Decimate and Remesh: maxBdShift parameter added

source/MRMesh/MRMeshDecimate.cpp

@@ -11,6 +11,7 @@
 #include "MRMeshDelone.h"
 #include "MRMeshSubdivide.h"
 #include "MRMeshRelax.h"
+#include "MRLineSegm.h"
 #include "MRPch/MRTBB.h"
 #include <queue>
 
@@ -410,6 +411,30 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
         std::swap( po, pd );
     }
 
+    auto smallShift = [maxBdShiftSq = sqr( settings_.maxBdShift )]( const LineSegm3f & segm, const Vector3f & p )
+    {
+        return ( closestPointOnLineSegm( p, segm ) - p ).lengthSq() <= maxBdShiftSq;
+    };
+    if ( ( !vl || !vr ) && settings_.maxBdShift < FLT_MAX )
+    {
+        if ( !smallShift( LineSegm3f{ mesh_.orgPnt( edgeToCollapse ), mesh_.destPnt( edgeToCollapse ) }, collapsePos ) )
+            return {}; // new vertex is too far from collapsing boundary edge
+        if ( !vr )
+        {
+            if ( !smallShift( LineSegm3f{ mesh_.orgPnt( mesh_.topology.prevLeftBd( edgeToCollapse ) ), collapsePos }, po ) )
+                return {}; // origin of collapsing boundary edge is too far from new boundary segment
+            if ( !smallShift( LineSegm3f{ mesh_.destPnt( mesh_.topology.nextLeftBd( edgeToCollapse ) ), collapsePos }, pd ) )
+                return {}; // destination of collapsing boundary edge is too far from new boundary segment
+        }
+        if ( !vl )
+        {
+            if ( !smallShift( LineSegm3f{ mesh_.orgPnt( mesh_.topology.prevLeftBd( edgeToCollapse.sym() ) ), collapsePos }, pd ) )
+                return {}; // destination of collapsing boundary edge is too far from new boundary segment
+            if ( !smallShift( LineSegm3f{ mesh_.destPnt( mesh_.topology.nextLeftBd( edgeToCollapse.sym() ) ), collapsePos }, po ) )
+                return {}; // origin of collapsing boundary edge is too far from new boundary segment
+        }
+    }
+
     float maxOldAspectRatio = settings_.maxTriangleAspectRatio;
     float maxNewAspectRatio = 0;
     const float edgeLenSq = ( po - pd ).lengthSq();
@@ -420,7 +445,7 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
     originNeis_.clear();
     triDblAreas_.clear();
     Vector3d sumDblArea_;
-    bool oBd = false; // there is a boundary edge incident to org( edgeToCollapse )
+    EdgeId oBdEdge; // a boundary edge !right(e) incident to org( edgeToCollapse )
     for ( EdgeId e : orgRing0( topology, edgeToCollapse ) )
     {
         const auto eDest = topology.dest( e );
@@ -434,7 +459,8 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
         maxNewEdgeLenSq = std::max( maxNewEdgeLenSq, ( collapsePos - pDest ).lengthSq() );
         if ( !topology.left( e ) )
         {
-            oBd = true;
+            oBdEdge = topology.next( e );
+            assert( topology.isLeftBdEdge( oBdEdge ) );
             continue;
         }
 
@@ -451,9 +477,13 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
         }
         maxOldAspectRatio = std::max( maxOldAspectRatio, triangleAspectRatio( po, pDest, pDest2 ) );
     }
+    if ( oBdEdge
+        && !smallShift( LineSegm3f{ po, mesh_.destPnt( oBdEdge ) }, collapsePos )
+        && !smallShift( LineSegm3f{ po, mesh_.orgPnt( topology.prevLeftBd( oBdEdge ) ) }, collapsePos ) )
+            return {}; // new vertex is too far from both existed boundary edges
     std::sort( originNeis_.begin(), originNeis_.end() );
 
-    bool dBd = false; // there is a boundary edge incident to dest( edgeToCollapse )
+    EdgeId dBdEdge; // a boundary edge !right(e) incident to dest( edgeToCollapse )
     for ( EdgeId e : orgRing0( topology, edgeToCollapse.sym() ) )
     {
         const auto eDest = topology.dest( e );
@@ -466,7 +496,8 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
         maxNewEdgeLenSq = std::max( maxNewEdgeLenSq, ( collapsePos - pDest ).lengthSq() );
         if ( !topology.left( e ) )
         {
-            dBd = true;
+            dBdEdge = topology.next( e );
+            assert( topology.isLeftBdEdge( dBdEdge ) );
             continue;
         }
 
@@ -483,8 +514,12 @@ VertId MeshDecimator::collapse_( EdgeId edgeToCollapse, const Vector3f & collaps
         }
         maxOldAspectRatio = std::max( maxOldAspectRatio, triangleAspectRatio( pd, pDest, pDest2 ) );
     }
+    if ( dBdEdge
+        && !smallShift( LineSegm3f{ pd, mesh_.destPnt( dBdEdge ) }, collapsePos )
+        && !smallShift( LineSegm3f{ pd, mesh_.orgPnt( topology.prevLeftBd( dBdEdge ) ) }, collapsePos ) )
+            return {}; // new vertex is too far from both existed boundary edges
 
-    if ( vl && vr && oBd && dBd )
+    if ( vl && vr && oBdEdge && dBdEdge )
         return {}; // prohibit collapse of an inner edge if it brings two boundaries in touch
 
     if ( !tinyEdge && maxNewAspectRatio > maxOldAspectRatio && maxOldAspectRatio <= settings_.criticalTriAspectRatio )
@@ -834,6 +869,7 @@ bool remesh( MR::Mesh& mesh, const RemeshSettings & settings )
     DecimateSettings decs;
     decs.strategy = DecimateStrategy::ShortestEdgeFirst;
     decs.maxError = settings.targetEdgeLen * uni;
+    decs.maxBdShift = settings.maxBdShift;
     decs.region = settings.region;
     decs.packMesh = settings.packMesh;
     decs.progressCallback = subprogress( settings.progressCallback, 0.5f, 0.95f );

source/MRMesh/MRMeshDecimate.h

@@ -38,6 +38,8 @@ struct DecimateSettings
     float maxError = 0.001f;
     /// Maximal possible edge length created during decimation
     float maxEdgeLen = FLT_MAX;
+    /// Maximal shift of a boundary during one edge collapse
+    float maxBdShift = FLT_MAX;
     /// Maximal possible aspect ratio of a triangle introduced during decimation
     float maxTriangleAspectRatio = 20;
     /// the algorithm will ignore dihedral angle check if one of triangles had aspect ratio equal or more than this value;
@@ -190,6 +192,8 @@ struct RemeshSettings
     float edgeLenUniformity = 0.5f;
     /// Improves local mesh triangulation by doing edge flips if it does change dihedral angle more than on this value
     float maxAngleChangeAfterFlip = 30 * PI_F / 180.0f;
+    /// Maximal shift of a boundary during one edge collapse
+    float maxBdShift = FLT_MAX;
     /// This option in subdivision works best for natural surfaces, where all triangles are close to equilateral and have similar area,
     /// and no sharp edges in between
     bool useCurvature = false;

source/MRMesh/MRMeshDecimateParallel.cpp

@@ -18,6 +18,7 @@ DecimateResult decimateParallelMesh( MR::Mesh & mesh, const DecimateParallelSett
     seqSettings.strategy = settings.strategy;
     seqSettings.maxError = settings.maxError;
     seqSettings.maxEdgeLen = settings.maxEdgeLen;
+    seqSettings.maxBdShift = settings.maxBdShift;
     seqSettings.maxTriangleAspectRatio = settings.maxTriangleAspectRatio;
     seqSettings.criticalTriAspectRatio = settings.criticalTriAspectRatio;
     seqSettings.stabilizer = settings.stabilizer;

source/MRMesh/MRMeshDecimateParallel.h

@@ -21,7 +21,9 @@ struct DecimateParallelSettings
     ///   stop the decimation as soon as the shortest edge in the mesh is greater than this value
     float maxError = 0.001f;
     /// Maximal possible edge length created during decimation
-    float maxEdgeLen = 1;
+    float maxEdgeLen = FLT_MAX;
+    /// Maximal shift of a boundary during one edge collapse
+    float maxBdShift = FLT_MAX;
     /// Maximal possible aspect ratio of a triangle introduced during decimation
     float maxTriangleAspectRatio = 20;
     /// the algorithm will try to eliminate triangles with equal or larger aspect ratio, ignoring normal orientation checks

source/MRMesh/MRPolylineDecimate.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "MRMeshFwd.h"
+#include <cfloat>
 #include <climits>
 #include <functional>
 
@@ -20,7 +21,7 @@ struct DecimatePolylineSettings
     /// Limit from above on the maximum distance from moved vertices to original contour
     float maxError = 0.001f;
     /// Maximal possible edge length created during decimation
-    float maxEdgeLen = 1;
+    float maxEdgeLen = FLT_MAX;
     /// Stabilizer is dimensionless coefficient.
     /// The larger is stabilizer, the more Decimator will strive to retain the density of input points.
     /// If stabilizer is zero, then only the shape of input line will be preserved.