")
             ),

src/structura/dem/wall_tracing.py

@@ -30,10 +30,19 @@ def __init__(
         self,
         gap_bridge_m: float = 0.3,
         threshold_k: float = 1.0,
+        kernels: tuple[int, ...] = (9, 25, 51),
         min_length_m: float = 0.5,
         simplify_m: float | None = None,
     ) -> None:
         self.gap_bridge_m = gap_bridge_m
+        # Relief smoothing scales in pixels. These decide *what* is traced: a
+        # kernel near stone size makes the response follow individual stones, so
+        # the skeleton meanders around them instead of running along the course.
+        # A wall is 50-100 cm wide, so the kernels have to exceed a stone for the
+        # stones to merge into one continuous ridge. In pixels, so scale them to
+        # the DEM's resolution — at 2.10 cm/px the default (9, 25, 51) is only
+        # 19, 52 and 107 cm.
+        self.kernels = kernels
         self.threshold_k = threshold_k
         self.min_length_m = min_length_m
         self.simplify_m = simplify_m
@@ -42,7 +51,7 @@ def trace(self, dem_path: Path) -> list[Feature]:
         dem, valid, transform, crs = geo.read_dem(dem_path)
         res = abs(transform.a)  # pixel size in world units
 
-        response = relief.multiscale_relief(dem)
+        response = relief.multiscale_relief(dem, kernels=self.kernels)
         ridge = threshold_response(response, valid, self.threshold_k)
 
         return relief_response_to_features(

src/structura/pipeline.py

@@ -73,8 +73,18 @@ def run(settings: Settings, *, write: bool = True) -> list[Feature]:
         if product.kind is RasterKind.ORTHO:
             features += segmenter.segment(product.path)
         elif product.kind is RasterKind.DEM:
-            features += WallTracer(gap_bridge_m=settings.gap_bridge_m).trace(product.path)
-            features += EdgeTracer().trace(product.path)
+            features += WallTracer(
+                gap_bridge_m=settings.gap_bridge_m,
+                threshold_k=settings.dem_threshold_k,
+                kernels=settings.relief_kernels,
+                min_length_m=settings.dem_min_length_m,
+                simplify_m=settings.dem_simplify_m,
+            ).trace(product.path)
+            features += EdgeTracer(
+                threshold_k=settings.dem_threshold_k,
+                min_length_m=settings.dem_min_length_m,
+                simplify_m=settings.dem_simplify_m,
+            ).trace(product.path)
         elif product.kind is RasterKind.SEMANTIC:
             # Discovered and tagged, but not consumed yet — the class field
             # becomes a prior for the vector tracks in v0.8. Tagging it is what

tests/test_make_segmenter.py

@@ -27,6 +27,10 @@ def _settings(backend: str, **over: object) -> Settings:
         segmentation_backend=backend,
         gpu=False,
         gap_bridge_m=0.3,
+        relief_kernels=(9, 25, 51),
+        dem_threshold_k=1.0,
+        dem_min_length_m=0.5,
+        dem_simplify_m=None,
         **kwargs,  # type: ignore[arg-type]
         output_path=Path("out.gpkg"),
         pg_dsn=None,

tests/test_pipeline.py

@@ -28,6 +28,10 @@ def _settings(input_dir: Path, output_path: Path, min_area: float = 1e-4) -> Set
         cellpose_cellprob_threshold=0.0,
         cellpose_model=None,
         gap_bridge_m=0.3,
+        relief_kernels=(9, 25, 51),
+        dem_threshold_k=1.0,
+        dem_min_length_m=0.5,
+        dem_simplify_m=None,
         output_path=output_path,
         pg_dsn=None,
         pg_schema="public",