Scale hidden line tolerance to model size and add optional full wireframe toggle

app.py

@@ -122,6 +122,7 @@ def _selection_path(filename):
     "front_flip": False,
     "output_format": "png",
     "label_parts": False,
+    "show_hidden_lines": False,
     "ao_mode": "ssao",
     "keep_uploads": False,
 }
@@ -301,6 +302,7 @@ def stream():
             front_flip = bool(data.get("front_flip", False))
             rotation_deg = float(data.get("rotation_deg", 0) or 0)
             label_parts = bool(data.get("label_parts", False))
+            show_hidden_lines = bool(data.get("show_hidden_lines", False))
             keep_uploads = bool(data.get("keep_uploads", False))
             # "vertex" (fast: per-vertex baked AO, can look blocky on large
             # flat panels) or "ssao" (default: screen-space AO computed
@@ -324,6 +326,7 @@ def stream():
                 "ao": ao_enabled, "ao_darkness": ao_darkness, "up_axis": up_axis,
                 "front_flip": front_flip, "rotation_deg": rotation_deg,
                 "output_format": output_format, "label_parts": label_parts,
+                "show_hidden_lines": show_hidden_lines,
                 "ao_mode": ao_mode, "keep_uploads": keep_uploads,
             })
 
@@ -396,6 +399,7 @@ def stream():
                     resolution=render_res, ao_mesh=ao_mesh,
                     ao_mode=(ao_mode if ao_enabled else None),
                     ao_max_darkness=ao_darkness / 100.0,
+                    show_hidden_lines=show_hidden_lines,
                 )
                 if part_centroids:
                     r = view_results[v]

renderer.py

@@ -300,12 +300,12 @@ def _smooth_closed_contour(coords, iterations=2):
 
 
 def render_view(mesh, view_name, center, half_span, dist, axis_cfg,
-                 resolution=1800, n_samples=30, depth_eps=0.018,
+                 resolution=1800, n_samples=30, depth_eps=None,
                  crease_angle_deg=25.0, ao_mesh=None, ao_levels=9,
                  min_contour_area=60, ao_blur_sigma_px=1.4,
                  ao_mode=None, ao_max_darkness=0.5,
                  smooth_contours=True, smooth_iterations=1,
-                 contour_supersample=4):
+                 contour_supersample=4, show_hidden_lines=False):
     """Renders one orthographic view of mesh, returning a dict with:
         outer_contours: list of Nx2 pixel-space silhouette contours
         ao_raster: (gray uint8 array, alpha bool mask) for AO shading as a
@@ -323,8 +323,24 @@ def render_view(mesh, view_name, center, half_span, dist, axis_cfg,
     ao_mode: None (no AO), "vertex" (use ao_mesh's baked vertex colors), or
     "ssao" (screen-space AO computed directly from THIS view's own depth
     buffer — no ao_mesh needed, genuinely per-view, recomputed every call).
+
+    depth_eps: tolerance (world units) used by compute_visible_edges() to
+    decide whether an edge sample is at the same depth as the nearest
+    surface there (visible) or meaningfully behind it (hidden). Defaults to
+    None, which derives it from half_span instead of using a fixed number --
+    a fixed absolute default breaks down for models exported at a very
+    different unit scale than the "normal-size car" it was tuned for (e.g.
+    a whole model just a few centimeters across): the tolerance can end up
+    larger than the model itself, so the visibility test never hides
+    anything and interior geometry bleeds through as visible lines.
+
+    show_hidden_lines: if True, skips the occlusion test entirely and keeps
+    every feature/boundary edge regardless of what's in front of it (full
+    wireframe). The silhouette is still computed normally either way.
     """
     znear, zfar = 0.01, dist * 2.2
+    if depth_eps is None:
+        depth_eps = half_span * 0.0075
     eye, up = _view_geometry(view_name, center, dist, axis_cfg)
 
     # Feature edges (dihedral angle) + true mesh boundaries. On fragmented
@@ -343,7 +359,14 @@ def render_view(mesh, view_name, center, half_span, dist, axis_cfg,
     except Exception:
         edges_v = np.empty((0, 2), dtype=int)
 
-    if len(edges_v) > 0:
+    if show_hidden_lines:
+        # Still need a depth render for the silhouette, just not for edge
+        # visibility -- every feature/boundary edge is kept as-is.
+        depth_raw, pose, cam = render_depth(mesh_welded, eye, center, up, half_span, half_span,
+                                              resolution=resolution, znear=znear, zfar=zfar)
+        depth_true = pyrender_depth_to_true_distance(depth_raw, znear, zfar)
+        segs = list(zip(mesh_welded.vertices[edges_v[:, 0]], mesh_welded.vertices[edges_v[:, 1]])) if len(edges_v) > 0 else []
+    elif len(edges_v) > 0:
         segs, depth_true, pose, cam = compute_visible_edges(
             mesh_welded, edges_v, eye, center, up, half_span, half_span,
             resolution=resolution, n_samples=n_samples, znear=znear, zfar=zfar, depth_eps=depth_eps

templates/index.html

@@ -237,6 +237,9 @@ <h2 style="margin-top:20px;">5. Detail &amp; Output</h2>
     Labels are placed at each part's center point in every view. Parts
     hidden behind other geometry still get a label there.
   </p>
+  <div class="color_row" style="margin-top:10px;">
+    <label><input type="checkbox" id="show_hidden_lines_cb"> Show hidden lines (full wireframe, ignores what's blocked from view)</label>
+  </div>
 </div>
 
 <div class="section hidden" id="generate_section">
@@ -285,6 +288,7 @@ <h2 style="margin-top:20px;">5. Detail &amp; Output</h2>
   document.getElementById('rotation_deg_input').value = prefs.rotation_deg || 0;
   document.getElementById('output_format_select').value = prefs.output_format || 'png';
   document.getElementById('label_parts_cb').checked = !!prefs.label_parts;
+  document.getElementById('show_hidden_lines_cb').checked = !!prefs.show_hidden_lines;
   document.getElementById('keep_uploads_cb').checked = !!prefs.keep_uploads;
 }
 
@@ -422,6 +426,7 @@ <h2 style="margin-top:20px;">5. Detail &amp; Output</h2>
     rotation_deg: parseFloat(document.getElementById('rotation_deg_input').value) || 0,
     output_format: document.getElementById('output_format_select').value,
     label_parts: document.getElementById('label_parts_cb').checked,
+    show_hidden_lines: document.getElementById('show_hidden_lines_cb').checked,
     keep_uploads: document.getElementById('keep_uploads_cb').checked,
   };