Method IntersectVolumeWithLine

Rendering/Volume/vtkVolumePicker.cxx:48–211

// same method in the superclass, this method will look for cropping planes.

double vtkVolumePicker::IntersectVolumeWithLine(const double p1[3], const double p2[3], double t1,
  double t2, vtkProp3D* prop, vtkAbstractVolumeMapper* mapper)
{
  double tMin = VTK_DOUBLE_MAX;

  vtkImageData* data = vtkImageData::SafeDownCast(mapper->GetDataSetInput());
  vtkVolumeMapper* vmapper = vtkVolumeMapper::SafeDownCast(mapper);

  if (data == nullptr)
  {
    // This picker only works with image inputs
    return VTK_DOUBLE_MAX;
  }

  // Convert ray to structured coordinates
  double spacing[3], origin[3];
  int extent[6];
  data->GetSpacing(spacing);
  data->GetOrigin(origin);
  data->GetExtent(extent);

  double x1[3], x2[3];
  for (int i = 0; i < 3; i++)
  {
    x1[i] = (p1[i] - origin[i]) / spacing[i];
    x2[i] = (p2[i] - origin[i]) / spacing[i];
  }

  // These are set to the plane that the ray enters through
  int planeId = -1;
  int extentPlaneId = -1;

  // There might be multiple regions, depending on cropping flags
  int numSegments = 1;
  double t1List[16], t2List[16], s1List[16];
  int planeIdList[16];
  t1List[0] = t1;
  t2List[0] = t2;
  // s1 is the cropping plane intersection, initialize to large value
  double s1 = s1List[0] = VTK_DOUBLE_MAX;
  planeIdList[0] = -1;

  // Find the cropping bounds in structured coordinates
  double bounds[6];
  for (int j = 0; j < 6; j++)
  {
    bounds[j] = extent[j];
  }

  if (vmapper && vmapper->GetCropping())
  {
    vmapper->GetCroppingRegionPlanes(bounds);
    for (int j = 0; j < 3; j++)
    {
      double b1 = (bounds[2 * j] - origin[j]) / spacing[j];
      double b2 = (bounds[2 * j + 1] - origin[j]) / spacing[j];
      bounds[2 * j] = (b1 < b2 ? b1 : b2);
      bounds[2 * j + 1] = (b1 < b2 ? b2 : b1);