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2025-05-18 13:04:45 +08:00

88 lines
2.4 KiB
C++

// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
#include "MathUtil.h"
#include "VectorTypes.h"
#include "GeometryTypes.h"
#include "Polygon2.h"
#include "DynamicMesh/DynamicMesh3.h"
#define UE_API DYNAMICMESH_API
namespace UE
{
namespace Geometry
{
/**
* Calculate a Convex Hull for a Mesh by first Projecting all vertices to a plane, computing a
* 2D convex polygon that contains them, and then sweeping that 2D hull to create an extruded 3D volume.
*/
class FMeshProjectionHull
{
public:
/** Input Mesh */
const FDynamicMesh3* Mesh;
/** Input 3D Frame/Plane */
FFrame3d ProjectionFrame;
/** If true, 2D convex hull is simplified using MinEdgeLength and DeviationTolerance */
bool bSimplifyPolygon = false;
/** Minimum Edge Length of the simplified 2D Convex Hull */
double MinEdgeLength = 0.01;
/** Deviation Tolerance of the simplified 2D Convex Hull */
double DeviationTolerance = 0.1;
/** Minimum thickness of extrusion. If extrusion length is smaller than this amount, box is expanded symmetrically */
double MinThickness = 0.0;
/** Calculated convex hull polygon */
FPolygon2d ConvexHull2D;
/** Simplified convex hull polygon. Not initialized if bSimplifyPolygon == false */
FPolygon2d SimplifiedHull2D;
/** Output swept-polygon convex hull */
FDynamicMesh3 ConvexHull3D;
enum class EKeep3DHullSide : uint8
{
// Both sides of the projection hull will be flat
None,
// The front of the projection hull will follow the 3D convex hull, and the back will be flat
Front,
// The back of the projection hull will follow the 3D convex hull, and the front will be flat
Back
// Note: If both the front and back follow the 3D hull, that is just a regular convex hull; see MeshConvexHull.h
};
/** Whether to conform to the 3D convex hull surface on the front or back side of the sweep, or to use a flat surface on both sides of the swept hull */
EKeep3DHullSide Keep3DHullSide = EKeep3DHullSide::None;
public:
FMeshProjectionHull(const FDynamicMesh3* MeshIn)
{
Mesh = MeshIn;
}
/**
* Calculate output 2D Convex Polygon and Swept-Polygon 3D Mesh for vertices of input Mesh
* @return true on success
*/
UE_API bool Compute();
private:
// Helper to compute the 3D hull when Keep3DHullSide is not None; called by Compute after the 2D projection hull is computed
UE_API bool ComputeWith3DHullSide(FFrame3d CenterFrame, double ExtrudeLength);
};
} // end namespace UE::Geometry
} // end namespace UE
#undef UE_API