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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkOBBTree.h,v $
  Language:  C++
  Date:      $Date: 2001/10/11 13:37:10 $
  Version:   $Revision: 1.37 $
  Thanks:    Thanks to Peter C. Everett <pce@world.std.com> for
             improvements and enhancements to vtkOBBTree class.


Copyright (c) 1993-2001 Ken Martin, Will Schroeder, Bill Lorensen 
All rights reserved.

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 * Neither name of Ken Martin, Will Schroeder, or Bill Lorensen nor the names
   of any contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

 * Modified source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

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=========================================================================*/
// .NAME vtkOBBTree - generate oriented bounding box (OBB) tree
// .SECTION Description
// vtkOBBTree is an object to generate oriented bounding box (OBB) trees.
// An oriented bounding box is a bounding box that does not necessarily line 
// up along coordinate axes. The OBB tree is a hierarchical tree structure 
// of such boxes, where deeper levels of OBB confine smaller regions of space.
//
// To build the OBB, a recursive, top-down process is used. First, the root OBB
// is constructed by finding the mean and covariance matrix of the cells (and
// their points) that define the dataset. The eigenvectors of the covariance
// matrix are extracted, giving a set of three orthogonal vectors that define 
// the tightest-fitting OBB. To create the two children OBB's, a split plane 
// is found that (approximately) divides the number cells in half. These are 
// then assigned to the children OBB's. This process then continues until
// the MaxLevel ivar limits the recursion, or no split plane can be found.
//
// A good reference for OBB-trees is Gottschalk & Manocha in Proceedings of 
// Siggraph `96.

// .SECTION Caveats
// Since this algorithms works from a list of cells, the OBB tree will only 
// bound the "geometry" attached to the cells if the convex hull of the 
// cells bounds the geometry.
//
// Long, skinny cells (i.e., cells with poor aspect ratio) may cause 
// unsatisfactory results. This is due to the fact that this is a top-down
// implementation of the OBB tree, requiring that one or more complete cells
// are contained in each OBB. This requirement makes it hard to find good 
// split planes during the recursion process. A bottom-up implementation would
// go a long way to correcting this problem.

// .SECTION See Also
// vtkLocator vtkCellLocator vtkLocatorFilter

#ifndef __vtkOBBTree_h
#define __vtkOBBTree_h

#include "vtkCellLocator.h"
#include "vtkMatrix4x4.h"

// Special class defines node for the OBB tree
//
//BTX
//
class vtkOBBNode { //;prevent man page generation
public:
  vtkOBBNode();
  ~vtkOBBNode();

  float Corner[3]; //center point of this node
  float Axes[3][3]; //the axes defining the OBB - ordered from long->short
  vtkOBBNode *Parent; //parent node; NULL if root
  vtkOBBNode **Kids; //two children of this node; NULL if leaf
  vtkIdList *Cells; //list of cells in node
  void DebugPrintTree( int level, double *leaf_vol, int *minCells,
                       int *maxCells );
};
//ETX
//

class VTK_GRAPHICS_EXPORT vtkOBBTree : public vtkCellLocator
{
public:
  vtkTypeMacro(vtkOBBTree,vtkCellLocator);

  // Description:
  // Construct with automatic computation of divisions, averaging
  // 25 cells per octant.
  static vtkOBBTree *New();

  // Description:
  // Compute an OBB from the list of points given. Return the corner point
  // and the three axes defining the orientation of the OBB. Also return
  // a sorted list of relative "sizes" of axes for comparison purposes.
  void ComputeOBB(vtkPoints *pts, float corner[3], float max[3], 
                  float mid[3], float min[3], float size[3]);

  // Description:
  // Compute an OBB for the input dataset using the cells in the data.
  // Return the corner point and the three axes defining the orientation
  // of the OBB. Also return a sorted list of relative "sizes" of axes for
  // comparison purposes.
  void ComputeOBB(vtkDataSet *input, float corner[3], float max[3],
                  float mid[3], float min[3], float size[3]);

  // Description:
  // Determine whether a point is inside or outside the data used to build
  // this OBB tree.  The data must be a closed surface vtkPolyData data set.
  // The return value is +1 if outside, -1 if inside, and 0 if undecided.
  int InsideOrOutside(const float point[3]);

  // Description:
  // Take the passed line segment and intersect it with the data set.
  // This method assumes that the data set is a vtkPolyData that describes
  // a closed surface, and the intersection points that are returned in
  // 'points' alternate between entrance points and exit points.
  // The return value of the function is 0 if no intersections were found,
  // -1 if point 'a0' lies inside the closed surface, or +1 if point 'a0'
  // lies outside the closed surface.
  // Either 'points' or 'cellIds' can be set to NULL if you don't want
  // to receive that information.
  int IntersectWithLine(const float a0[3], const float a1[3],
                        vtkPoints *points, vtkIdList *cellIds);

  // Description:
  // Return the first intersection of the specified line segment with
  // the OBB tree, as well as information about the cell which the
  // line segment intersected.
  int IntersectWithLine(float a0[3], float a1[3], float tol,
                        float& t, float x[3], float pcoords[3],
                        int &subId);

  int IntersectWithLine(float a0[3], float a1[3], float tol,
                        float& t, float x[3], float pcoords[3],
                        int &subId, vtkIdType &cellId);
  
  int IntersectWithLine(float a0[3], float a1[3], float tol,
                        float& t, float x[3], float pcoords[3],
                        int &subId, vtkIdType &cellId, vtkGenericCell *cell);

  //BTX

  // Description:
  // Returns true if nodeB and nodeA are disjoint after optional
  // transformation of nodeB with matrix XformBtoA
  int DisjointOBBNodes( vtkOBBNode *nodeA, vtkOBBNode *nodeB,
                        vtkMatrix4x4 *XformBtoA );

  // Description:
  // Returns true if line intersects node.
  int LineIntersectsNode( vtkOBBNode *pA, float B0[3], float B1[3] );

  // Description:
  // Returns true if triangle (optionally transformed) intersects node.
  int TriangleIntersectsNode( vtkOBBNode *pA,
                              float p0[3], float p1[3],
                              float p2[3], vtkMatrix4x4 *XformBtoA );

  // Description:
  // For each intersecting leaf node pair, call function.
  // OBBTreeB is optionally transformed by XformBtoA before testing.
  int IntersectWithOBBTree( vtkOBBTree *OBBTreeB, vtkMatrix4x4 *XformBtoA,
                            int(*function)( vtkOBBNode *nodeA,
                                            vtkOBBNode *nodeB,
                                            vtkMatrix4x4 *Xform,
                                            void *arg ),
                            void *data_arg );
  //ETX

  // Description:
  // Satisfy locator's abstract interface, see vtkLocator.
  void FreeSearchStructure();
  void BuildLocator();

  // Description:
  // Create polygonal representation for OBB tree at specified level. If
  // level < 0, then the leaf OBB nodes will be gathered. The aspect ratio (ar)
  // and line diameter (d) are used to control the building of the
  // representation. If a OBB node edge ratio's are greater than ar, then the
  // dimension of the OBB is collapsed (OBB->plane->line). A "line" OBB will be
  // represented either as two crossed polygons, or as a line, depending on
  // the relative diameter of the OBB compared to the diameter (d).
  void GenerateRepresentation(int level, vtkPolyData *pd);

  //BTX
protected:
  vtkOBBTree();
  ~vtkOBBTree();

  // Compute an OBB from the list of cells given.  This used to be
  // public but should not have been.  A public call has been added
  // so that the functionality can be accessed.
  void ComputeOBB(vtkIdList *cells, float corner[3], float max[3], 
                       float mid[3], float min[3], float size[3]);

  vtkOBBNode *Tree;
  void BuildTree(vtkIdList *cells, vtkOBBNode *parent, int level);
  vtkPoints *PointsList;
  int *InsertedPoints;
  int OBBCount;
  int DeepestLevel;

  void DeleteTree(vtkOBBNode *OBBptr);
  void GeneratePolygons(vtkOBBNode *OBBptr, int level, int repLevel, 
                        vtkPoints* pts, vtkCellArray *polys);

  //ETX
private:
  vtkOBBTree(const vtkOBBTree&);  // Not implemented.
  void operator=(const vtkOBBTree&);  // Not implemented.
};

#endif
