detectTunnelFaces constructs co-loops in given metric (#5695)

Author: Fedr

source/MRMesh/MREdgeMetric.cpp

@@ -71,6 +71,25 @@ EdgeMetric edgeCurvMetric( const Mesh & mesh, float angleSinFactor, float angleS
     return edgeCurvMetric( mesh.topology, mesh.points, angleSinFactor, angleSinForBoundary );
 }
 
+EdgeMetric edgeAbsCurvMetric( const MeshTopology& topology, const VertCoords& points, float angleSinFactor, float angleSinForBoundary )
+{
+    const float bdFactor = exp( angleSinFactor * angleSinForBoundary );
+
+    return [&topology, &points, angleSinFactor, bdFactor ]( EdgeId e ) -> float
+    {
+        auto edgeLen = edgeLength( topology, points, e );
+        if ( topology.isBdEdge( e, nullptr ) )
+            return edgeLen * bdFactor;
+
+        return edgeLen * exp( angleSinFactor * std::abs( dihedralAngleSin( topology, points, e ) ) );
+    };
+}
+
+EdgeMetric edgeAbsCurvMetric( const Mesh & mesh, float angleSinFactor, float angleSinForBoundary )
+{
+    return edgeAbsCurvMetric( mesh.topology, mesh.points, angleSinFactor, angleSinForBoundary );
+}
+
 EdgeMetric edgeTableSymMetric( const MeshTopology & topology, const EdgeMetric & metric )
 {
     MR_TIMER;

source/MRMesh/MREdgeMetric.h

@@ -30,20 +30,24 @@ namespace MR
 [[nodiscard]] MRMESH_API EdgeMetric discreteMinusAbsMeanCurvatureMetric( const Mesh & mesh );
 [[nodiscard]] MRMESH_API EdgeMetric discreteMinusAbsMeanCurvatureMetric( const MeshTopology& topology, const VertCoords& points );
 
-/// returns edge's metric that depends both on edge's length and on the angle between its left and right faces
+/// not-negative metric that depends both on edge's length and on the angle between its left and right faces
 /// \param angleSinFactor multiplier before dihedral angle sine in edge metric calculation (positive to prefer concave angles, negative - convex)
 /// \param angleSinForBoundary consider this dihedral angle sine for boundary edges;
 /// this metric is symmetric: m(e) == m(e.sym())
 [[nodiscard]] MRMESH_API EdgeMetric edgeCurvMetric( const Mesh & mesh, float angleSinFactor = 2, float angleSinForBoundary = 0 );
 [[nodiscard]] MRMESH_API EdgeMetric edgeCurvMetric( const MeshTopology& topology, const VertCoords& points, float angleSinFactor = 2, float angleSinForBoundary = 0 );
 
+/// not-negative metric that depends both on edge's length and on the angle between its left and right faces (ignoring the different between convex and concave)
+/// \param angleSinFactor multiplier before absolute value of dihedral angle sine in edge metric calculation: zero - planar case, larger values of (PI - dihedral angle)
+/// \param angleSinForBoundary consider this dihedral angle sine for boundary edges;
+/// this metric is symmetric: m(e) == m(e.sym())
+[[nodiscard]] MRMESH_API EdgeMetric edgeAbsCurvMetric( const Mesh & mesh, float angleSinFactor = 2, float angleSinForBoundary = 0 );
+[[nodiscard]] MRMESH_API EdgeMetric edgeAbsCurvMetric( const MeshTopology& topology, const VertCoords& points, float angleSinFactor = 2, float angleSinForBoundary = 0 );
+
 /// pre-computes the metric for all mesh edges to quickly return it later for any edge;
 /// input metric must be symmetric: metric(e) == metric(e.sym())
 [[nodiscard]] MRMESH_API EdgeMetric edgeTableSymMetric( const MeshTopology & topology, const EdgeMetric & metric );
 
-[[deprecated]] MR_BIND_IGNORE inline EdgeMetric edgeTableMetric( const MeshTopology & topology, const EdgeMetric & metric )
-    { return edgeTableSymMetric( topology, metric ); }
-
 /// \}
 
 } // namespace MR

source/MRMesh/MRTunnelDetector.cpp

@@ -306,6 +306,11 @@ Expected<EdgeLoop> findSmallestMetricCoLoop( const MeshTopology& topology, const
         if ( toLeft.test( e ) )
             return FLT_MAX;
         const auto m = metric0( e );
+        if ( m < 0 )
+        {
+            assert( !"metric must be not-negative" );
+            return FLT_MAX;
+        }
         if ( toLeft.test( e.sym() ) )
         {
             const auto v = topology.org( e );
@@ -405,7 +410,7 @@ Expected<FaceBitSet> detectTunnelFaces( const MeshPart & mp, const DetectTunnelS
     MR_TIMER;
     auto metric = settings.metric;
     if ( !metric )
-        metric = discreteMinusAbsMeanCurvatureMetric( mp.mesh );
+        metric = settings.buildCoLoops ? edgeLengthMetric( mp.mesh ) : discreteMinusAbsMeanCurvatureMetric( mp.mesh );
 
     FaceBitSet activeRegion = mp.mesh.topology.getFaceIds( mp.region );
     MeshPart activeMeshPart{ mp.mesh, &activeRegion };
@@ -428,7 +433,7 @@ Expected<FaceBitSet> detectTunnelFaces( const MeshPart & mp, const DetectTunnelS
         {
             ParallelFor( *basisTunnels, [&]( size_t i )
             {
-                if ( auto maybeCoLoop = findShortestCoLoop( activeMeshPart, (*basisTunnels)[i] ) )
+                if ( auto maybeCoLoop = findSmallestMetricCoLoop( mp.mesh.topology, (*basisTunnels)[i], metric, &activeRegion ) )
                     (*basisTunnels)[i] = std::move( maybeCoLoop.value() );
                 else
                 {
@@ -441,10 +446,10 @@ Expected<FaceBitSet> detectTunnelFaces( const MeshPart & mp, const DetectTunnelS
 
         const auto numBasisTunnels = basisTunnels->size();
 
-        sortPathsByLength( *basisTunnels, mp.mesh );
+        sortPathsByMetric( *basisTunnels, metric );
         for ( int i = 0; i < basisTunnels->size(); ++i )
         {
-            if ( calcPathLength( (*basisTunnels)[i], mp.mesh ) > settings.maxTunnelLength )
+            if ( calcPathMetric( (*basisTunnels)[i], metric ) > settings.maxTunnelLength )
             {
                 basisTunnels->erase( basisTunnels->begin() + i, basisTunnels->end() );
                 break;
@@ -471,7 +476,7 @@ Expected<FaceBitSet> detectTunnelFaces( const MeshPart & mp, const DetectTunnelS
 
             if ( settings.buildCoLoops && settings.filterEquivalentCoLoops && numSelectedTunnels > 0 )
             {
-                auto maybeCoLoop = findShortestCoLoop( activeMeshPart, t );
+                auto maybeCoLoop = findSmallestMetricCoLoop( mp.mesh.topology, t, metric, &activeRegion );
                 if ( !maybeCoLoop )
                     continue;
             }

source/MRMesh/MRTunnelDetector.h

@@ -42,18 +42,20 @@ MRMESH_API Expected<EdgeLoop> findShortestCoLoop( const MeshPart& mp, const Edge
 
 struct DetectTunnelSettings
 {
-    /// maximal length of tunnel loops to consider
+    /// maximal summed metric of tunnel loops to detect
     float maxTunnelLength = FLT_MAX;
 
     /// maximal number of iterations to detect all tunnels;
     /// on a big mesh with many tunnels even one iteration can take a while
     int maxIters = 1;
 
-    /// metric for detectBasisTunnels,
-    /// if no metric is given then discreteMinusAbsMeanCurvatureMetric will be used
+    /// edge metric that will be used in optimizations,
+    /// if co-loops are enabled then this metric must be not-negative,
+    /// if no metric is given then either discreteMinusAbsMeanCurvatureMetric (if buildCoLoops = false) or edgeLengthMetric (if buildCoLoops = true) will be used,
+    /// using caching via edgeTableSymMetric function can improve the performance, especially in buildCoLoops = true mode
     EdgeMetric metric;
 
-    /// if true then for every basis loop, findShortestCoLoop will be called;
+    /// if true then for every basis loop, findSmallestMetricCoLoop will be called;
     /// it typically results in shorter tunnels found, but requires more time per iteration, and more iterations to find all tunnels
     bool buildCoLoops = true;