NonManifoldMappingSupport.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
 
#pragma once
 
#include "Containers/Array.h"
#include "UObject/NameTypes.h"
 
namespace UE
{
namespace Geometry
{
 
// forward
class FDynamicMesh3;
class FNonManifoldSourceVertexIdAttribute;
 
 
/*
* The FNonManifoldMappingSupport is a light-weight class that exists to interpret and manage additional DynamicMesh data stored 
* when the mesh was created from a potentially non-manifold source mesh.  
*
* For context the FDynamicMesh3 is less accepting of non-manifold mesh features than some source mesh data-structures
* and conversion to a DynamicMesh may require changes to the topology ( e.g. vertex splits)  and in such cases
* this class can be use to access the mapping from DynamicMesh vertices to the source mesh vertices that generated them.
* 
* Note:
* Since this class holds pointers to named attributes owned by the DynamicMesh, unintended behavior will result if said attributes
* are removed from the mesh while an associated NomManifoldSupport object is in use. 
*
* Also, any mapping information between the DynamicMesh and source data will be corrupted by topological changes 
* to the DynamicMesh (e.g. edge splits, collapses etc).
*  
*/
class FNonManifoldMappingSupport
{
public:
 
    GEOMETRYCORE_API FNonManifoldMappingSupport(const FDynamicMesh3& Mesh);
 
 
    GEOMETRYCORE_API void Reset(const FDynamicMesh3& Mesh);
 
    /*
    * Return true if attribute data indicates that the source data that was converted to this DynamicMesh contained non-manifold vertices.
    */
    GEOMETRYCORE_API bool IsNonManifoldVertexInSource() const;
 
    /*
    * Return true if the provided DynamicMesh vertex id resulted from a non-manifold vertex in the source data.
    * @param vid - the id of a vertex in the DynamicMesh.
    * 
    * Note: the code assumes but does not check that vid is a valid vertex id
    */
    bool IsNonManifoldVertexID(const int32 vid) const
    {
        return !( vid == GetOriginalNonManifoldVertexID(vid) ); 
    }
 
    /*
    * Return the vertex ID in the potentially non-manifold data used to generate this DynamicMesh associated with the provided vertex id.   
    * In the case that the source data was actually manifold the returned vertex id will be identical to the DynamicMesh vertex id.
    * @param vid - the id of a vertex in the DynamicMesh. 
    * 
    * Note: the code assumes but does not check that vid is a valid vertex vid.
    */
    GEOMETRYCORE_API int32 GetOriginalNonManifoldVertexID(const int32 vid) const;
 
 
    // --- helper functions.
    
    /*
    * Attaches or replaces non-manifold vertex mapping data to the provided mesh.  
    * @param VertexToNonManifoldVertexIDMap - an array that maps each DynamicMesh vertex id to the associated non-manifold vertex id.
    * @return false on failure (no attribute will be attached to the DynamicMesh in this case) 
    * 
    * Note: Failure occurs if the DynamicMesh does not have attributes enabled or if the provided array is not long enough to provide a mapping value for each DynamicMesh vertex id.
    */
    static GEOMETRYCORE_API bool AttachNonManifoldVertexMappingData(const TArray<int32>& VertexToNonManifoldVertexIDMap, FDynamicMesh3& MeshInOut);
 
    /*
    *  Removes vertex mapping data related to the non-manifold nature of the source data the produced this DynamicMesh.
    * 
    *  Note: this will invalidate any NonManifoldMappingSupport object associated with this DynamicMesh, 
    *  and subsequent use of such object will produce unexpected results.
    */
    static GEOMETRYCORE_API void RemoveNonManifoldVertexMappingData(FDynamicMesh3& MeshInOut);
 
 
 
    /*
    *  Removes all  mapping data related to the non-manifold nature of the source data the produced this DynamicMesh.
    * 
    *  Note, this will invalidate any NonManifoldMappingSupport object associated with this DynamicMesh, 
    *  and subsequent use of such object will produce unexpected results.
    */
    static void RemoveAllNonManifoldMappingData(FDynamicMesh3& MeshInOut) 
    {
        RemoveNonManifoldVertexMappingData(MeshInOut);
    }
 
    /*
    * Name used to identify vertex attribute data generated during conversion to a DynamicMesh in the case that the source was non-manifold.
    */
    static GEOMETRYCORE_API FName NonManifoldMeshVIDsAttrName;
 
 
protected:
 
    const FNonManifoldSourceVertexIdAttribute*  NonManifoldSrcVIDsAttribute = nullptr;
    const FDynamicMesh3* DynamicMesh = nullptr;
};
 
 
} // namespace Geometry
} // namespace UE