G4BoundingEnvelope.hh

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//
// class G4BoundingEnvelope
//
// Class description:
//
// Helper class to facilitate calculation of the extent of a solid
// within the limits defined by a G4VoxelLimits object.
//
// The function CalculateExtent() of a particular solid can create
// a G4BoundingEnvelope object that bounds the solid and then call
// CalculateExtent() of the G4BoundingEnvelope object.
//
// Calculation of extent uses G4Transform3D, thus takes into account
// scaling and reflection, if any.

// 2016.05.25,  E.Tcherniaev - initial version
// --------------------------------------------------------------------
#ifndef G4BOUNDINGENVELOPE_HH
#define G4BOUNDINGENVELOPE_HH

#include <vector>
#include "geomdefs.hh"

#include "G4ThreeVector.hh"
#include "G4VoxelLimits.hh"
#include "G4Transform3D.hh"
#include "G4Point3D.hh"
#include "G4Plane3D.hh"

using G4ThreeVectorList = std::vector<G4ThreeVector>;
using G4Polygon3D = std::vector<G4Point3D>;
using G4Segment3D = std::pair<G4Point3D,G4Point3D>;

class G4BoundingEnvelope
{
  public:

    G4BoundingEnvelope(const G4ThreeVector& pMin,
                       const G4ThreeVector& pMax);
      // Constructor from an axis aligned bounding box (AABB)

    G4BoundingEnvelope(const std::vector<const G4ThreeVectorList*>& polygons);
      // Constructor from a sequence of convex polygons, the polygons
      // should have equal numbers of vertices except first and last
      // polygons which may consist of a single vertex

    G4BoundingEnvelope(const G4ThreeVector& pMin, 
                       const G4ThreeVector& pMax,
                       const std::vector<const G4ThreeVectorList*>& polygons);
      // Constructor from AABB and a sequence of polygons

    ~G4BoundingEnvelope();
      // Destructor

    G4bool BoundingBoxVsVoxelLimits(const EAxis pAxis,
                                    const G4VoxelLimits& pVoxelLimits,
                                    const G4Transform3D& pTransform3D,
                                    G4double& pMin, G4double& pMax) const;
      // Analyse the position of the bounding box relative to the voxel.
      // It returns "true" in the case where the value of the extent can be
      // figured out directly from the dimensions of the bounding box, or
      // it is clear that the bounding box and the voxel do not intersect.
      // The reply "false" means that further calculations are needed.

    G4bool CalculateExtent(const EAxis pAxis,
                           const G4VoxelLimits& pVoxelLimits,
                           const G4Transform3D& pTransform3D,
                           G4double& pMin, G4double& pMax) const;
      // Calculate extent of the bounding envelope

  private:

    void CheckBoundingBox();
      // Check correctness of the AABB (axis aligned bounding box)

    void CheckBoundingPolygons();
      // Check correctness of the sequence of convex polygonal bases

    G4double FindScaleFactor(const G4Transform3D& pTransform3D) const;
      // Find max scale factor of the transformation

    void TransformVertices(const G4Transform3D& pTransform3D,
                                 std::vector<G4Polygon3D*>& pBases) const;
      // Create list of transformed polygons

    void GetPrismAABB(const G4Polygon3D& pBaseA,
                      const G4Polygon3D& pBaseB,
                            G4Segment3D& pAABB) const;
      // Find bounding box of a prism

    void CreateListOfEdges(const G4Polygon3D& baseA,
                           const G4Polygon3D& baseB,
                                 std::vector<G4Segment3D>& pEdges) const;
      // Create list of edges of a prism
  
    void CreateListOfPlanes(const G4Polygon3D& baseA,
                            const G4Polygon3D& baseB,
                                  std::vector<G4Plane3D>& pPlanes) const;
      // Create list of planes bounding a prism

    G4bool ClipEdgesByVoxel(const std::vector<G4Segment3D>& pEdges,
                            const G4VoxelLimits& pLimits,
                                  G4Segment3D& pExtent) const;
      // Clip set of edges by G4VoxelLimits

    void ClipVoxelByPlanes(G4int pBits,
                           const G4VoxelLimits& pLimits,
                           const std::vector<G4Plane3D>& pPlanes,
                           const G4Segment3D& pAABB,
                                 G4Segment3D& pExtent) const;
      // Clip G4VoxelLimits by set of planes bounding a prism

  private:

    G4ThreeVector fMin, fMax; 
      // original bounding box

    const std::vector<const G4ThreeVectorList*>* fPolygons = nullptr;
      // ref to original sequence of polygonal bases
};

#endif // G4BOUNDINGENVELOPE_HH