/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkPicker.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include "vtkPicker.h"

#include "vtkActor.h"
#include "vtkAssemblyNode.h"
#include "vtkAssemblyPath.h"
#include "vtkCamera.h"
#include "vtkCommand.h"
#include "vtkCompositeDataSet.h"
#include "vtkCompositeDataIterator.h"
#include "vtkImageData.h"
#include "vtkLODProp3D.h"
#include "vtkMapper.h"
#include "vtkMath.h"
#include "vtkObjectFactory.h"
#include "vtkPoints.h"
#include "vtkProp3DCollection.h"
#include "vtkProperty.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"
#include "vtkTransform.h"
#include "vtkVertex.h"
#include "vtkVolume.h"
#include "vtkAbstractVolumeMapper.h"
#include "vtkImageMapper3D.h"
#include "vtkBox.h"
#include "vtkImageSlice.h"

vtkStandardNewMacro(vtkPicker);

//----------------------------------------------------------------------
// Construct object with initial tolerance of 1/40th of window. There are no
// pick methods and picking is performed from the renderer's actors.
vtkPicker::vtkPicker()
{
  this->Tolerance = 0.025; // 1/40th of the renderer window

  this->MapperPosition[0] = 0.0;
  this->MapperPosition[1] = 0.0;
  this->MapperPosition[2] = 0.0;

  this->Mapper = nullptr;
  this->DataSet = nullptr;
  this->CompositeDataSet = nullptr;
  this->FlatBlockIndex = -1;
  this->GlobalTMin = VTK_DOUBLE_MAX;
  this->Actors = vtkActorCollection::New();
  this->Prop3Ds = vtkProp3DCollection::New();
  this->PickedPositions = vtkPoints::New();
  this->Transform = vtkTransform::New();
}

//----------------------------------------------------------------------
vtkPicker::~vtkPicker()
{
  this->Actors->Delete();
  this->Prop3Ds->Delete();
  this->PickedPositions->Delete();
  this->Transform->Delete();
}

//----------------------------------------------------------------------
// Update state when prop3D is picked.
void vtkPicker::MarkPicked(vtkAssemblyPath *path,
                           vtkProp3D *vtkNotUsed(prop3D),
                           vtkAbstractMapper3D *m,
                           double tMin, double mapperPos[3])
{
  vtkMapper *mapper;
  vtkAbstractVolumeMapper *volumeMapper;
  vtkImageMapper3D *imageMapper;

  if ( (mapper=vtkMapper::SafeDownCast(m)) != nullptr)
  {
    this->MarkPickedData(path, tMin, mapperPos, mapper, mapper->GetInput());
  }
  else if ( (volumeMapper=vtkAbstractVolumeMapper::SafeDownCast(m)) != nullptr )
  {
    this->MarkPickedData(path, tMin, mapperPos,
                         volumeMapper, volumeMapper->GetDataSetInput());
  }
  else if ( (imageMapper=vtkImageMapper3D::SafeDownCast(m)) != nullptr )
  {
    this->MarkPickedData(path, tMin, mapperPos,
                         imageMapper, imageMapper->GetInput());
  }
  else
  {
    this->MarkPickedData(path, tMin, mapperPos, nullptr, nullptr);
  }
}

void vtkPicker::MarkPickedData(vtkAssemblyPath* path,
                               double tMin, double mapperPos[3],
                               vtkAbstractMapper3D* mapper,
                               vtkDataSet* input, vtkIdType flatIndex)
{
  this->SetPath(path);
  this->GlobalTMin = tMin;

  for (int i=0; i < 3; i++)
  {
    this->MapperPosition[i] = mapperPos[i];
  }
  // The point has to be transformed back into world coordinates.
  // Note: it is assumed that the transform is in the correct state.
  this->Transform->TransformPoint(mapperPos, this->PickPosition);

  this->Mapper = mapper;
  this->DataSet = input;
  this->CompositeDataSet =
      vtkCompositeDataSet::SafeDownCast(mapper->GetInputDataObject(0,0));
  this->FlatBlockIndex = flatIndex;
}

int vtkPicker::Pick3DPoint(
  double pos[3],
  vtkRenderer *renderer)
{
  int i;
  vtkProp *prop;
  vtkAbstractMapper3D *mapper = nullptr;
  int winSize[2] = {1, 1};
  double x, y;
  double *viewport;
  int pickable;
  int LODId;
  double windowLowerLeft[4], windowUpperRight[4];
  double bounds[6], tol;
  vtkActor *actor;
  vtkLODProp3D *prop3D;
  vtkVolume *volume;
  vtkImageSlice *imageSlice = 0;
  vtkAssemblyPath *path;
  vtkProperty *tempProperty;
  vtkCollectionSimpleIterator pit;

  //  Initialize picking process
  this->Initialize();
  this->Renderer = renderer;

  // Invoke start pick method if defined
  this->InvokeEvent(vtkCommand::StartPickEvent,nullptr);

  bounds[0] = bounds[1] = bounds[2] = bounds[3] = bounds[4] = bounds[5] = 0;

  // Compute the tolerance in world coordinates.  Do this by
  // determining the world coordinates of the diagonal points of the
  // window, computing the width of the window in world coordinates, and
  // multiplying by the tolerance.
  //
  viewport = renderer->GetViewport();
  if (renderer->GetRenderWindow())
  {
    int *winSizePtr = renderer->GetRenderWindow()->GetSize();
    if (winSizePtr)
    {
      winSize[0] = winSizePtr[0];
      winSize[1] = winSizePtr[1];
    }
  }
  x = winSize[0] * viewport[0];
  y = winSize[1] * viewport[1];
  renderer->SetDisplayPoint(x, y, 0.0);
  renderer->DisplayToWorld();
  renderer->GetWorldPoint(windowLowerLeft);

  x = winSize[0] * viewport[2];
  y = winSize[1] * viewport[3];
  renderer->SetDisplayPoint(x, y, 0.0);
  renderer->DisplayToWorld();
  renderer->GetWorldPoint(windowUpperRight);

  for (tol=0.0,i=0; i<3; i++)
  {
    tol += (windowUpperRight[i] - windowLowerLeft[i]) *
      (windowUpperRight[i] - windowLowerLeft[i]);
  }

  tol = sqrt (tol) * this->Tolerance;

  //  Loop over all props.  Transform ray (defined from position of
  //  camera to selection point) into coordinates of mapper (not
  //  transformed to actors coordinates!  Reduces overall computation!!!).
  //  Note that only vtkProp3D's can be picked by vtkPicker.
  //
  vtkPropCollection *props;
  vtkProp *propCandidate;
  if ( this->PickFromList )
  {
    props = this->GetPickList();
  }
  else
  {
    props = renderer->GetViewProps();
  }

  for ( props->InitTraversal(pit); (prop=props->GetNextProp(pit)); )
  {
    for ( prop->InitPathTraversal(); (path=prop->GetNextPath()); )
    {
      pickable = 0;
      actor = nullptr;
      propCandidate = path->GetLastNode()->GetViewProp();
      if ( propCandidate->GetPickable() && propCandidate->GetVisibility() )
      {
        pickable = 1;
        if ( (actor=vtkActor::SafeDownCast(propCandidate)) != nullptr )
        {
          mapper = actor->GetMapper();
          if ( actor->GetProperty()->GetOpacity() <= 0.0 )
          {
            pickable = 0;
          }
        }
        else if ( (prop3D=vtkLODProp3D::SafeDownCast(propCandidate)) != nullptr )
        {
          LODId = prop3D->GetPickLODID();
          mapper = prop3D->GetLODMapper(LODId);

          // if the mapper is a vtkMapper (as opposed to a vtkVolumeMapper),
          // then check the transparency to see if the object is pickable
          if ( vtkMapper::SafeDownCast(mapper) != nullptr)
          {
            prop3D->GetLODProperty(LODId, &tempProperty);
            if ( tempProperty->GetOpacity() <= 0.0 )
            {
              pickable = 0;
            }
          }
        }
        else if ( (volume=vtkVolume::SafeDownCast(propCandidate)) != nullptr )
        {
          mapper = volume->GetMapper();
        }
        else if ( (imageSlice=vtkImageSlice::SafeDownCast(propCandidate)) )
        {
          mapper = imageSlice->GetMapper();
        }
        else
        {
          pickable = 0; //only vtkProp3D's (actors and volumes) can be picked
        }
      }

      //  If actor can be picked, get its composite matrix, invert it, and
      //  use the inverted matrix to transform the points into mapper
      //  coordinates.
      if ( pickable )
      {
        const double *bnds = propCandidate->GetBounds();
        if (bnds)
        {
          bounds[0] = bnds[0] - tol; bounds[1] = bnds[1] + tol;
          bounds[2] = bnds[2] - tol; bounds[3] = bnds[3] + tol;
          bounds[4] = bnds[4] - tol; bounds[5] = bnds[5] + tol;
          if (pos[0] >= bounds[0] && pos[0] <= bounds[1] &&
              pos[1] >= bounds[2] && pos[1] <= bounds[3] &&
              pos[2] >= bounds[4] && pos[2] <= bounds[5])
          {
            this->MarkPicked(path, static_cast<vtkProp3D *>(propCandidate),
              mapper, 0.0, pos);

            // The IsItemPresent method returns "index+1"
            int prevIndex = this->Prop3Ds->IsItemPresent(prop)-1;

            if (prevIndex < 0)
            {
              this->Prop3Ds->AddItem(static_cast<vtkProp3D *>(prop));

              this->PickedPositions->InsertNextPoint(pos);

              // backwards compatibility: also add to this->Actors
              if (actor)
              {
                this->Actors->AddItem(actor);
              }
            }
          }
        }
      }//if visible and pickable and not transparent
    }//for all parts
  }//for all actors

  int picked = 0;

  if (this->Path)
  {
    // Invoke pick method if one defined - prop goes first
    this->Path->GetFirstNode()->GetViewProp()->Pick();
    this->InvokeEvent(vtkCommand::PickEvent,nullptr);
    picked = 1;
  }

  // Invoke end pick method if defined
  this->InvokeEvent(vtkCommand::EndPickEvent,nullptr);

  return picked;
}


//----------------------------------------------------------------------
// Perform pick operation with selection point provided. Normally the
// first two values for the selection point are x-y pixel coordinate, and
// the third value is =0. Return non-zero if something was successfully picked.
int vtkPicker::Pick(double selectionX, double selectionY, double selectionZ,
                    vtkRenderer *renderer)
{
  int i;
  vtkCamera *camera;
  double cameraPos[4], cameraFP[4];
  double *displayCoords, *worldCoords;
  double ray[3], rayLength;
  double tF, tB;
  double cameraDOP[3];
  double p1World[4], p2World[4];
  double *clipRange;

  //  Initialize picking process
  this->Initialize();
  this->Renderer = renderer;
  this->SelectionPoint[0] = selectionX;
  this->SelectionPoint[1] = selectionY;
  this->SelectionPoint[2] = selectionZ;

  // Invoke start pick method if defined
  this->InvokeEvent(vtkCommand::StartPickEvent,nullptr);

  if ( renderer == nullptr )
  {
    vtkErrorMacro(<<"Must specify renderer!");
    return 0;
  }

  // Get camera focal point and position. Convert to display (screen)
  // coordinates. We need a depth value for z-buffer.
  //
  camera = renderer->GetActiveCamera();
  camera->GetPosition(cameraPos);
  cameraPos[3] = 1.0;
  camera->GetFocalPoint(cameraFP);
  cameraFP[3] = 1.0;

  renderer->SetWorldPoint(cameraFP[0],cameraFP[1],cameraFP[2],cameraFP[3]);
  renderer->WorldToDisplay();
  displayCoords = renderer->GetDisplayPoint();
  selectionZ = displayCoords[2];

  // Convert the selection point into world coordinates.
  //
  renderer->SetDisplayPoint(selectionX, selectionY, selectionZ);
  renderer->DisplayToWorld();
  worldCoords = renderer->GetWorldPoint();
  if ( worldCoords[3] == 0.0 )
  {
    vtkErrorMacro(<<"Bad homogeneous coordinates");
    return 0;
  }
  for (i=0; i < 3; i++)
  {
    this->PickPosition[i] = worldCoords[i] / worldCoords[3];
  }

  //  Compute the ray endpoints.  The ray is along the line running from
  //  the camera position to the selection point, starting where this line
  //  intersects the front clipping plane, and terminating where this
  //  line intersects the back clipping plane.
  for (i=0; i<3; i++)
  {
    ray[i] = this->PickPosition[i] - cameraPos[i];
  }
  for (i=0; i<3; i++)
  {
    cameraDOP[i] = cameraFP[i] - cameraPos[i];
  }

  vtkMath::Normalize(cameraDOP);

  if (( rayLength = vtkMath::Dot(cameraDOP,ray)) == 0.0 )
  {
    vtkWarningMacro("Cannot process points");
    return 0;
  }

  clipRange = camera->GetClippingRange();

  if ( camera->GetParallelProjection() )
  {
    tF = clipRange[0] - rayLength;
    tB = clipRange[1] - rayLength;
    for (i=0; i<3; i++)
    {
      p1World[i] = this->PickPosition[i] + tF*cameraDOP[i];
      p2World[i] = this->PickPosition[i] + tB*cameraDOP[i];
    }
  }
  else
  {
    tF = clipRange[0] / rayLength;
    tB = clipRange[1] / rayLength;
    for (i=0; i<3; i++)
    {
      p1World[i] = cameraPos[i] + tF*ray[i];
      p2World[i] = cameraPos[i] + tB*ray[i];
    }
  }
  p1World[3] = p2World[3] = 1.0;



  int result = this->Pick3DInternal(renderer, p1World, p2World);

  // Invoke end pick method if defined
  this->InvokeEvent(vtkCommand::EndPickEvent,nullptr);

  return result;
}

int vtkPicker::Pick3DRay(
  double pos[3],
  double wori[4],
  vtkRenderer *renderer)
{
  //  Initialize picking process
  this->Initialize();
  this->Renderer = renderer;

  double wp1[4], wp2[4];

  double dist = renderer->GetActiveCamera()->GetClippingRange()[1];

  vtkNew<vtkTransform> trans;
  trans->RotateWXYZ(wori[0], wori[1], wori[2], wori[3]);
  double* rayDirection = trans->TransformDoubleVector(0.0, 0.0, -1.0);

  for (int i=0; i < 3; i++)
  {
    this->PickPosition[i] = pos[i];
    wp1[i] = pos[i];
    wp2[i] = pos[i] + dist * rayDirection[i];
  }

  // Invoke start pick method if defined
  this->InvokeEvent(vtkCommand::StartPickEvent,nullptr);

  wp1[3] = 1.0;
  wp2[3] = 1.0;

  int result = this->Pick3DInternal(renderer, wp1, wp2);

  // Invoke end pick method if defined
  this->InvokeEvent(vtkCommand::EndPickEvent,nullptr);

  return result;
}


int vtkPicker::Pick3DInternal(vtkRenderer *renderer, double p1World[4], double p2World[4])
{
  int i;
  vtkProp *prop;
  vtkAbstractMapper3D *mapper = nullptr;
  double p1Mapper[4], p2Mapper[4];
  int winSize[2] = {1, 1};
  double x, y, t;
  double *viewport;
  double ray[3];
  int pickable;
  int LODId;
  double windowLowerLeft[4], windowUpperRight[4];
  double bounds[6], tol;
  double hitPosition[3];

  bounds[0] = bounds[1] = bounds[2] = bounds[3] = bounds[4] = bounds[5] = 0;


  if ( renderer == nullptr )
  {
    vtkErrorMacro(<<"Must specify renderer!");
    return 0;
  }

  // Compute the tolerance in world coordinates.  Do this by
  // determining the world coordinates of the diagonal points of the
  // window, computing the width of the window in world coordinates, and
  // multiplying by the tolerance.
  //
  renderer->SetWorldPoint(
    0.5*(p1World[0] + p2World[0]),
    0.5*(p1World[1] + p2World[1]),
    0.5*(p1World[2] + p2World[2]),
    1.0);
  renderer->WorldToDisplay();
  double *displayCoords = renderer->GetDisplayPoint();
  double tolZ = displayCoords[2];

  viewport = renderer->GetViewport();
  if (renderer->GetRenderWindow())
  {
    int *winSizePtr = renderer->GetRenderWindow()->GetSize();
    if (winSizePtr)
    {
      winSize[0] = winSizePtr[0];
      winSize[1] = winSizePtr[1];
    }
  }
  x = winSize[0] * viewport[0];
  y = winSize[1] * viewport[1];
  renderer->SetDisplayPoint(x, y, tolZ);
  renderer->DisplayToWorld();
  renderer->GetWorldPoint(windowLowerLeft);

  x = winSize[0] * viewport[2];
  y = winSize[1] * viewport[3];
  renderer->SetDisplayPoint(x, y, tolZ);
  renderer->DisplayToWorld();
  renderer->GetWorldPoint(windowUpperRight);

  for (tol=0.0,i=0; i<3; i++)
  {
    tol += (windowUpperRight[i] - windowLowerLeft[i]) *
      (windowUpperRight[i] - windowLowerLeft[i]);
  }

  tol = sqrt (tol) * this->Tolerance;

  //  Loop over all props.  Transform ray (defined from position of
  //  camera to selection point) into coordinates of mapper (not
  //  transformed to actors coordinates!  Reduces overall computation!!!).
  //  Note that only vtkProp3D's can be picked by vtkPicker.
  //
  vtkPropCollection *props;
  vtkProp *propCandidate;
  if ( this->PickFromList )
  {
    props = this->GetPickList();
  }
  else
  {
    props = renderer->GetViewProps();
  }

  vtkActor *actor;
  vtkLODProp3D *prop3D;
  vtkVolume *volume;
  vtkImageSlice *imageSlice = nullptr;
  vtkAssemblyPath *path;
  vtkProperty *tempProperty;
  this->Transform->PostMultiply();
  vtkCollectionSimpleIterator pit;
  double scale[3];
  for ( props->InitTraversal(pit); (prop=props->GetNextProp(pit)); )
  {
    for ( prop->InitPathTraversal(); (path=prop->GetNextPath()); )
    {
      pickable = 0;
      actor = nullptr;
      propCandidate = path->GetLastNode()->GetViewProp();
      if ( propCandidate->GetPickable() && propCandidate->GetVisibility() )
      {
        pickable = 1;
        if ( (actor=vtkActor::SafeDownCast(propCandidate)) != nullptr )
        {
          mapper = actor->GetMapper();
          if ( actor->GetProperty()->GetOpacity() <= 0.0 )
          {
            pickable = 0;
          }
        }
        else if ( (prop3D=vtkLODProp3D::SafeDownCast(propCandidate)) != nullptr )
        {
          LODId = prop3D->GetPickLODID();
          mapper = prop3D->GetLODMapper(LODId);

          // if the mapper is a vtkMapper (as opposed to a vtkVolumeMapper),
          // then check the transparency to see if the object is pickable
          if ( vtkMapper::SafeDownCast(mapper) != nullptr)
          {
            prop3D->GetLODProperty(LODId, &tempProperty);
            if ( tempProperty->GetOpacity() <= 0.0 )
            {
              pickable = 0;
            }
          }
        }
        else if ( (volume=vtkVolume::SafeDownCast(propCandidate)) != nullptr )
        {
          mapper = volume->GetMapper();
        }
        else if ( (imageSlice=vtkImageSlice::SafeDownCast(propCandidate)) )
        {
          mapper = imageSlice->GetMapper();
        }
        else
        {
          pickable = 0; //only vtkProp3D's (actors and volumes) can be picked
        }
      }

      //  If actor can be picked, get its composite matrix, invert it, and
      //  use the inverted matrix to transform the ray points into mapper
      //  coordinates.
      if ( pickable )
      {
        vtkMatrix4x4 *lastMatrix = path->GetLastNode()->GetMatrix();
        if (lastMatrix == nullptr)
        {
          vtkErrorMacro (<< "Pick: Null matrix.");
          return 0;
        }
        this->Transform->SetMatrix(lastMatrix);
        this->Transform->Push();
        this->Transform->Inverse();
        this->Transform->GetScale(scale); //need to scale the tolerance

        this->Transform->TransformPoint(p1World,p1Mapper);
        this->Transform->TransformPoint(p2World,p2Mapper);

        for (i=0; i<3; i++)
        {
          ray[i] = p2Mapper[i] - p1Mapper[i];
        }

        this->Transform->Pop();

        //  Have the ray endpoints in mapper space, now need to compare this
        //  with the mapper bounds to see whether intersection is possible.
        //
        //  Get the bounding box of the modeller.  Note that the tolerance is
        //  added to the bounding box to make sure things on the edge of the
        //  bounding box are picked correctly.
        if ( mapper != nullptr )
        {
          mapper->GetBounds(bounds);
        }

        bounds[0] -= tol; bounds[1] += tol;
        bounds[2] -= tol; bounds[3] += tol;
        bounds[4] -= tol; bounds[5] += tol;

        if ( vtkBox::IntersectBox(bounds, p1Mapper, ray, hitPosition, t) )
        {
          t = this->IntersectWithLine(
            p1Mapper, p2Mapper, tol*0.333*(scale[0]+scale[1]+scale[2]),
            path, static_cast<vtkProp3D *>(propCandidate), mapper);

          if ( t < VTK_DOUBLE_MAX )
          {
            double p[3];
            p[0] = (1.0 - t)*p1World[0] + t*p2World[0];
            p[1] = (1.0 - t)*p1World[1] + t*p2World[1];
            p[2] = (1.0 - t)*p1World[2] + t*p2World[2];

            // The IsItemPresent method returns "index+1"
            int prevIndex = this->Prop3Ds->IsItemPresent(prop)-1;

            if (prevIndex >= 0)
            {
              // If already in list, set point to the closest point
              double oldp[3];
              this->PickedPositions->GetPoint(prevIndex, oldp);
              if (vtkMath::Distance2BetweenPoints(p1World, p) <
                  vtkMath::Distance2BetweenPoints(p1World, oldp))
              {
                this->PickedPositions->SetPoint(prevIndex, p);
              }
            }
            else
            {
              this->Prop3Ds->AddItem(static_cast<vtkProp3D *>(prop));

              this->PickedPositions->InsertNextPoint(p);

              // backwards compatibility: also add to this->Actors
              if (actor)
              {
                this->Actors->AddItem(actor);
              }
            }
          }
        }
      }//if visible and pickable and not transparent
    }//for all parts
  }//for all actors

  int picked = 0;

  if (this->Path)
  {
    // Invoke pick method if one defined - prop goes first
    this->Path->GetFirstNode()->GetViewProp()->Pick();
    this->InvokeEvent(vtkCommand::PickEvent,nullptr);
    picked = 1;
  }

  return picked;
}

//----------------------------------------------------------------------
// Intersect data with specified ray.
double vtkPicker::IntersectWithLine(double p1[3], double p2[3],
                                   double tol,
                                   vtkAssemblyPath *path,
                                   vtkProp3D *prop3D,
                                   vtkAbstractMapper3D *mapper)
{
  double center[3], t, ray[3], rayFactor;

  // Get the data from the modeler
  if ( mapper != nullptr )
  {
    mapper->GetCenter(center);
  }
  else
  {
    return VTK_DOUBLE_MAX;
  }

  if ( !vtkPicker::CalculateRay(p1, p2, ray, rayFactor) )
  {
    vtkDebugMacro("Zero length ray");
    return 2.0;
  }

  // Project the center point onto the ray and determine its parametric value
  //
  t = (ray[0]*(center[0]-p1[0]) +
       ray[1]*(center[1]-p1[1]) +
       ray[2]*(center[2]-p1[2])) / rayFactor;

  if ( t >= 0.0 && t <= 1.0 && t < this->GlobalTMin )
  {
    // If this is a composite dataset, find the nearest picked dataset
    vtkCompositeDataSet* composite =
        vtkCompositeDataSet::SafeDownCast(mapper->GetInputDataObject(0,0));
    if ( composite )
    {
      double tMinDS = VTK_DOUBLE_MAX;
      double centerMinDS[3];
      vtkDataSet* minDS = nullptr;
      vtkIdType minDSIndex =-1;
      vtkSmartPointer<vtkCompositeDataIterator> iter;
      iter.TakeReference( composite->NewIterator() );
      for (iter->InitTraversal();
           !iter->IsDoneWithTraversal();
           iter->GoToNextItem())
      {
        vtkDataSet* ds =
            vtkDataSet::SafeDownCast(iter->GetCurrentDataObject());
        if ( !ds )
        {
          continue;
        }

        // First check if the bounding box of the data set is hit.
        double bounds[6];
        ds->GetBounds(bounds);
        bounds[0] -= tol; bounds[1] += tol;
        bounds[2] -= tol; bounds[3] += tol;
        bounds[4] -= tol; bounds[5] += tol;
        double tDummy;
        double xyzDummy[3];
        if ( !vtkBox::IntersectBox(bounds, p1, ray, xyzDummy, tDummy) )
        {
          // box not hit: no need to intersect...
          continue;
        }

        double centerDS[3];
        ds->GetCenter( centerDS );

        // Project the center point onto the ray and
        // determine its parametric value
        double tDS = (ray[0]*(centerDS[0]-p1[0]) +
                      ray[1]*(centerDS[1]-p1[1]) +
                      ray[2]*(centerDS[2]-p1[2])) / rayFactor;

        if ( tDS >= 0.0 && tDS <= 1.0 && tDS < tMinDS )
        {
          tMinDS = tDS;
          centerMinDS[0] = centerDS[0];
          centerMinDS[1] = centerDS[1];
          centerMinDS[2] = centerDS[2];
          minDS = ds;
          minDSIndex = iter->GetCurrentFlatIndex();
        }
      }
      // Note that the mapper position is not the center of the entire
      // composite data set but the center of the nearest data set
      this->MarkPickedData(path,tMinDS,centerMinDS,mapper,minDS,minDSIndex);
    }
    else
    {
      this->MarkPicked(path, prop3D, mapper, t, center);
    }
  }
  return t;
}

bool vtkPicker::CalculateRay(double p1[3], double p2[3],
                             double ray[3], double &rayFactor)
{
  ray[0] = p2[0] - p1[0];
  ray[1] = p2[1] - p1[1];
  ray[2] = p2[2] - p1[2];

  rayFactor = vtkMath::Dot(ray,ray);
  return ( rayFactor > 0.0 );
}

//----------------------------------------------------------------------
// Initialize the picking process.
void vtkPicker::Initialize()
{
  this->vtkAbstractPropPicker::Initialize();

  this->Actors->RemoveAllItems();
  this->Prop3Ds->RemoveAllItems();
  this->PickedPositions->Reset();

  this->MapperPosition[0] = 0.0;
  this->MapperPosition[1] = 0.0;
  this->MapperPosition[2] = 0.0;

  this->Mapper = nullptr;
  this->DataSet = nullptr;
  this->CompositeDataSet = nullptr;
  this->FlatBlockIndex = -1;
  this->GlobalTMin = VTK_DOUBLE_MAX;
}


//----------------------------------------------------------------------
vtkActorCollection *vtkPicker::GetActors()
{
  if (this->Actors->GetNumberOfItems() !=
        this->PickedPositions->GetNumberOfPoints())
  {
    vtkWarningMacro(<<"Not all Prop3Ds are actors, use GetProp3Ds instead");
  }
  return this->Actors;
}


//----------------------------------------------------------------------
void vtkPicker::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  if ( this->DataSet )
  {
    os << indent << "DataSet: " << this->DataSet << "\n";
  }
  else
  {
    os << indent << "DataSet: (none)";
  }
  if ( this->CompositeDataSet )
  {
    os << indent << "CompositeDataSet: "<<this->CompositeDataSet<<"\n";
  }
  else
  {
    os << indent << "CompositeDataSet: (none)\n";
  }
  if ( this->FlatBlockIndex > -1 )
  {
    os << indent << "FlatBlockIndex: "<<this->FlatBlockIndex<<"\n";
  }
  else
  {
    os << indent << "FlatBlockIndex: (none)\n";
  }

  os << indent << "Mapper: " << this->Mapper << "\n";

  os << indent << "Tolerance: " << this->Tolerance << "\n";

  os << indent << "MapperPosition: (" <<  this->MapperPosition[0] << ","
     << this->MapperPosition[1] << ","
     << this->MapperPosition[2] << ")\n";
}