TGeoTessellated.cxx

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// @(#)root/geom:$Id$// Author: Andrei Gheata   24/10/01
 
// Contains() and DistFromOutside/Out() implemented by Mihaela Gheata
 
/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
/** \class TGeoTessellated
\ingroup Geometry_classes
 
Tessellated solid class. It is composed by a set of planar faces having triangular or
quadrilateral shape. The class does not provide navigation functionality, it just wraps the data
for the composing faces.
*/
 
#include <iostream>
#include <sstream>
 
#include "TGeoManager.h"
#include "TGeoMatrix.h"
#include "TGeoVolume.h"
#include "TVirtualGeoPainter.h"
#include "TGeoTessellated.h"
#include "TBuffer3D.h"
#include "TBuffer3DTypes.h"
#include "TMath.h"
 
#include <array>
#include <vector>
 
ClassImp(TGeoTessellated)
 
   using Vertex_t = Tessellated::Vertex_t;
 
std::ostream &operator<<(std::ostream &os, TGeoFacet const &facet)
{
   os << "{";
   for (int i = 0; i < facet.GetNvert(); ++i) {
      os << facet.GetVertex(i);
      if (i != facet.GetNvert() - 1)
         os << ", ";
   }
   os << "}";
   return os;
}
 
TGeoFacet::TGeoFacet(const TGeoFacet &other) : fVertices(other.fVertices), fNvert(other.fNvert), fShared(other.fShared)
{
   memcpy(fIvert, other.fIvert, 4 * sizeof(int));
   if (!fShared && other.fVertices)
      fVertices = new VertexVec_t(*other.fVertices);
}
 
const TGeoFacet &TGeoFacet::operator=(const TGeoFacet &other)
{
   if (&other != this) {
      if (!fShared)
         delete fVertices;
      fNvert = other.fNvert;
      fShared = other.fShared;
      memcpy(fIvert, other.fIvert, 4 * sizeof(int));
      if (!fShared && other.fVertices)
         fVertices = new VertexVec_t(*other.fVertices);
      else
         fVertices = other.fVertices;
   }
   return *this;
}
 
Vertex_t TGeoFacet::ComputeNormal(bool &degenerated) const
{
   // Compute normal using non-zero segments
   constexpr double kTolerance = 1.e-20;
   degenerated = true;
   Vertex_t normal;
   for (int i = 0; i < fNvert - 1; ++i) {
      Vertex_t e1 = GetVertex(i + 1) - GetVertex(i);
      if (e1.Mag2() < kTolerance)
         continue;
      for (int j = i + 1; j < fNvert; ++j) {
         Vertex_t e2 = GetVertex((j + 1) % fNvert) - GetVertex(j);
         if (e2.Mag2() < kTolerance)
            continue;
         normal = Vertex_t::Cross(e1, e2);
         // e1 and e2 may be colinear
         if (normal.Mag2() < kTolerance)
            continue;
         normal.Normalize();
         degenerated = false;
         break;
      }
      if (!degenerated)
         break;
   }
   return normal;
}
 
bool TGeoFacet::Check() const
{
   constexpr double kTolerance = 1.e-10;
   bool degenerated = true;
   ComputeNormal(degenerated);
   if (degenerated) {
      std::cout << "Facet: " << *this << " is degenerated\n";
      return false;
   }
 
   // Compute surface area
   double surfaceArea = 0.;
   for (int i = 1; i < fNvert - 1; ++i) {
      Vertex_t e1 = GetVertex(i) - GetVertex(0);
      Vertex_t e2 = GetVertex(i + 1) - GetVertex(0);
      surfaceArea += 0.5 * Vertex_t::Cross(e1, e2).Mag();
   }
   if (surfaceArea < kTolerance) {
      std::cout << "Facet: " << *this << " has zero surface area\n";
      return false;
   }
 
   // Center of the tile
   /*
   Vertex_t center;
   for (int i = 0; i < fNvert; ++i)
      center += GetVertex(i);
   center /= fNvert;
   */
   return true;
}
 
int TGeoFacet::CompactFacet(Vertex_t *vert, int nvertices)
{
   // Compact the common vertices and return new facet
   if (nvertices < 2)
      return nvertices;
   int nvert = nvertices;
   int i = 0;
   while (i < nvert) {
      if (vert[(i + 1) % nvert] == vert[i]) {
         // shift last vertices left by one element
         for (int j = i + 2; j < nvert; ++j)
            vert[j - 1] = vert[j];
         nvert--;
      }
      i++;
   }
   return nvert;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Check if a connected neighbour facet has compatible normal
 
bool TGeoFacet::IsNeighbour(const TGeoFacet &other, bool &flip) const
{
 
   // Find a connecting segment
   bool neighbour = false;
   int line1[2], line2[2];
   int npoints = 0;
   for (int i = 0; i < fNvert; ++i) {
      auto ivert = GetVertexIndex(i);
      // Check if the other facet has the same vertex
      for (int j = 0; j < other.GetNvert(); ++j) {
         if (ivert == other.GetVertexIndex(j)) {
            line1[npoints] = i;
            line2[npoints] = j;
            if (++npoints == 2) {
               neighbour = true;
               bool order1 = line1[1] == line1[0] + 1;
               bool order2 = line2[1] == (line2[0] + 1) % other.GetNvert();
               flip = (order1 == order2);
               return neighbour;
            }
         }
      }
   }
   return neighbour;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor. In case nfacets is zero, it is user's responsibility to
/// call CloseShape once all faces are defined.
 
TGeoTessellated::TGeoTessellated(const char *name, int nfacets) : TGeoBBox(name, 0, 0, 0)
{
   fNfacets = nfacets;
   if (nfacets)
      fFacets.reserve(nfacets);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor providing directly the array of vertices. Facets have to be added
/// providing vertex indices rather than coordinates.
 
TGeoTessellated::TGeoTessellated(const char *name, const std::vector<Vertex_t> &vertices) : TGeoBBox(name, 0, 0, 0)
{
   fVertices = vertices;
   fNvert = fVertices.size();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Function to be called after reading tessellated volumes from the geometry file
 
void TGeoTessellated::AfterStreamer()
{
   // The pointer to the array of vertices is not streamed so update it to facets
   for (auto facet : fFacets)
      facet.SetVertices(&fVertices);
   fDefined = true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Adding a triangular facet from vertex positions in absolute coordinates
 
bool TGeoTessellated::AddFacet(const Vertex_t &pt0, const Vertex_t &pt1, const Vertex_t &pt2)
{
   if (fDefined) {
      Error("AddFacet", "Shape %s already fully defined. Not adding", GetName());
      return false;
   }
 
   Vertex_t vert[3];
   vert[0] = pt0;
   vert[1] = pt1;
   vert[2] = pt2;
   int nvert = TGeoFacet::CompactFacet(vert, 3);
   if (nvert < 3) {
      Error("AddFacet", "Triangular facet at index %d degenerated. Not adding.", GetNfacets());
      return false;
   }
   fNvert += 3;
   fNseg += 3;
   fFacets.emplace_back(pt0, pt1, pt2);
 
   if (fNfacets > 0 && GetNfacets() == fNfacets)
      CloseShape();
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Adding a triangular facet from indices of vertices
 
bool TGeoTessellated::AddFacet(int i0, int i1, int i2)
{
   if (fDefined) {
      Error("AddFacet", "Shape %s already fully defined. Not adding", GetName());
      return false;
   }
   if (fVertices.size() == 0) {
      Error("AddFacet", "Shape %s Cannot add facets by indices without vertices. Not adding", GetName());
      return false;
   }
 
   fNseg += 3;
   fFacets.emplace_back(&fVertices, 3, i0, i1, i2);
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Adding a quadrilateral facet from vertex positions in absolute coordinates
 
bool TGeoTessellated::AddFacet(const Vertex_t &pt0, const Vertex_t &pt1, const Vertex_t &pt2, const Vertex_t &pt3)
{
   if (fDefined) {
      Error("AddFacet", "Shape %s already fully defined. Not adding", GetName());
      return false;
   }
   Vertex_t vert[4];
   vert[0] = pt0;
   vert[1] = pt1;
   vert[2] = pt2;
   vert[3] = pt3;
   int nvert = TGeoFacet::CompactFacet(vert, 4);
   if (nvert < 3) {
      Error("AddFacet", "Quadrilateral facet at index %d degenerated. Not adding.", GetNfacets());
      return false;
   }
 
   fNvert += nvert;
   fNseg += nvert;
   if (nvert == 3)
      fFacets.emplace_back(vert[0], vert[1], vert[2]);
   else
      fFacets.emplace_back(vert[0], vert[1], vert[2], vert[3]);
 
   if (fNfacets > 0 && GetNfacets() == fNfacets)
      CloseShape(false);
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Adding a quadrilateral facet from indices of vertices
 
bool TGeoTessellated::AddFacet(int i0, int i1, int i2, int i3)
{
   if (fDefined) {
      Error("AddFacet", "Shape %s already fully defined. Not adding", GetName());
      return false;
   }
   if (fVertices.size() == 0) {
      Error("AddFacet", "Shape %s Cannot add facets by indices without vertices. Not adding", GetName());
      return false;
   }
 
   fNseg += 4;
   fFacets.emplace_back(&fVertices, 4, i0, i1, i2, i3);
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Close the shape: calculate bounding box and compact vertices
 
void TGeoTessellated::CloseShape(bool check, bool fixFlipped, bool verbose)
{
   // Compact the array of vertices
   constexpr double tolerance = 1.e-10;
   constexpr int ngrid = 100;
   ComputeBBox();
   double minExtent[3];
   minExtent[0] = fOrigin[0] - fDX - tolerance;
   minExtent[1] = fOrigin[1] - fDY - tolerance;
   minExtent[2] = fOrigin[2] - fDZ - tolerance;
 
   double invExtent[3];
   invExtent[0] = 0.5 / (fDX + tolerance);
   invExtent[1] = 0.5 / (fDY + tolerance);
   invExtent[2] = 0.5 / (fDZ + tolerance);
 
   if (fVertices.size() > 0) {
      fDefined = true;
      if (!check)
         return;
 
      // Check facets
      for (auto &facet : fFacets) {
         facet.Check();
      }
      fClosedBody = CheckClosure(fixFlipped, verbose);
      return;
   }
 
   auto AddVertex = [this](const Vertex_t &vertex) {
      // Check if vertex exists
      int ivert = 0;
      for (const auto &current_vert : fVertices) {
         if (current_vert == vertex)
            return ivert;
         ivert++;
      }
      // Vertex new, just add it
      fVertices.push_back(vertex);
      return ivert;
   };
 
   auto GetHashIndex = [&](const Vertex_t &vertex) {
      // Get the hash index for a vertex in a 10x10x10 grid in the bounding box
      int index = 0;
      for (int i = 0; i < 3; ++i) {
         int ind = int(ngrid * (vertex[i] - minExtent[i]) * invExtent[i]); // between [0, ngrid-1]
         assert(ind < (int)ngrid);
         for (int j = i + 1; j < 3; ++j)
            ind *= ngrid;
         index += ind;
      }
      return index;
   };
 
   // In case the number of vertices is small, just compare with all others
   int ind[4] = {-1, -1, -1, -1};
   if (fNvert < 1000) {
      for (auto &facet : fFacets) {
         int nvert = facet.GetNvert();
         for (int i = 0; i < nvert; ++i) {
            // Check if vertex exists already
            ind[i] = AddVertex(facet.GetVertex(i));
         }
         facet.SetVertices(&fVertices, nvert, ind[0], ind[1], ind[2], ind[3]);
      }
   } else {
      // Use hash index for each vertex
      using CellVec_t = std::vector<int>;
      auto grid = new std::array<CellVec_t, ngrid * ngrid * ngrid>;
      for (auto &facet : fFacets) {
         int nvert = facet.GetNvert();
         for (int i = 0; i < nvert; ++i) {
            // Check if vertex exists already
            const Vertex_t &vertex = facet.GetVertex(i);
            int hashind = GetHashIndex(vertex);
            bool isAdded = false;
            for (auto ivert : grid->operator[](hashind)) {
               if (vertex == fVertices[ivert]) {
                  ind[i] = ivert;
                  isAdded = true;
                  break;
               }
            }
            if (!isAdded) {
               fVertices.push_back(vertex);
               ind[i] = fVertices.size() - 1;
               grid->operator[](hashind).push_back(ind[i]);
            }
         }
         facet.SetVertices(&fVertices, nvert, ind[0], ind[1], ind[2], ind[3]);
      }
      delete grid;
   }
   fNvert = fVertices.size();
   fNfacets = fFacets.size();
   fDefined = true;
   if (!check)
      return;
 
   // Check facets
   for (auto &facet : fFacets) {
      facet.Check();
   }
 
   fClosedBody = CheckClosure(fixFlipped, verbose);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Check closure of the solid and check/fix flipped normals
 
bool TGeoTessellated::CheckClosure(bool fixFlipped, bool verbose)
{
   int *nn = new int[fNfacets];
   bool *flipped = new bool[fNfacets];
   bool hasorphans = false;
   bool hasflipped = false;
   for (int i = 0; i < fNfacets; ++i) {
      nn[i] = 0;
      flipped[i] = false;
   }
 
   for (int icrt = 0; icrt < fNfacets; ++icrt) {
      // all neighbours checked?
      if (nn[icrt] >= fFacets[icrt].GetNvert())
         continue;
      for (int i = icrt + 1; i < fNfacets; ++i) {
         bool isneighbour = fFacets[icrt].IsNeighbour(fFacets[i], flipped[i]);
         if (isneighbour) {
            if (flipped[icrt])
               flipped[i] = !flipped[i];
            if (flipped[i])
               hasflipped = true;
            nn[icrt]++;
            nn[i]++;
            if (nn[icrt] == fFacets[icrt].GetNvert())
               break;
         }
      }
      if (nn[icrt] < fFacets[icrt].GetNvert())
         hasorphans = true;
   }
 
   if (hasorphans && verbose) {
      Error("Check", "Tessellated solid %s has following not fully connected facets:", GetName());
      for (int icrt = 0; icrt < fNfacets; ++icrt) {
         if (nn[icrt] < fFacets[icrt].GetNvert())
            std::cout << icrt << " (" << fFacets[icrt].GetNvert() << " edges, " << nn[icrt] << " neighbours)\n";
      }
   }
   fClosedBody = !hasorphans;
   int nfixed = 0;
   if (hasflipped) {
      if (verbose)
         Warning("Check", "Tessellated solid %s has following facets with flipped normals:", GetName());
      for (int icrt = 0; icrt < fNfacets; ++icrt) {
         if (flipped[icrt]) {
            if (verbose)
               std::cout << icrt << "\n";
            if (fixFlipped) {
               fFacets[icrt].Flip();
               nfixed++;
            }
         }
      }
      if (nfixed && verbose)
         Info("Check", "Automatically flipped %d facets to match first defined facet", nfixed);
   }
   delete[] nn;
   delete[] flipped;
 
   return !hasorphans;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Compute bounding box
 
void TGeoTessellated::ComputeBBox()
{
   const double kBig = TGeoShape::Big();
   double vmin[3] = {kBig, kBig, kBig};
   double vmax[3] = {-kBig, -kBig, -kBig};
   for (const auto &facet : fFacets) {
      for (int i = 0; i < facet.GetNvert(); ++i) {
         for (int j = 0; j < 3; ++j) {
            vmin[j] = TMath::Min(vmin[j], facet.GetVertex(i).operator[](j));
            vmax[j] = TMath::Max(vmax[j], facet.GetVertex(i).operator[](j));
         }
      }
   }
   fDX = 0.5 * (vmax[0] - vmin[0]);
   fDY = 0.5 * (vmax[1] - vmin[1]);
   fDZ = 0.5 * (vmax[2] - vmin[2]);
   for (int i = 0; i < 3; ++i)
      fOrigin[i] = 0.5 * (vmax[i] + vmin[i]);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Returns numbers of vertices, segments and polygons composing the shape mesh.
 
void TGeoTessellated::GetMeshNumbers(int &nvert, int &nsegs, int &npols) const
{
   nvert = fNvert;
   nsegs = fNseg;
   npols = GetNfacets();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Creates a TBuffer3D describing *this* shape.
/// Coordinates are in local reference frame.
 
TBuffer3D *TGeoTessellated::MakeBuffer3D() const
{
   const int nvert = fNvert;
   const int nsegs = fNseg;
   const int npols = GetNfacets();
   auto buff = new TBuffer3D(TBuffer3DTypes::kGeneric, nvert, 3 * nvert, nsegs, 3 * nsegs, npols, 6 * npols);
   if (buff) {
      SetPoints(buff->fPnts);
      SetSegsAndPols(*buff);
   }
   return buff;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Prints basic info
 
void TGeoTessellated::Print(Option_t *) const
{
   std::cout << "=== Tessellated shape " << GetName() << " having " << GetNvertices() << " vertices and "
             << GetNfacets() << " facets\n";
}
 
////////////////////////////////////////////////////////////////////////////////
/// Fills TBuffer3D structure for segments and polygons.
 
void TGeoTessellated::SetSegsAndPols(TBuffer3D &buff) const
{
   const int c = GetBasicColor();
   int *segs = buff.fSegs;
   int *pols = buff.fPols;
 
   int indseg = 0; // segment internal data index
   int indpol = 0; // polygon internal data index
   int sind = 0;   // segment index
   for (const auto &facet : fFacets) {
      auto nvert = facet.GetNvert();
      pols[indpol++] = c;
      pols[indpol++] = nvert;
      for (auto j = 0; j < nvert; ++j) {
         int k = (j + 1) % nvert;
         // segment made by next consecutive points
         segs[indseg++] = c;
         segs[indseg++] = facet.GetVertexIndex(j);
         segs[indseg++] = facet.GetVertexIndex(k);
         // add segment to current polygon and increment segment index
         pols[indpol + nvert - j - 1] = sind++;
      }
      indpol += nvert;
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Fill tessellated points to an array.
 
void TGeoTessellated::SetPoints(double *points) const
{
   int ind = 0;
   for (const auto &vertex : fVertices) {
      vertex.CopyTo(&points[ind]);
      ind += 3;
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Fill tessellated points in float.
 
void TGeoTessellated::SetPoints(Float_t *points) const
{
   int ind = 0;
   for (const auto &vertex : fVertices) {
      points[ind++] = vertex.x();
      points[ind++] = vertex.y();
      points[ind++] = vertex.z();
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Resize the shape by scaling vertices within maxsize and center to origin
 
void TGeoTessellated::ResizeCenter(double maxsize)
{
   using Vector3_t = Vertex_t;
 
   if (!fDefined) {
      Error("ResizeCenter", "Not all faces are defined");
      return;
   }
   Vector3_t origin(fOrigin[0], fOrigin[1], fOrigin[2]);
   double maxedge = TMath::Max(TMath::Max(fDX, fDY), fDZ);
   double scale = maxsize / maxedge;
   for (size_t i = 0; i < fVertices.size(); ++i) {
      fVertices[i] = scale * (fVertices[i] - origin);
   }
   fOrigin[0] = fOrigin[1] = fOrigin[2] = 0;
   fDX *= scale;
   fDY *= scale;
   fDZ *= scale;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Fills a static 3D buffer and returns a reference.
 
const TBuffer3D &TGeoTessellated::GetBuffer3D(int reqSections, Bool_t localFrame) const
{
   static TBuffer3D buffer(TBuffer3DTypes::kGeneric);
 
   FillBuffer3D(buffer, reqSections, localFrame);
 
   const int nvert = fNvert;
   const int nsegs = fNseg;
   const int npols = GetNfacets();
 
   if (reqSections & TBuffer3D::kRawSizes) {
      if (buffer.SetRawSizes(nvert, 3 * nvert, nsegs, 3 * nsegs, npols, 6 * npols)) {
         buffer.SetSectionsValid(TBuffer3D::kRawSizes);
      }
   }
   if ((reqSections & TBuffer3D::kRaw) && buffer.SectionsValid(TBuffer3D::kRawSizes)) {
      SetPoints(buffer.fPnts);
      if (!buffer.fLocalFrame) {
         TransformPoints(buffer.fPnts, buffer.NbPnts());
      }
 
      SetSegsAndPols(buffer);
      buffer.SetSectionsValid(TBuffer3D::kRaw);
   }
 
   return buffer;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Reads a single tessellated solid from an .obj file.
 
TGeoTessellated *TGeoTessellated::ImportFromObjFormat(const char *objfile, bool check, bool verbose)
{
   using namespace std;
 
   vector<Vertex_t> vertices;
   vector<string> sfacets;
 
   struct FacetInd_t {
      int i0 = -1;
      int i1 = -1;
      int i2 = -1;
      int i3 = -1;
      int nvert = 0;
      FacetInd_t(int a, int b, int c)
      {
         i0 = a;
         i1 = b;
         i2 = c;
         nvert = 3;
      };
      FacetInd_t(int a, int b, int c, int d)
      {
         i0 = a;
         i1 = b;
         i2 = c;
         i3 = d;
         nvert = 4;
      };
   };
 
   vector<FacetInd_t> facets;
   // List of geometric vertices, with (x, y, z [,w]) coordinates, w is optional and defaults to 1.0.
   // struct vtx_t { double x = 0; double y = 0; double z = 0; double w = 1; };
 
   // Texture coordinates in u, [,v ,w]) coordinates, these will vary between 0 and 1. v, w are optional and default to
   // 0.
   // struct tex_t { double u; double v; double w; };
 
   // List of vertex normals in (x,y,z) form; normals might not be unit vectors.
   // struct vn_t { double x; double y; double z; };
 
   // Parameter space vertices in ( u [,v] [,w] ) form; free form geometry statement
   // struct vp_t { double u; double v; double w; };
 
   // Faces are defined using lists of vertex, texture and normal indices which start at 1.
   // Polygons such as quadrilaterals can be defined by using more than three vertex/texture/normal indices.
   //     f v1//vn1 v2//vn2 v3//vn3 ...
 
   // Records starting with the letter "l" specify the order of the vertices which build a polyline.
   //     l v1 v2 v3 v4 v5 v6 ...
 
   string line;
   int ind[4] = {0};
   ifstream file(objfile);
   if (!file.is_open()) {
      ::Error("TGeoTessellated::ImportFromObjFormat", "Unable to open %s", objfile);
      return nullptr;
   }
 
   while (getline(file, line)) {
      stringstream ss(line);
      string tag;
 
      // We ignore everything which is not a vertex or a face
      if (line.rfind("v", 0) == 0 && line.rfind("vt", 0) != 0 && line.rfind("vn", 0) != 0 && line.rfind("vn", 0) != 0) {
         // Decode the vertex
         double pos[4] = {0, 0, 0, 1};
         ss >> tag >> pos[0] >> pos[1] >> pos[2] >> pos[3];
         vertices.emplace_back(pos[0] * pos[3], pos[1] * pos[3], pos[2] * pos[3]);
      }
 
      else if (line.rfind("f", 0) == 0) {
         // Decode the face
         ss >> tag;
         string word;
         sfacets.clear();
         while (ss >> word)
            sfacets.push_back(word);
         if (sfacets.size() > 4 || sfacets.size() < 3) {
            ::Error("TGeoTessellated::ImportFromObjFormat", "Detected face having unsupported %zu vertices",
                    sfacets.size());
            return nullptr;
         }
         int nvert = 0;
         for (auto sword : sfacets) {
            stringstream ssword(sword);
            string token;
            getline(ssword, token, '/'); // just need the vertex index, which is the first token
            // Convert string token to integer
 
            ind[nvert++] = stoi(token) - 1;
            if (ind[nvert - 1] < 0) {
               ::Error("TGeoTessellated::ImportFromObjFormat", "Unsupported relative vertex index definition in %s",
                       objfile);
               return nullptr;
            }
         }
         if (nvert == 3)
            facets.emplace_back(ind[0], ind[1], ind[2]);
         else
            facets.emplace_back(ind[0], ind[1], ind[2], ind[3]);
      }
   }
 
   int nvertices = (int)vertices.size();
   int nfacets = (int)facets.size();
   if (nfacets < 3) {
      ::Error("TGeoTessellated::ImportFromObjFormat", "Not enough faces detected in %s", objfile);
      return nullptr;
   }
 
   string sobjfile(objfile);
   if (verbose)
      std::cout << "Read " << nvertices << " vertices and " << nfacets << " facets from " << sobjfile << endl;
 
   auto tsl = new TGeoTessellated(sobjfile.erase(sobjfile.find_last_of('.')).c_str(), vertices);
 
   for (int i = 0; i < nfacets; ++i) {
      auto facet = facets[i];
      if (facet.nvert == 3)
         tsl->AddFacet(facet.i0, facet.i1, facet.i2);
      else
         tsl->AddFacet(facet.i0, facet.i1, facet.i2, facet.i3);
   }
   tsl->CloseShape(check, true, verbose);
   tsl->Print();
   return tsl;
}