Method IsCameraInside

Rendering/VolumeOpenGL2/vtkOpenGLGPUVolumeRayCastMapper.cxx:1015–1067

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//------------------------------------------------------------------------------
bool vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::IsCameraInside(
  vtkRenderer* ren, vtkVolume* vol, double geometry[24])
{
  vtkNew<vtkMatrix4x4> dataToWorld;
  vol->GetModelToWorldMatrix(dataToWorld);

  vtkCamera* cam = ren->GetActiveCamera();

  double planes[24];
  cam->GetFrustumPlanes(ren->GetTiledAspectRatio(), planes);

  // convert geometry to world then compare to frustum planes
  double in[4];
  in[3] = 1.0;
  double out[4];
  double worldGeometry[24];
  for (int i = 0; i < 8; ++i)
  {
    in[0] = geometry[i * 3];
    in[1] = geometry[i * 3 + 1];
    in[2] = geometry[i * 3 + 2];
    dataToWorld->MultiplyPoint(in, out);
    worldGeometry[i * 3] = out[0] / out[3];
    worldGeometry[i * 3 + 1] = out[1] / out[3];
    worldGeometry[i * 3 + 2] = out[2] / out[3];
  }

  // does the front clipping plane intersect the volume?
  // true if points are on both sides of the plane
  bool hasPositive = false;
  bool hasNegative = false;
  bool hasZero = false;
  for (int i = 0; i < 8; ++i)
  {
    double val = planes[4 * 4] * worldGeometry[i * 3] +
      planes[4 * 4 + 1] * worldGeometry[i * 3 + 1] + planes[4 * 4 + 2] * worldGeometry[i * 3 + 2] +
      planes[4 * 4 + 3];
    if (val < 0)
    {
      hasNegative = true;
    }
    else if (val > 0)
    {
      hasPositive = true;
    }
    else
    {
      hasZero = true;
    }
  }

  return hasZero || (hasNegative && hasPositive);
}

//------------------------------------------------------------------------------
bool vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::IsGeometryUpdateRequired(