Tribox.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Chaos/Core.h"
#include "Chaos/Convex.h"
 
namespace Chaos
{
namespace Private
{
        
class FTribox
{
public :
 
    using FRealType = FRealSingle;
    using FVec3Type = TVec3<FRealType>;
    using FRigidTransform3Type = TRigidTransform<FRealType, 3>;
    using FMatrix33Type = PMatrix<FRealType, 3, 3>;
    using FPlaneType = TPlaneConcrete<FRealType, 3>;
 
    // Number of planes that will be used to define the Tribox 
    static constexpr int32 NumPlanes = 18;
 
    // Number of principal planes
    static constexpr int32 NumPrincipalPlanes = 6;
 
    // Number of chamfer planes
    static constexpr int32 NumChamferPlanes = 12;
 
    // Distance used to inflate the Tribox to avoid degenerate case
    static constexpr FRealType InflateDistance = 0.5;
 
    // Base Constructor
    FORCEINLINE FTribox() : MaxDists(), bIsValid(false), bHasDatas(false)
    {
        for(int32 DistsIndex = 0; DistsIndex< NumPlanes; ++DistsIndex)
        {
            MaxDists[DistsIndex] = TNumericLimits<FRealType>::Lowest();
        }
    };
 
    // Base Constructor
    FORCEINLINE FTribox(const FTribox& OtherTribox) : MaxDists(), bIsValid(false), bHasDatas(false)
    {
        for(int32 DistsIndex = 0; DistsIndex < NumPlanes; ++DistsIndex)
        {
            MaxDists[DistsIndex] = OtherTribox.MaxDists[DistsIndex];
        }
        bIsValid = OtherTribox.bIsValid;
        bHasDatas = OtherTribox.bHasDatas;
    };
    
    // Get the tribox center
    FVec3Type GetCenter() const;
 
    // Get the bounding box
    FAABB3 GetBounds() const;
    
    // Get the closest plane along the +X,-X,+Y,-Y,+Z,-Z directions
    FRealType GetClosestPlane(const FVec3Type& PointPosition, int32& PlaneAxis, FRealType& PlaneProjection) const;
 
    // Add a point position to the Tribox
    void AddPoint(const FVec3Type& PointPosition);
 
    // Add convex vertices to a tribox
    void AddConvex(const FConvex* Convex, const FRigidTransform3Type& RelativeTransform);
 
    // Inflate + Scale the Max distances
    bool BuildTribox();
 
    // Find the overlapping tribox 
    bool OverlapTribox(const FTribox& OtherTribox, FTribox& OverlapTribox) const;
 
    // Check if the tribox is overlapping or not
    bool IsTriboxOverlapping(const FTribox& OtherTribox) const;
 
    // Split the tribox in 2 along a defined cuttng plane
    bool SplitTriboxSlab(const int32 PlaneAxis, const FRealType& PlaneDistance,
                    FTribox& LeftTribox, FTribox& RightTribox) const;
 
    // Get the thickest tribox slab
    int32 GetThickestSlab() const;
 
    // Sample a point along the plane direction in betwen min and max
    FRealType SampleSlabPoint(const int32 PlaneAxis, const FRealType& LocalDistance) const;
 
    // Compute the tribox volume
    FRealType ComputeVolume() const;
 
    // Create a convex from the Tribox
    FImplicitObjectPtr MakeConvex() const;
 
    // Add a tribox to this and return this
    FTribox& operator+=(const FTribox& OtherTribox);
 
    // Add a tribox to this and return a new one
    FTribox operator+( const FTribox& OtherTribox) const;
 
    // Check ihe tribox is valid
    bool IsValid() const {return bIsValid;}
 
    // Set the valid flag
    void SetValid(const bool bValid) {bIsValid = bValid;}
 
    // Check ihe tribox have been built with datas
    bool HasDatas() const {return bHasDatas;}
 
    // Reset the tribox max distances
    void ResetDists()
    {
        for(int32 DistsIndex = 0; DistsIndex< NumPlanes; ++DistsIndex)
        {
            MaxDists[DistsIndex] = TNumericLimits<FRealType>::Lowest();
        }
    }
 
private : 
    // Solve the intersection point position
    FVec3 SolveIntersection(const int32 FaceIndex[3], const FMatrix33Type& A) const;
 
    // Add the intersection point to the list of faces/vertices
    void AddIntersection(const int32 FaceIndex[3], const int32 FaceOrder[3], const FVec3Type& VertexPosition, TArray<TArray<int32>>& FaceIndices, TArray<FConvex::FVec3Type>& ConvexVertices) const;
 
    // Solve and add the intersection point in between the 3 planes
    void ComputeIntersection(const int32 CornerIndex, const int32 PrincipalIndex, const int32 ChamferIndex, TArray<TArray<int32>>& FaceIndices, TArray<FConvex::FVec3Type>& ConvexVertices) const;
 
    // Build the max dist along the principal axis
    void BuildPrincipalDist(const FVec3Type& P, const int32 CoordIndexA, const int32 DistsIndexA, const int32 DistsIndexB);
 
    // Build the max dist along the chamfer axis
    void BuildChamferDist(const FVec3Type& P, const int32 CoordIndexA, const int32 CoordIndexB,
            const int32 DistsIndexA, const int32 DistsIndexB, const int32 DistsIndexC, const int32 DistsIndexD);
 
    // Create a FConvex from a list of convex planes, face indices and convex vertices
    FImplicitObjectPtr CreateConvexFromTopology(TArray<FConvex::FPlaneType>&& ConvexPlanes,
        TArray<TArray<int32>>&& FaceIndices, TArray<FConvex::FVec3Type>&& ConvexVertices) const;
 
    // Max distance along eaxh tribox axis (principal + chamfer)
    FRealType MaxDists[NumPlanes] = {TNumericLimits<FRealType>::Lowest(), TNumericLimits<FRealType>::Lowest(),
                                     TNumericLimits<FRealType>::Lowest(), TNumericLimits<FRealType>::Lowest(),
                                     TNumericLimits<FRealType>::Lowest(), TNumericLimits<FRealType>::Lowest(),
                                     TNumericLimits<FRealType>::Lowest(), TNumericLimits<FRealType>::Lowest(),
                                     TNumericLimits<FRealType>::Lowest()};
 
    // Boolean to specify if the tribox is valid or not 
    bool bIsValid = false;
 
    // Boolean to specify if the tribox has been built with datas or not
    bool bHasDatas = false;
};
 
}
}