TMeshSimplification

Implementation of Garland & Heckbert Quadric Error Metric (QEM) Triangle Mesh Simplification

API > API/Plugins > API/Plugins/DynamicMesh

Implementation of Garland & Heckbert Quadric Error Metric (QEM) Triangle Mesh Simplification

   
Name TMeshSimplification
Type class
Header File /Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/MeshSimplification.h
Include Path #include "MeshSimplification.h"

Syntax

template<typename QuadricErrorType>  
class TMeshSimplification : public UE::Geometry::FMeshRefinerBase

Inheritance Hierarchy

Constructors

Name Remarks Include Path Unreal Specifiers
  MeshSimplification.h  
  MeshSimplification.h  

Structs

Name Remarks
FCollapseInfo Optional additional info to support edge collapses in more configurations i.e. for tri ABC, if edge AB is not constrained, but AC and BC are, it is sometimes safe to collapse AB if we also remove constraints from vertex B and edges B(AC) after the collapse.
FEdgeError  
QEdge Internal class for priority queue

Enums

Public

Name Remarks
EGeometricErrorCriteria Ways to measure geometric error
ESimplificationCollapseModes  

Protected

Name Remarks
ETargetModes  

Typedefs

Name Type Remarks Include Path
FQuadricErrorType QuadricErrorType   MeshSimplification.h
FQuadricOptions TQuadricOptionsHelper< QuadricErrorType >::FOptions   MeshSimplification.h
FSeamQuadricType TQuadricError< RealType >   MeshSimplification.h
RealType FQuadricErrorType::ScalarType   MeshSimplification.h

Variables

Public

Name Type Remarks Include Path Unreal Specifiers
bAllowSeamCollapse bool If true, we allow UV and Normal seams to collapse during simplification. MeshSimplification.h  
bLimitConstrainedSeamMovement bool If true, we prevent collapses that would move edge midpoints away from their constraint target by more than the edge constraint's threshold distance (if any) MeshSimplification.h  
bPreserveBoundaryShape bool If true, we try to keep boundary vertices on boundary. MeshSimplification.h  
bPreventTinyTriangles bool Controls whether we disallow creation of triangles with small areas inside edge operations. MeshSimplification.h  
bRetainQuadricMemory bool If false, face and vertex quadrics are recomputed in the neighborhood of each collapse, definitely slower but maybe higher quality MeshSimplification.h  
CollapseMode ESimplificationCollapseModes Controls the method used when selecting the position the results from an edge collapse. MeshSimplification.h  
CustomEdgeLengthScaleF TFunction< double(const FDynamicMesh3 &, int VertexA, int VertexB)>   MeshSimplification.h  
CustomGeometricErrorScaleF TFunction< double(const FDynamicMesh3 &, int VertexA, int VertexB)> Custom scales to apply to measured errors and edge lengths. Note this is in effect the inverse of scaling the tolerances / target lengths. MeshSimplification.h  
CustomQuadricErrorScaleF TFunction< double(const FDynamicMesh3 &, int Vertex)> Custom per-vertex quadric error scaling. Values should be greater than zero. MeshSimplification.h  
GeometricErrorConstraint EGeometricErrorCriteria Geometric error measurement/check to perform before allowing an edge collapse MeshSimplification.h  
GeometricErrorTolerance double Tolerance to use in geometric error checking MeshSimplification.h  
GroupBoundaryConstraint EEdgeRefineFlags   MeshSimplification.h  
MaterialBoundaryConstraint EEdgeRefineFlags   MeshSimplification.h  
MaxResultTriangleCount int32 If > 0, this is an absolute upper bound on the result triangle count: while the mesh has more triangles than this, the simplifier bypasses its stopping criteria (geometric error tolerance, edge-too-long rejection in SimplifyToEdgeLength, and the SimplifyToMaxError loop break) and keeps collapsing. MeshSimplification.h  
MeshBoundaryConstraint EEdgeRefineFlags When using the constraint system, these options will apply to the appropriate boundaries. MeshSimplification.h  
QuadricOptions FQuadricOptions   MeshSimplification.h  
RegularizeMethod ERegularizeSimplificationMethod Method to use to regularize, if RegularizeWeight > 0 MeshSimplification.h  
RegularizeWeight double If greater than 0, we will add a regularization term with this weight. MeshSimplification.h  

Functions

Public

Public Virtual

Name Remarks Include Path Unreal Specifiers

virtual void FastCollapsePass ( double MinEdgeLength,
int Rounds,
bool bMeshIsClosedHint,
uint32 MinTriangleCount
)

 Does N rounds of collapsing edges longer than fMinEdgeLength. MeshSimplification.h  

virtual void SimplifyToEdgeLength ( double MinEdgeLength
)

 Simplify mesh until no edges smaller than min length remain. This is not a great criteria. MeshSimplification.h  

virtual void SimplifyToMaxError ( double MaxError
)

 Simplify mesh until the quadric error of an edge collapse exceeds the specified criteria. MeshSimplification.h  

virtual void SimplifyToMinimalPlanar ( double CoplanarAngleTolDeg,
TFunctionRef< bool(int32 EdgeID)> EdgeFilterPredicate
)

 Maximally collapse mesh in a way that does not change shape at all. MeshSimplification.h  

virtual void SimplifyToTriangleCount ( int TriangleCount
)

 Simplify mesh until we reach a specific triangle count, unless geometric error criterion stops the decimation earlier. MeshSimplification.h  

virtual void SimplifyToVertexCount ( int VertexCount
)

 Simplify mesh until it has a specific vertex count MeshSimplification.h  

Protected

Name Remarks Include Path Unreal Specifiers

FQuadricErrorType AssembleEdgeQuadric ( const FDynamicMesh3::FEdge& edge
) const

 Uses pre-computed vertex, face and seam quadrics to construct the edge quadric. MeshSimplification.h  

bool CanCollapseEdge ( int edgeID,
int a,
int b,
int c,
int d,
int t0,
int t1,
int& collapse_to,
FCollapseInfo* OutCollapseInfo
) const

 Figure out if we can collapse edge eid=[a,b] under current constraint set Similar to the base class FMeshRefinerBase::CanCollapseEdge, but with simplifier-specific modifications (some more flexibility and restrictions depending on CollapseMode) MeshSimplification.h  

bool CheckIfCollapseWithinEdgeConstraintsTolerance ( int VKeep,
int VRemove,
const FVector3d& NewPosition,
int TC
)

 Check if edge collapse would violate edge constraint tolerance MeshSimplification.h  

bool CheckIfCollapseWithinGeometricTolerance ( int vid,
int vother,
const FVector3d& newv,
int tc,
int td
)

 Check if edge collapse would violate geometric error criteria MeshSimplification.h  

ESimplificationResult CollapseEdge ( int edgeID,
FVector3d vNewPos,
FDynamicMesh3::FEdgeCollapseInfo& collapseInfo,
int32 RequireKeepVert
)

 Collapse given edge. MeshSimplification.h  

FQuadricErrorType ComputeFaceQuadric ( const int tid,
FVector3d& nface,
FVector3d& c,
double& Area
) const

   MeshSimplification.h  

bool EnableInlineProjection()

 This just lets us write more concise code MeshSimplification.h  

FVector3d GetProjectedPoint ( const FVector3d& pos
)

   MeshSimplification.h  

bool IsBoundaryVertex ( int vid
) const

   MeshSimplification.h  

FQuadricErrorType MergeVertexQuadricsToEdgeQuadric ( const FDynamicMesh3::FEdge& edge
) const

   MeshSimplification.h  

FVector3d OptimalPoint ( int eid,
const FQuadricErrorType& q,
int ea,
int eb
)

 Return point that minimizes quadric error for edge [ea,eb] MeshSimplification.h  

void Precompute ( bool bMeshIsClosed
)

   MeshSimplification.h  

bool RegularizeUsesNormals()

   MeshSimplification.h  

bool RemoveIsolatedTriangle ( int tID
)

 Remove an isolated triangle. MeshSimplification.h  
Returns true while the mesh is still above MaxResultTriangleCount and we should therefore override stopping criteria (geometric error, edge-too-long, max-error loop break) to keep collapsing. MeshSimplification.h  

void UpdateVertexAttributes ( int edgeID,
int va,
int vb
)

   MeshSimplification.h  

Protected Virtual

Name Remarks Include Path Unreal Specifiers

virtual void ApplyToProjectVertices ( const TFunction< void(int)>& apply_f
)

   MeshSimplification.h  

virtual void DoSimplify()

 Top-level function that does the simplification MeshSimplification.h  

virtual void FullProjectionPass()

 Project vertices onto projection target. MeshSimplification.h  

virtual int GetNextEdge ( int CurEdgeID,
bool& bDoneOut
)

   MeshSimplification.h  

virtual FVector3d GetProjectedCollapsePosition ( int vid,
const FVector3d& vNewPos
)

 Used by collapse-edge to get projected position for new vertex MeshSimplification.h  

virtual void InitializeQueue()

   MeshSimplification.h  

virtual void InitializeSeamQuadrics()

   MeshSimplification.h  

virtual void InitializeTriQuadrics()

   MeshSimplification.h  

virtual void InitializeVertexQuadrics()

   MeshSimplification.h  

virtual void OnEdgeCollapse ( int edgeID,
int va,
int vb,
const FDynamicMesh3::FEdgeCollapseInfo& collapseInfo
)

 Subclasses can override this to implement custom behavior... MeshSimplification.h  

virtual void OnRemoveIsolatedTriangle ( int tId
)

 Subclasses can override this to implement custom behavior... MeshSimplification.h  

virtual void ProfileBeginCollapse()

   MeshSimplification.h  

virtual void ProfileBeginOps()

   MeshSimplification.h  

virtual void ProfileBeginPass()

   MeshSimplification.h  

virtual void ProfileBeginProject()

   MeshSimplification.h  

virtual void ProfileBeginSetup()

   MeshSimplification.h  

virtual void ProfileEndCollapse()

   MeshSimplification.h  

virtual void ProfileEndOps()

   MeshSimplification.h  

virtual void ProfileEndPass()

   MeshSimplification.h  

virtual void ProfileEndProject()

   MeshSimplification.h  

virtual void ProfileEndSetup()

   MeshSimplification.h  

virtual void ProjectVertex ( int vID,
IProjectionTarget* targetIn
)

   MeshSimplification.h  

virtual void Reproject()

   MeshSimplification.h  

virtual int StartEdges()

   MeshSimplification.h  

virtual void UpdateNeighborhood ( const FDynamicMesh3::FEdgeCollapseInfo& collapseInfo
)

 Update queue weight for each edge in vertex one-ring and rebuild and quadrics necessary MeshSimplification.h  

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