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  3. FRemesher

FRemesher

[FRemesher](API\Plugins\DynamicMesh\FRemesher) implements edge flip/split/collapse/smooth Remeshing.

API > API/Plugins > API/Plugins/DynamicMesh

Inheritance Hierarchy

References

   
Module DynamicMesh
Header /Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/Remesher.h
Include #include "Remesher.h"

Syntax

class FRemesher : public UE::Geometry::FMeshRefinerBase

Remarks

FRemesher implements edge flip/split/collapse/smooth Remeshing. The basic process is very similar to the one described in: A Remeshing Approach to Multiresolution Modeling. Botsch & Kobbelt, SGP 2004. https://graphics.uni-bielefeld.de/publications/sgp04.pdf

In the iterative usage, each call to BasicRemeshPass() makes a pass over the mesh and attempts to update the topology and shape to satisfy the target criteria. This function iterates over the mesh edges and calls ProcessEdge(), which tries to Collapse, then Split, then Flip the edge. After the topology pass, we optionally do a full-mesh Smoothing pass, and a full-mesh Reprojection pass, to project onto a target surface.

A highly flexible constraint system can be used to control what is allowed to happen to individual edges and vertices, as well as Project vertices onto arbitrary proejction targets. This is done via FMeshConstraints which is set in the MeshRefinerBase base class.

Many aspects of the algorithm can be controlled by the public variables in the block below. In addition many of the core internal functions can be overriden to customize behavior. Various callbacks functions are called when topology changes occur which allows you to for instance track changed regions of the mesh.

Variables

  Type Name Description
Public variable bool bEnableCollapses Controls whether edge collapses are allowed during remeshing pass
Public variable bool bEnableFlips Configuration variables and flagsControls whether edge-flips are allowed during remeshing pass
Public variable bool bEnableParallelProjection Enable parallel projection. Only applied in AfterRefinement mode
Public variable bool bEnableParallelSmooth Enable parallel smoothing.
Public variable bool bEnableSmoothing Controls whether vertex smoothing is applied during remeshing pass
Public variable bool bEnableSmoothInPlace If smoothing is done in-place, we don't need an extra buffer, but also there will some randomness introduced in results.
Public variable bool bEnableSplits Controls whether edge splits are allowed during remeshing pass
Protected variable bool bMeshIsClosed We can avoid some checks/etc if we know that the mesh has no boundary edges.
Public variable bool bPreventNormalFlips Controls whether we try to prevent normal flips inside operations and smoothing.
Public variable bool bPreventTinyTriangles Controls whether we disallow creation of triangles with small areas inside edge operations.
Protected variable int COUNT_COLLAPSES  
Protected variable int COUNT_FLIPS  
Protected variable int COUNT_SPLITS Testing/debug/profiling stuff profiling functions, turn on ENABLE_PROFILING to see output in console
Public variable TFunction< FVector3d(const FDynamicMesh3 &, int, double)> CustomSmoothF Override default smoothing function
Public variable TFunction< double(const FDynamicMesh3 &, int)> CustomSmoothSpeedF Override constant SmoothSpeedT with function
Public variable EFlipMetric FlipMetric Type of flip metric that will be applied
Protected variable int MaxEdgeID  
Public variable double MaxEdgeLength Maximum target edge length. Edges longer than this will be split if possible.
Public variable double MinEdgeLength Minimum target edge length. Edges shorter than this will be collapsed if possible.
Public variable double MinLengthFlipThresh For MinEdgeLength metric, only flip if NewLength < (MinLengthFlipThresh * CurLength)
Public variable int ModifiedEdgesLastPass Number of edges that were modified in previous Remesh pass.
Protected variable const int ModuloPrime StartEdges() and GetNextEdge() control the iteration over edges that will be refined.
Public variable double SmoothSpeedT Smoothing speed, in range [0,1]
Public variable ESmoothTypes SmoothType Type of smoothing that will be applied unless overridden by CustomSmoothF
Protected variable TArray< bool > TempFlagBuffer  
Protected variable TDynamicVector< FVector3d > TempPosBuffer  

Constructors

  Type Name Description
Protected function    
Public function  

FRemesher ( FDynamicMesh3* MeshIn
)

 Public API

Destructors

  Type Name Description
Public function Virtual    

Functions

  Type Name Description
Protected function Virtual void

ApplyToProjectVertices ( const TFunction< void(int)>& VertexProjectFunc
)

 Apply the given projection function to all vertices in the mesh.
Protected function Virtual void

ApplyToSmoothVertices ( const TFunction< void(int)>& VertexSmoothFunc
)

 FullSmoothPass_Buffer this to calls VertexSmoothFunc for each vertex of the mesh.
Protected function Virtual void

ApplyVertexBuffer ( bool bParallel
)

  
Public function Virtual void Linear edge-refinement pass, followed by smoothing and projection
Protected function Virtual FVector3d

ComputeSmoothedVertexPos ( int VertexID,
TFunction< FVector3d(const FDynamicMesh3&, int, double)> SmoothFunc,
bool& bModified
)

 Computes smoothed vertex position w/ proper constraints/etc. Does not modify mesh.
Protected function Const bool This just lets us write more concise code
Protected function Virtual void

FullProjectionPass ( bool bParallel
)

 Project vertices onto projection target.
Protected function Virtual void

FullSmoothPass_Buffer ( bool bParallel
)

 Applies a smoothing pass to the mesh, storing intermediate positions in a buffer and then writing them at the end (so, no order effect)
Protected function Virtual int

GetNextEdge ( int CurEdgeID,
bool& bDone
)

  
Protected function Virtual FVector3d

GetProjectedCollapsePosition ( int VertexID,
const FVector3d& vNewPos
)

 Used by collapse-edge to get projected position for new vertex
Protected function Virtual TFunction< FVector3d(const FDynamicMesh3 &, int, double)> Returns the function we want to use to compute a smoothed vertex position - will be CustomSmoothF if set, otherwise one of cotan/meanvalue/uniform
Protected function Virtual void  
Protected function void

MoveVerticesParallel ( TFunction< FVector3d(int, bool&)> NewVertexPosition
)

 Move all vertices in parallel.
Public function Virtual void

OnEdgeCollapse ( int EdgeID,
int VertexA,
int VertexB,
const FDynamicMesh3::FEdgeCollapseInfo& CollapseInfo
)

 Callback for subclasses to override to implement custom behavior
Public function Virtual void

OnEdgeFlip ( int EdgeID,
const FDynamicMesh3::FEdgeFlipInfo& FlipInfo
)

 Callback for subclasses to override to implement custom behavior
Public function Virtual void

OnEdgeSplit ( int EdgeID,
int VertexA,
int VertexB,
const FDynamicMesh3::FEdgeSplitInfo& SplitInfo
)

 Callbacks and in-progress informationCallback for subclasses to override to implement custom behavior
Public function Virtual void We can speed things up if we precompute some invariants.
Protected function Virtual EProcessResult

ProcessEdge ( int edgeID
)

  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void  
Protected function Virtual void

ProjectVertex ( int VertexID,
IProjectionTarget* UseTarget
)

 Project a single vertex using the given target.
Public function void

SetTargetEdgeLength ( double fLength
)

 Set min/max edge-lengths to sane values for given target edge length
Protected function Virtual int  
Protected function Virtual void

UpdateAfterSplit ( int edgeID,
int va,
int vb,
const FDynamicMesh3::FEdgeSplitInfo& splitInfo
)

 After we split an edge, we have created a new edge and a new vertex.

Enums

  Type Name Description
Public enum EFlipMetric Available Edge Flip metrics  
Protected enum EProcessResult    
Public enum ESmoothTypes Built-in Smoothing types  

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