fix unwrap failures on collapsed preseed uvs

Author: danielboxer

dev/tests/test_seams.py

@@ -57,6 +57,7 @@
     uv_fit,
     uv_island_groups,
     uv_topology,
+    uvs_collapsed,
     vertex_components,
 )
 from seams.islands import absorb_fragments, split_pieces  # noqa: E402
@@ -1820,3 +1821,13 @@ def test_flatten_distortion_reads_a_mirrored_island_like_its_source():
     mirrored = [[(0.0, 0.0), (-1.0, 0.0), (-1.0, 1.0), (0.0, 1.0)]]
     value = flatten_distortion(FLAT_QUAD_VERTS, [(0, 1, 2, 3)], mirrored, [0])
     assert abs(value - 4.0) < 1e-9
+
+
+def test_collapsed_uvs_are_detected():
+    point = (0.1, 0.9987)
+    assert uvs_collapsed([[point, point, point]] * 100)
+
+
+def test_real_uvs_are_not_collapsed():
+    quad = [(0.0, 0.0), (0.01, 0.0), (0.01, 0.01), (0.0, 0.01)]
+    assert not uvs_collapsed([quad])

engine/optcuts/VERSION

@@ -1 +1 @@
-1.16.0
+1.16.1

engine/optcuts/src/Scaffold.cpp

@@ -179,6 +179,10 @@ Scaffold::Scaffold(const TriMesh &mesh, Eigen::MatrixXd UV_bnds,
     // "q" for high quality mesh generation
     // "Q" for quiet mode (no output)
 
+    // degenerate boundaries can leave no triangles, crashing computeFeatures
+    if (airMesh.F.rows() == 0)
+        throw std::runtime_error("air mesh triangulation came back empty");
+
     airMesh.V_rest.resize(airMesh.V.rows(), 3);
     airMesh.V_rest << airMesh.V, Eigen::VectorXd::Zero(airMesh.V.rows());
     airMesh.areaThres_AM =

engine/optcuts/src/uvgami.cpp

@@ -1209,10 +1209,23 @@ int main(int argc, char *argv[]) {
         for (int c = 0; c < n_components; ++c) {
             inverted[c] = !temp.checkInversion(true, chartTris[c]);
         }
-        bool anyInversion = false, allDisks = true;
+
+        // zero area passes the inversion test and a point boundary evades
+        // the crossing test, but a collapsed chart cannot seed the solve
+        std::vector<bool> degenerate(n_components, false);
+        for (int triI = 0; triI < temp.F.rows(); ++triI) {
+            const Eigen::RowVector3i &tri = temp.F.row(triI);
+            const Eigen::RowVector2d e1 = temp.V.row(tri[1]) - temp.V.row(tri[0]);
+            const Eigen::RowVector2d e2 = temp.V.row(tri[2]) - temp.V.row(tri[0]);
+            if (e1[0] * e2[1] - e1[1] * e2[0] <= 0.0)
+                degenerate[C[triI]] = true;
+        }
+
+        bool anyInversion = false, allDisks = true, anyDegenerate = false;
         for (int c = 0; c < n_components; ++c) {
             anyInversion = anyInversion || inverted[c];
             allDisks = allDisks && isDisk[c];
+            anyDegenerate = anyDegenerate || degenerate[c];
         }
         // a stitch run can keep charts with holes: an interior split the
         // engine never merged back leaves a slit, and the machinery is
@@ -1249,19 +1262,22 @@ int main(int argc, char *argv[]) {
         // whole-map decision first, so a map that was kept before is still
         // kept byte for byte
         keepInputUV = (allDisks || stitchKeepable) && !anyInversion &&
-                      crossingVerts.empty();
+                      !anyDegenerate && crossingVerts.empty();
 
-        int badInverted = 0, badOverlapping = 0, badNonDisk = 0;
+        int badInverted = 0, badOverlapping = 0, badNonDisk = 0,
+            badDegenerate = 0;
         if (keepInputUV) {
             keepChart.assign(n_components, true);
             keptCharts = n_components;
         } else {
             for (int c = 0; c < n_components; ++c) {
-                keepChart[c] =
-                    isDisk[c] && !overlaps[c] && !inverted[c] && !pinched[c];
+                keepChart[c] = isDisk[c] && !overlaps[c] && !inverted[c] &&
+                               !pinched[c] && !degenerate[c];
                 keptCharts += keepChart[c];
                 if (inverted[c]) {
                     ++badInverted;
+                } else if (degenerate[c]) {
+                    ++badDegenerate;
                 } else if (overlaps[c]) {
                     ++badOverlapping;
                 } else if (!isDisk[c]) {
@@ -1280,8 +1296,8 @@ int main(int argc, char *argv[]) {
         } else if (!keepInputUV) {
             std::cout << "kept " << keptCharts << " of " << n_components
                       << " input UV charts, re-cutting " << badInverted
-                      << " inverted, " << badOverlapping
-                      << " self-intersecting, " << badNonDisk
+                      << " inverted, " << badDegenerate << " degenerate, "
+                      << badOverlapping << " self-intersecting, " << badNonDisk
                       << " not disk-topology" << std::endl;
         }
     }

src/engines/optcuts/__init__.py

@@ -9,9 +9,9 @@
     seam_flags,
     seam_restrictions,
 )
-from ...seams import FlattenError
+from ...seams import FlattenError, uvs_collapsed
 from ...utils.io import print_stdin
-from ...utils.mesh import deselect_all, validate_obj
+from ...utils.mesh import corner_uvs, deselect_all, validate_obj
 from ...utils.ui import only_active
 from ..binary_engine import BinaryEngine
 from .install import OPTCUTS, UVGAMI_OT_install_optcuts
@@ -251,9 +251,12 @@ def piece_uses_uvs(self, obj, props, has_uvs):
         # auto mode routes per loose part: a piece the preseed skipped has no
         # seams and goes to the engine bare, to be cut from scratch. With
         # import uvs on, organic pieces keep the user's map instead
-        if not props.optcuts.is_auto or props.import_uvs:
+        if props.optcuts.is_auto and not props.import_uvs:
+            has_uvs = has_uvs and bool(seam_flags(obj.data).any())
+        if not has_uvs or obj.data.uv_layers.active is None:
             return has_uvs
-        return has_uvs and bool(seam_flags(obj.data).any())
+        # a collapsed flatten goes bare too, the engine can fail re-cutting it
+        return not uvs_collapsed(corner_uvs(obj.data))
 
     def build_args(self, ctx, input_path, props):
         bounds = {"LESS_STRETCH": "4.05", "BALANCED": "4.2", "FEWER_SEAMS": "5.0"}

src/engines/optcuts/install.py

@@ -3,7 +3,7 @@
 from ..binary_engine import EngineRelease, InstallEngineTask
 
 # must match engine/optcuts/VERSION (check-engine-versions.yml fails on drift)
-OPTCUTS_VERSION = "1.16.0"
+OPTCUTS_VERSION = "1.16.1"
 OPTCUTS = EngineRelease("optcuts", "Optcuts", OPTCUTS_VERSION, "2 MB")
 
 

src/manager.py

@@ -72,6 +72,7 @@ def _reset_session(self):
         self.pending_transfers = []
         self.transfer_uv_failed = False
         self.transfer_uv_fail_detail = ""
+        self.transfer_uv_missing_pieces = False
         self.transfer_uv_split_count = 0
         self.error_code = 0
         self.error_stderr = ""
@@ -486,6 +487,16 @@ def _import_and_finalize(self, unwrap, path, edge_path, added_edges):
                     if obj == output:
                         pack_index = i
                         break
+            # a group missing pieces can never cover every input face
+            group = unwrap.join_job
+            if group is not None and len(group.finished) < group.expected:
+                failed = group.expected - len(group.finished)
+                self.transfer_uv_missing_pieces = True
+                report = TransferReport(
+                    False, 0, f"{failed} of {group.expected} parts failed to unwrap"
+                )
+                self._settle_transfer(job, output, pack_index, report)
+                return
             if isinstance(job, ProxyUVs):
                 report = job.start(self.input[job], output)
                 if report is None:
@@ -722,10 +733,10 @@ def _finish_batch(self):
 
             if self.transfer_uv_failed:
                 detail = self.transfer_uv_fail_detail or "unknown reason"
-                msg.append(
-                    f"UV transfer failed: {detail}."
-                    " This can happen with cuts or symmetry enabled."
-                )
+                line = f"UV transfer failed: {detail}."
+                if not self.transfer_uv_missing_pieces:
+                    line += " This can happen with cuts or symmetry enabled."
+                msg.append(line)
 
             if self.transfer_uv_split_count > 0:
                 count = self.transfer_uv_split_count

src/seams/__init__.py

@@ -39,6 +39,7 @@
     uv_area_fit,
     uv_fit,
     uv_island_groups,
+    uvs_collapsed,
     vertex_components,
 )
 from .pipeline import is_hard_surface, seam_edges
@@ -126,5 +127,6 @@
     "uv_fit",
     "uv_island_groups",
     "uv_topology",
+    "uvs_collapsed",
     "vertex_components",
 ]

src/seams/mesh.py

@@ -102,6 +102,15 @@ def signed_area(pts):
     return total / 2
 
 
+# between a collapsed map's float noise and any real packed map's area
+COLLAPSED_UV_AREA = 1e-8
+
+
+def uvs_collapsed(polygons):
+    """Whether a uv map is crushed to points, a failed flatten's signature."""
+    return sum(abs(signed_area(pts)) for pts in polygons) < COLLAPSED_UV_AREA
+
+
 def island_groups(faces, seams, edges):
     """Faces grouped into uv islands: joined by interior edges not on a seam."""
     parent = list(range(len(faces)))