vtkUnstructuredGridBunykRayCastFunction.h

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

  Program:   Visualization Toolkit
  Module:    vtkUnstructuredGridBunykRayCastFunction.h

  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.

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

#ifndef vtkUnstructuredGridBunykRayCastFunction_h
#define vtkUnstructuredGridBunykRayCastFunction_h

#include "vtkRenderingVolumeModule.h" // For export macro
#include "vtkUnstructuredGridVolumeRayCastFunction.h"

class vtkRenderer;
class vtkVolume;
class vtkUnstructuredGridVolumeRayCastMapper;
class vtkMatrix4x4;
class vtkPiecewiseFunction;
class vtkColorTransferFunction;
class vtkUnstructuredGridBase;
class vtkIdList;
class vtkDoubleArray;
class vtkDataArray;

// We manage the memory for the list of intersections ourself - this is the
// storage used. We keep 10,000 elements in each array, and we can have up to
// 1,000 arrays.
#define VTK_BUNYKRCF_MAX_ARRAYS 10000
#define VTK_BUNYKRCF_ARRAY_SIZE 10000

class VTKRENDERINGVOLUME_EXPORT vtkUnstructuredGridBunykRayCastFunction : public vtkUnstructuredGridVolumeRayCastFunction
{
public:
  static vtkUnstructuredGridBunykRayCastFunction *New();
  vtkTypeMacro(vtkUnstructuredGridBunykRayCastFunction,vtkUnstructuredGridVolumeRayCastFunction);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  void Initialize( vtkRenderer *ren, vtkVolume   *vol ) override;

  void Finalize() override;

  VTK_NEWINSTANCE
  vtkUnstructuredGridVolumeRayCastIterator *NewIterator() override;

  // Used to store each triangle - made public because of the
  // templated function
  class Triangle {
  public:
    vtkIdType PointIndex[3];
    vtkIdType ReferredByTetra[2];
    double    P1X, P1Y;
    double    P2X, P2Y;
    double    Denominator;
    double    A, B, C, D;
    Triangle *Next;
  };

  // Used to store each intersection for the pixel rays - made
  // public because of the templated function
  class Intersection {
  public:
    Triangle     *TriPtr;
    double        Z;
    Intersection *Next;
  };

  int  InTriangle( double x, double y,
                   Triangle *triPtr );


  double *GetPoints() {return this->Points;}


  vtkGetObjectMacro( ViewToWorldMatrix, vtkMatrix4x4 );


  vtkGetVectorMacro( ImageOrigin, int, 2 );


  vtkGetVectorMacro( ImageViewportSize, int, 2 );

  Triangle **GetTetraTriangles () {return this->TetraTriangles;}

  Intersection *GetIntersectionList( int x, int y ) { return this->Image[y*this->ImageSize[0] + x]; }

protected:
  vtkUnstructuredGridBunykRayCastFunction();
  ~vtkUnstructuredGridBunykRayCastFunction() override;

  // These are cached during the initialize method so that they do not
  // need to be passed into subsequent CastRay calls.
  vtkRenderer                             *Renderer;
  vtkVolume                               *Volume;
  vtkUnstructuredGridVolumeRayCastMapper  *Mapper;

  // Computed during the initialize method - if something is
  // wrong (no mapper, no volume, no input, etc.) then no rendering
  // will actually be performed.
  int                                      Valid;

  // These are the transformed points
  int      NumberOfPoints;
  double  *Points;

  // This is the matrix that will take a transformed point back
  // to world coordinates
  vtkMatrix4x4 *ViewToWorldMatrix;


  // This is the intersection list per pixel in the image
  Intersection    **Image;

  // This is the size of the image we are computing (which does
  // not need to match the screen size)
  int               ImageSize[2];

  // Since we may only be computing a subregion of the "full" image,
  // this is the origin of the region we are computing. We must
  // subtract this origin from any pixel (x,y) locations before
  // accessing the pixel in this->Image (which represents only the
  // subregion)
  int               ImageOrigin[2];

  // This is the full size of the image
  int               ImageViewportSize[2];

  // These are values saved for the building of the TriangleList. Basically
  // we need to check if the data has changed in some way.
  vtkUnstructuredGridBase   *SavedTriangleListInput;
  vtkTimeStamp               SavedTriangleListMTime;

  // This is a memory intensive algorithm! For each tetra in the
  // input data we create up to 4 triangles (we don't create duplicates)
  // This is the TriangleList. Then, for each tetra we keep track of
  // the pointer to each of its four triangles - this is the
  // TetraTriangles. We also keep a duplicate list of points
  // (transformed into view space) - these are the Points.
  Triangle **TetraTriangles;
  vtkIdType TetraTrianglesSize;

  Triangle  *TriangleList;

  // Compute whether a boundary triangle is front facing by
  // looking at the fourth point in the tetra to see if it is
  // in front (triangle is backfacing) or behind (triangle is
  // front facing) the plane containing the triangle.
  int  IsTriangleFrontFacing( Triangle *triPtr, vtkIdType tetraIndex );

  // The image contains lists of intersections per pixel - we
  // need to clear this during the initialization phase for each
  // render.
  void ClearImage();

  // This is the memory buffer used to build the intersection
  // lists. We do our own memory management here because allocating
  // a bunch of small elements during rendering is too slow.
  Intersection *IntersectionBuffer[VTK_BUNYKRCF_MAX_ARRAYS];
  int           IntersectionBufferCount[VTK_BUNYKRCF_MAX_ARRAYS];

  // This method replaces new for creating a new element - it
  // returns one from the big block already allocated (it
  // allocates another big block if necessary)
  void         *NewIntersection();

  // This method is used during the initialization process to
  // check the validity of the objects - missing information
  // such as the volume, renderer, mapper, etc. will be flagged
  // and reported.
  int          CheckValidity(vtkRenderer *ren,
                             vtkVolume   *vol);

  // This method is used during the initialization process to
  // transform the points to view coordinates
  void          TransformPoints();

  // This method is used during the initialization process to
  // create the list of triangles if the data has changed
  void          UpdateTriangleList();

  // This method is used during the initialization process to
  // update the view dependent information in the triangle list
  void          ComputeViewDependentInfo();

  // This method is used during the initialization process to
  // compute the intersections for each pixel with the boundary
  // triangles.
  void          ComputePixelIntersections();

private:
  vtkUnstructuredGridBunykRayCastFunction(const vtkUnstructuredGridBunykRayCastFunction&) = delete;
  void operator=(const vtkUnstructuredGridBunykRayCastFunction&) = delete;
};

#endif