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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkCamera.cxx,v $

  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 "vtkCamera.h"

#include "vtkMath.h"
#include "vtkTimeStamp.h"
#include "vtkGraphicsFactory.h"
#include "vtkPerspectiveTransform.h"
#include "vtkTransform.h"

#include <math.h>

vtkCxxRevisionMacro(vtkCamera, "$Revision: 1.109 $");

//----------------------------------------------------------------------------
// Needed when we don't use the vtkStandardNewMacro.
vtkInstantiatorNewMacro(vtkCamera);

//----------------------------------------------------------------------------
// Construct camera instance with its focal point at the origin, 
// and position=(0,0,1). The view up is along the y-axis, 
// view angle is 30 degrees, and the clipping range is (.1,1000).
vtkCamera::vtkCamera()
{
  this->FocalPoint[0] = 0.0;
  this->FocalPoint[1] = 0.0;
  this->FocalPoint[2] = 0.0;

  this->Position[0] = 0.0;
  this->Position[1] = 0.0;
  this->Position[2] = 1.0;

  this->ViewUp[0] = 0.0;
  this->ViewUp[1] = 1.0;
  this->ViewUp[2] = 0.0;

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

  this->ViewAngle = 30.0;
  this->UseHorizontalViewAngle = 0;

  this->ClippingRange[0] = 0.01;
  this->ClippingRange[1] = 1000.01;
  this->Thickness = 1000.0;

  this->ParallelProjection = 0;
  this->ParallelScale = 1.0;
 
  this->EyeAngle = 2.0;
  this->Stereo = 0;
  this->LeftEye = 1;

  this->WindowCenter[0] = 0.0;
  this->WindowCenter[1] = 0.0;
  
  this->ViewShear[0] = 0.0;
  this->ViewShear[1] = 0.0;
  this->ViewShear[2] = 1.0;

  this->FocalDisk = 1.0;

  this->Transform = vtkPerspectiveTransform::New();
  this->ViewTransform = vtkTransform::New();
  this->PerspectiveTransform = vtkPerspectiveTransform::New();
  this->CameraLightTransform = vtkTransform::New();
  this->UserTransform = NULL;

  // initialize the ViewTransform
  this->ComputeViewTransform();
  this->ComputeDistance();
  this->ComputeCameraLightTransform();
}

//----------------------------------------------------------------------------
vtkCamera::~vtkCamera()
{
  this->Transform->Delete();
  this->ViewTransform->Delete();
  this->PerspectiveTransform->Delete();
  this->CameraLightTransform->Delete();
  if (this->UserTransform)
    {
    this->UserTransform->UnRegister(this);
    this->UserTransform = NULL;
    }
}

//----------------------------------------------------------------------------
// return the correct type of Camera 
vtkCamera *vtkCamera::New()
{
  // First try to create the object from the vtkObjectFactory
  vtkObject* ret = vtkGraphicsFactory::CreateInstance("vtkCamera");
  return (vtkCamera*)ret;
}

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
// The first set of methods deal exclusively with the ViewTransform, which
// is the only transform which is set up entirely in the camera.  The
// perspective transform must be set up by the Renderer because the 
// Camera doesn't know the Renderer's aspect ratio.
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

//----------------------------------------------------------------------------
void vtkCamera::SetPosition(double x, double y, double z)
{
  if (x == this->Position[0] && 
      y == this->Position[1] &&
      z == this->Position[2])
    {
    return;
    }
  
  this->Position[0] = x;
  this->Position[1] = y;
  this->Position[2] = z;

  vtkDebugMacro(<< " Position set to ( " <<  this->Position[0] << ", " 
                << this->Position[1] << ", " << this->Position[2] << ")");

  this->ComputeViewTransform();
  // recompute the focal distance
  this->ComputeDistance();
  this->ComputeCameraLightTransform();

  this->Modified();
}

void vtkCamera::SetUserTransform(vtkHomogeneousTransform *transform)
{
  if (transform == this->UserTransform) 
    { 
    return; 
    }
  if (this->UserTransform) 
    {
    this->UserTransform->Delete();
    this->UserTransform = NULL;
    }
  if (transform)
    {
    this->UserTransform = transform;
    this->UserTransform->Register(this);
    }
  this->Modified();
}

//----------------------------------------------------------------------------
void vtkCamera::SetFocalPoint(double x, double y, double z)
{
  if (x == this->FocalPoint[0] && 
      y == this->FocalPoint[1] && 
      z == this->FocalPoint[2])
    {
    return;
    }

  this->FocalPoint[0] = x; 
  this->FocalPoint[1] = y; 
  this->FocalPoint[2] = z;

  vtkDebugMacro(<< " FocalPoint set to ( " <<  this->FocalPoint[0] << ", " << this->FocalPoint[1] << ", " << this->FocalPoint[2] << ")");

  this->ComputeViewTransform();
  // recompute the focal distance
  this->ComputeDistance();
  this->ComputeCameraLightTransform();

  this->Modified();
}

//----------------------------------------------------------------------------
void vtkCamera::SetViewUp(double x, double y, double z)
{
  // normalize ViewUp, but do _not_ orthogonalize it by default
  double norm = sqrt(x*x + y*y + z*z);
  
  if(norm != 0) 
    {
    x /= norm; 
    y /= norm; 
    z /= norm;
    }
  else 
    {
    x = 0; 
    y = 1; 
    z = 0;
    }
  
  if (x == this->ViewUp[0] && 
      y == this->ViewUp[1] &&
      z == this->ViewUp[2])
    {
    return;
    }

  this->ViewUp[0] = x;
  this->ViewUp[1] = y;
  this->ViewUp[2] = z;

  vtkDebugMacro(<< " ViewUp set to ( " <<  this->ViewUp[0] << ", " << this->ViewUp[1] << ", " << this->ViewUp[2] << ")");
  
  this->ComputeViewTransform();
  this->ComputeCameraLightTransform();
  this->Modified();
}

//----------------------------------------------------------------------------
// The ViewTransform depends on only three ivars:  the Position, the
// FocalPoint, and the ViewUp vector.  All the other methods are there
// simply for the sake of the users' convenience.
void vtkCamera::ComputeViewTransform()
{
  // main view through the camera
  this->Transform->Identity();
  this->Transform->SetupCamera(this->Position, this->FocalPoint, this->ViewUp);
  this->ViewTransform->SetMatrix(this->Transform->GetMatrix());
}

//----------------------------------------------------------------------------
void vtkCamera::ComputeCameraLightTransform()
{
  vtkTransform *t;
  double d;

  // assumes a valid view transform and valid camera distance

  t = this->CameraLightTransform;
  t->Identity();
  t->SetMatrix(this->ViewTransform->GetMatrix());
  t->Inverse();

  d = this->Distance;
  t->Scale(d, d, d);
  t->Translate(0.0, 0.0, -1.0);
}

//----------------------------------------------------------------------------
void vtkCamera::OrthogonalizeViewUp()
{
  // the orthogonalized ViewUp is just the second row of the view matrix
  vtkMatrix4x4 *matrix = this->ViewTransform->GetMatrix();
  this->ViewUp[0] = matrix->GetElement(1,0);
  this->ViewUp[1] = matrix->GetElement(1,1);
  this->ViewUp[2] = matrix->GetElement(1,2);

  this->Modified();
}

//----------------------------------------------------------------------------
// Set the distance of the focal point from the camera. The focal point is 
// modified accordingly. This should be positive.
void vtkCamera::SetDistance(double d)
{
  if (this->Distance == d)
    {
    return;
    }

  this->Distance = d; 

  // Distance should be greater than .0002
  if (this->Distance < 0.0002) 
    {
    this->Distance = 0.0002;
    vtkDebugMacro(<< " Distance is set to minimum.");
    }
  
  // we want to keep the camera pointing in the same direction
  double *vec = this->DirectionOfProjection;

  // recalculate FocalPoint
  this->FocalPoint[0] = this->Position[0] + vec[0]*this->Distance;
  this->FocalPoint[1] = this->Position[1] + vec[1]*this->Distance;
  this->FocalPoint[2] = this->Position[2] + vec[2]*this->Distance;

  vtkDebugMacro(<< " Distance set to ( " <<  this->Distance << ")");

  this->ComputeViewTransform();
  this->ComputeCameraLightTransform();
  this->Modified();
}  

//----------------------------------------------------------------------------
// This method must be called when the focal point or camera position changes
void vtkCamera::ComputeDistance()
{
  double dx = this->FocalPoint[0] - this->Position[0];
  double dy = this->FocalPoint[1] - this->Position[1];
  double dz = this->FocalPoint[2] - this->Position[2];

  this->Distance = sqrt(dx*dx + dy*dy + dz*dz);

  if (this->Distance < 0.0002) 
    {
    this->Distance = 0.0002;
    vtkDebugMacro(<< " Distance is set to minimum.");

    double *vec = this->DirectionOfProjection;

    // recalculate FocalPoint
    this->FocalPoint[0] = this->Position[0] + vec[0]*this->Distance;
    this->FocalPoint[1] = this->Position[1] + vec[1]*this->Distance;
    this->FocalPoint[2] = this->Position[2] + vec[2]*this->Distance;
    }

  this->DirectionOfProjection[0] = dx/this->Distance;
  this->DirectionOfProjection[1] = dy/this->Distance;
  this->DirectionOfProjection[2] = dz/this->Distance;

  this->ComputeViewPlaneNormal();
} 

//----------------------------------------------------------------------------
// Move the position of the camera along the view plane normal. Moving
// towards the focal point (e.g., > 1) is a dolly-in, moving away 
// from the focal point (e.g., < 1) is a dolly-out.
void vtkCamera::Dolly(double amount)
{
  if (amount <= 0.0)
    {
    return;
    }
  
  // dolly moves the camera towards the focus
  double d = this->Distance/amount;
  
  this->SetPosition(this->FocalPoint[0] - d*this->DirectionOfProjection[0],
                    this->FocalPoint[1] - d*this->DirectionOfProjection[1],
                    this->FocalPoint[2] - d*this->DirectionOfProjection[2]);
}

//----------------------------------------------------------------------------
// Set the roll angle of the camera about the direction of projection
void vtkCamera::SetRoll(double roll)
{
  // roll is a rotation of camera view up about the direction of projection
  vtkDebugMacro(<< " Setting Roll to " << roll << "");

  // subtract the current roll
  roll -= this->GetRoll();

  if (fabs(roll) < 0.00001)
    {
    return;
    }

  this->Roll(roll);
}

//----------------------------------------------------------------------------
// Returns the roll of the camera.
double vtkCamera::GetRoll()
{
  double orientation[3];
  this->ViewTransform->GetOrientation(orientation);
  return orientation[2];
}

//----------------------------------------------------------------------------
// Rotate the camera around the view plane normal.
void vtkCamera::Roll(double angle)
{
  double newViewUp[3];
  this->Transform->Identity();

  // rotate ViewUp about the Direction of Projection
  this->Transform->RotateWXYZ(angle,this->DirectionOfProjection);

  // okay, okay, TransformPoint shouldn't be used on vectors -- but
  // the transform is rotation with no translation so this works fine.
  this->Transform->TransformPoint(this->ViewUp,newViewUp);
  this->SetViewUp(newViewUp);
}

//----------------------------------------------------------------------------
// Rotate the focal point about the view up vector centered at the camera's 
// position. 
void vtkCamera::Yaw(double angle)
{
  double newFocalPoint[3];
  double *pos = this->Position;
  this->Transform->Identity();

  // translate the camera to the origin,
  // rotate about axis,
  // translate back again
  this->Transform->Translate(+pos[0],+pos[1],+pos[2]);   
  this->Transform->RotateWXYZ(angle,this->ViewUp);
  this->Transform->Translate(-pos[0],-pos[1],-pos[2]);
  
  // now transform focal point
  this->Transform->TransformPoint(this->FocalPoint,newFocalPoint);
  this->SetFocalPoint(newFocalPoint);
}

//----------------------------------------------------------------------------
// Rotate the focal point about the cross product of the view up vector 
// and the negative of the , centered at the camera's position.
void vtkCamera::Pitch(double angle)
{
  double axis[3], newFocalPoint[3];
  double *pos = this->Position;
  this->Transform->Identity();

  // the axis is the first row of the view transform matrix
  axis[0] = this->ViewTransform->GetMatrix()->GetElement(0,0);
  axis[1] = this->ViewTransform->GetMatrix()->GetElement(0,1);
  axis[2] = this->ViewTransform->GetMatrix()->GetElement(0,2);
  
  // translate the camera to the origin,
  // rotate about axis,
  // translate back again
  this->Transform->Translate(+pos[0],+pos[1],+pos[2]);   
  this->Transform->RotateWXYZ(angle,axis);
  this->Transform->Translate(-pos[0],-pos[1],-pos[2]);
  
  // now transform focal point
  this->Transform->TransformPoint(this->FocalPoint,newFocalPoint);
  this->SetFocalPoint(newFocalPoint);
}

//----------------------------------------------------------------------------
// Rotate the camera about the view up vector centered at the focal point.
void vtkCamera::Azimuth(double angle)
{
  double newPosition[3];
  double *fp = this->FocalPoint;
  this->Transform->Identity();

  // translate the focal point to the origin,
  // rotate about view up,
  // translate back again  
  this->Transform->Translate(+fp[0],+fp[1],+fp[2]);   
  this->Transform->RotateWXYZ(angle,this->ViewUp);
  this->Transform->Translate(-fp[0],-fp[1],-fp[2]);
  
  // apply the transform to the position
  this->Transform->TransformPoint(this->Position,newPosition);
  this->SetPosition(newPosition);
}

//----------------------------------------------------------------------------
// Rotate the camera about the cross product of the negative of the
// direction of projection and the view up vector centered on the focal point.
void vtkCamera::Elevation(double angle)
{
  double axis[3], newPosition[3];
  double *fp = this->FocalPoint;
  this->Transform->Identity();

  // snatch the axis from the view transform matrix
  axis[0] = -this->ViewTransform->GetMatrix()->GetElement(0,0);
  axis[1] = -this->ViewTransform->GetMatrix()->GetElement(0,1);
  axis[2] = -this->ViewTransform->GetMatrix()->GetElement(0,2);
  
  // translate the focal point to the origin,
  // rotate about axis,
  // translate back again
  this->Transform->Translate(+fp[0],+fp[1],+fp[2]);   
  this->Transform->RotateWXYZ(angle,axis);
  this->Transform->Translate(-fp[0],-fp[1],-fp[2]);
  
  // now transform position
  this->Transform->TransformPoint(this->Position,newPosition);
  this->SetPosition(newPosition);
}

//----------------------------------------------------------------------------
// Apply Transform to camera
void vtkCamera::ApplyTransform(vtkTransform *t) {
  
  double posOld[4], posNew[4], fpOld[4], fpNew[4], vuOld[4], vuNew[4];

  this->GetPosition(posOld);
  this->GetFocalPoint(fpOld);
  this->GetViewUp(vuOld);

  posOld[3] = 1.0;
  fpOld[3] = 1.0;
  vuOld[3] = 1.0;

  vuOld[0] += posOld[0];
  vuOld[1] += posOld[1];
  vuOld[2] += posOld[2];

  t->MultiplyPoint(posOld, posNew);
  t->MultiplyPoint(fpOld, fpNew);
  t->MultiplyPoint(vuOld, vuNew);

  vuNew[0] -= posNew[0];
  vuNew[1] -= posNew[1];
  vuNew[2] -= posNew[2];

  this->SetPosition(posNew);
  this->SetFocalPoint(fpNew);
  this->SetViewUp(vuNew);
  
} 

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
// The following methods set up the information that the Renderer needs
// to set up the perspective transform.  The transformation matrix is
// created using the GetPerspectiveTransformMatrix method.
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

//----------------------------------------------------------------------------
void vtkCamera::SetParallelProjection(int flag)
{
  if ( this->ParallelProjection != flag ) 
    {
    this->ParallelProjection = flag;
    this->Modified();
    this->ViewingRaysModified(); 
    } 
}

//----------------------------------------------------------------------------
void vtkCamera::SetViewAngle(double angle)
{
  double min =   0.00000001;
  double max = 179.0;

  if ( this->ViewAngle != angle )
    {
    this->ViewAngle = (angle<min?min:(angle>max?max:angle));
    this->Modified();
    this->ViewingRaysModified();
    }
}

//----------------------------------------------------------------------------
void vtkCamera::SetUseHorizontalViewAngle(int flag)
{
  if (flag == this->UseHorizontalViewAngle)
    {
    return;
    }
  this->UseHorizontalViewAngle = flag;
  this->Modified();
  this->ViewingRaysModified();
}

//----------------------------------------------------------------------------
void vtkCamera::SetParallelScale(double scale)
{
  if ( this->ParallelScale != scale )
    {
    this->ParallelScale = scale;
    this->Modified();
    this->ViewingRaysModified();
    }
}

//----------------------------------------------------------------------------
// Change the ViewAngle (for perspective) or the ParallelScale (for parallel)
// so that more or less of a scene occupies the viewport.  A value > 1 is a 
// zoom-in. A value < 1 is a zoom-out.
void vtkCamera::Zoom(double amount)
{
  if (amount <= 0.0)
    {
    return;
    }
  
  if (this->ParallelProjection)
    {
    this->SetParallelScale(this->ParallelScale/amount);
    }
  else
    {
    this->SetViewAngle(this->ViewAngle/amount);
    }
}

//----------------------------------------------------------------------------
void vtkCamera::SetClippingRange(double nearz, double farz)
{
  double thickness;
  
  // check the order
  if ( nearz > farz )
    {
    vtkDebugMacro(<< " Front and back clipping range reversed");
    double temp = nearz;
    nearz = farz;
    farz = temp;
    }
  
  // front should be greater than 0.0001
  if (nearz < 0.0001) 
    {
    farz += 0.0001 - nearz;
    nearz = 0.0001;
    vtkDebugMacro(<< " Front clipping range is set to minimum.");
    }
  
  thickness = farz - nearz;
  
  // thickness should be greater than 0.0001
  if (thickness < 0.0001) 
    {
    thickness = 0.0001;
    vtkDebugMacro(<< " ClippingRange thickness is set to minimum.");
    
    // set back plane
    farz = nearz + thickness;
    }
  
  if (nearz == this->ClippingRange[0] && 
      farz == this->ClippingRange[1] && 
      this->Thickness == thickness)
    {
    return;
    }

  this->ClippingRange[0] = nearz; 
  this->ClippingRange[1] = farz; 
  this->Thickness = thickness;
  
  vtkDebugMacro(<< " ClippingRange set to ( " <<  this->ClippingRange[0] << ", "  << this->ClippingRange[1] << ")");

  this->Modified();
}  

//----------------------------------------------------------------------------
// Set the distance between clipping planes. 
// This method adjusts the back clipping plane to the specified thickness
// behind the front clipping plane 
void vtkCamera::SetThickness(double s)
{
  if (this->Thickness == s)
    {
    return;
    }

  this->Thickness = s; 

  // thickness should be greater than 0.0001
  if (this->Thickness < 0.0001) 
    {
    this->Thickness = 0.0001;
    vtkDebugMacro(<< " ClippingRange thickness is set to minimum.");
    }
  
  // set back plane
  this->ClippingRange[1] = this->ClippingRange[0] + this->Thickness;

  vtkDebugMacro(<< " ClippingRange set to ( " <<  this->ClippingRange[0] << ", " << this->ClippingRange[1] << ")");

  this->Modified();
}  

//----------------------------------------------------------------------------
void vtkCamera::SetWindowCenter(double x, double y)
{
  if (this->WindowCenter[0] != x || this->WindowCenter[1] != y)
    {
    this->Modified();
    this->ViewingRaysModified();
    this->WindowCenter[0] = x;
    this->WindowCenter[1] = y;
    }
}

//----------------------------------------------------------------------------
void vtkCamera::SetObliqueAngles(double alpha, double beta)
{
  alpha *= vtkMath::DoubleDegreesToRadians();
  beta *= vtkMath::DoubleDegreesToRadians();

  double cotbeta = cos(beta) / sin(beta);
  double dxdz = cos(alpha) * cotbeta;
  double dydz = sin(alpha) * cotbeta;

  this->SetViewShear(dxdz, dydz, 1.0);
}

//----------------------------------------------------------------------------
// Set the shear transform of the viewing frustum.  Parameters are
// dx/dz, dy/dz, and center.  center is a factor that describes where
// to shear around. The distance dshear from the camera where
// no shear occurs is given by (dshear = center * FocalDistance).
//
void vtkCamera::SetViewShear(double dxdz, double dydz, double center)
{
  if(dxdz != this->ViewShear[0] || 
     dydz != this->ViewShear[1] ||
     center != this->ViewShear[2])
    {
      this->Modified();
      this->ViewingRaysModified();

      this->ViewShear[0] = dxdz;
      this->ViewShear[1] = dydz;
      this->ViewShear[2] = center;
      
      this->ComputeViewPlaneNormal();
    }
}
//----------------------------------------------------------------------------

void vtkCamera::SetViewShear(double d[3]) 
{
  this->SetViewShear(d[0], d[1], d[2]);
}

//----------------------------------------------------------------------------
// Compute the perspective transform matrix. This is used in converting 
// between view and world coordinates.
void vtkCamera::ComputePerspectiveTransform(double aspect, 
                                            double nearz, double farz)
{
  this->PerspectiveTransform->Identity();

  // apply user defined transform last if there is one 
  if (this->UserTransform)
    {
    this->PerspectiveTransform->Concatenate(this->UserTransform->GetMatrix());
    }

  // adjust Z-buffer range
  this->PerspectiveTransform->AdjustZBuffer(-1, +1, nearz, farz);

  if (this->ParallelProjection)
    {
    // set up a rectangular parallelipiped

    double width = this->ParallelScale*aspect;
    double height = this->ParallelScale;

    double xmin = (this->WindowCenter[0]-1.0)*width;
    double xmax = (this->WindowCenter[0]+1.0)*width;
    double ymin = (this->WindowCenter[1]-1.0)*height;
    double ymax = (this->WindowCenter[1]+1.0)*height;

    this->PerspectiveTransform->Ortho(xmin,xmax,ymin,ymax,
                                      this->ClippingRange[0],
                                      this->ClippingRange[1]);
    }
  else
    {
    // set up a perspective frustum

    double tmp = tan(this->ViewAngle*vtkMath::DoubleDegreesToRadians()/2);
    double width;
    double height;
    if (this->UseHorizontalViewAngle)
      {
      width = this->ClippingRange[0]*tmp;
      height = this->ClippingRange[0]*tmp/aspect;
      }
    else
      {
      width = this->ClippingRange[0]*tmp*aspect;
      height = this->ClippingRange[0]*tmp;
      }

    double xmin = (this->WindowCenter[0]-1.0)*width;
    double xmax = (this->WindowCenter[0]+1.0)*width;
    double ymin = (this->WindowCenter[1]-1.0)*height;
    double ymax = (this->WindowCenter[1]+1.0)*height;

    this->PerspectiveTransform->Frustum(xmin, xmax, ymin, ymax,
                                        this->ClippingRange[0],
                                        this->ClippingRange[1]);
    }

  if (this->Stereo)
    {
    // set up a shear for stereo views
    if (this->LeftEye)
      {
      this->PerspectiveTransform->Stereo(-this->EyeAngle/2,
                                         this->Distance);
      }
    else
      {
      this->PerspectiveTransform->Stereo(+this->EyeAngle/2,
                                         this->Distance);
      }
    }

  if (this->ViewShear[0] != 0.0 || this->ViewShear[1] != 0.0) 
    {
    this->PerspectiveTransform->Shear(this->ViewShear[0],
                                      this->ViewShear[1],
                                      this->ViewShear[2]*this->Distance);
    }
  
}

//----------------------------------------------------------------------------
// Return the perspective transform matrix. See ComputePerspectiveTransform.
vtkMatrix4x4 *vtkCamera::GetPerspectiveTransformMatrix(double aspect,
                                                       double nearz,
                                                       double farz)
{
  this->ComputePerspectiveTransform(aspect, nearz, farz);
  
  // return the transform 
  return this->PerspectiveTransform->GetMatrix();
}

//----------------------------------------------------------------------------
// Return the perspective transform matrix. See ComputePerspectiveTransform.
vtkMatrix4x4 *vtkCamera::GetCompositePerspectiveTransformMatrix(double aspect,
                                                                double nearz,
                                                                double farz)
{
  // turn off stereo, the CompositePerspectiveTransformMatrix is used for
  // picking, not for rendering.
  int stereo = this->Stereo;
  this->Stereo = 0;

  this->Transform->Identity();
  this->Transform->Concatenate(this->GetPerspectiveTransformMatrix(aspect,
                                                                   nearz,
                                                                   farz));
  this->Transform->Concatenate(this->GetViewTransformMatrix());

  this->Stereo = stereo;
  
  // return the transform 
  return this->Transform->GetMatrix();
}

//----------------------------------------------------------------------------
// Return the attached light transform matrix.
vtkMatrix4x4 *vtkCamera::GetCameraLightTransformMatrix()
{
  // return the transform 
  return this->CameraLightTransform->GetMatrix();
}


//----------------------------------------------------------------------------
void vtkCamera::ComputeViewPlaneNormal()
{
  if (this->ViewShear[0] != 0.0 || this->ViewShear[1] != 0.0)
    {
    // set the VPN in camera coordinates
    this->ViewPlaneNormal[0] = this->ViewShear[0];
    this->ViewPlaneNormal[1] = this->ViewShear[1];
    this->ViewPlaneNormal[2] = 1.0;
    // transform the VPN to world coordinates using inverse of view transform
    this->ViewTransform->GetLinearInverse()->TransformNormal(
                                              this->ViewPlaneNormal,
                                              this->ViewPlaneNormal);
    }
  else
    {
    // VPN is -DOP
    this->ViewPlaneNormal[0] = -this->DirectionOfProjection[0];
    this->ViewPlaneNormal[1] = -this->DirectionOfProjection[1];
    this->ViewPlaneNormal[2] = -this->DirectionOfProjection[2];
    }
}

//----------------------------------------------------------------------------
void vtkCamera::SetViewPlaneNormal(double vtkNotUsed(x), 
                                   double vtkNotUsed(y),
                                   double vtkNotUsed(z))
{
  vtkWarningMacro(<< "SetViewPlaneNormal:  This method is deprecated, the view plane normal is calculated automatically.");
}

//----------------------------------------------------------------------------
// Return the 6 planes (Ax + By + Cz + D = 0) that bound
// the view frustum. 
void vtkCamera::GetFrustumPlanes(double aspect, double planes[24])
{
  int i;
  double f, normals[6][4], matrix[4][4];

  // set up the normals
  for (i = 0; i < 6; i++)
    {
    normals[i][0] = 0.0;
    normals[i][1] = 0.0;
    normals[i][2] = 0.0;
    normals[i][3] = 1.0;
    // if i is even set to -1, if odd set to +1 
    normals[i][i/2] = 1 - (i%2)*2;
    }

  // get the composite perspective matrix
  vtkMatrix4x4::DeepCopy(
    *matrix, 
    this->GetCompositePerspectiveTransformMatrix(aspect,-1,+1));
  
  // transpose the matrix for use with normals
  vtkMatrix4x4::Transpose(*matrix,*matrix);
  
  // transform the normals to world coordinates
  for (i = 0; i < 6; i++)
    {
    vtkMatrix4x4::MultiplyPoint(*matrix,normals[i],normals[i]);

    f = 1.0/sqrt(normals[i][0]*normals[i][0] +
                 normals[i][1]*normals[i][1] +
                 normals[i][2]*normals[i][2]);
    
    planes[4*i + 0] = normals[i][0]*f;
    planes[4*i + 1] = normals[i][1]*f;
    planes[4*i + 2] = normals[i][2]*f;
    planes[4*i + 3] = normals[i][3]*f;
    }
}

//----------------------------------------------------------------------------
unsigned long int vtkCamera::GetViewingRaysMTime()
{
  return this->ViewingRaysMTime.GetMTime();
}

//----------------------------------------------------------------------------
void vtkCamera::ViewingRaysModified()
{
  this->ViewingRaysMTime.Modified();
}

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

  os << indent << "ClippingRange: (" << this->ClippingRange[0] << ", " 
     << this->ClippingRange[1] << ")\n";
  os << indent << "DirectionOfProjection: (" << this->DirectionOfProjection[0]
     << ", " << this->DirectionOfProjection[1] 
     << ", " << this->DirectionOfProjection[2] << ")\n";
  os << indent << "Distance: " << this->Distance << "\n";
  os << indent << "EyeAngle: " << this->EyeAngle << "\n";
  os << indent << "FocalDisk: " << this->FocalDisk << "\n";
  os << indent << "FocalPoint: (" << this->FocalPoint[0] << ", " 
     << this->FocalPoint[1] << ", " << this->FocalPoint[2] << ")\n";
  os << indent << "ViewShear: (" << this->ViewShear[0]
     << ", " << this->ViewShear[1] 
     << ", " << this->ViewShear[2] << ")\n";
  os << indent << "ParallelProjection: " << 
    (this->ParallelProjection ? "On\n" : "Off\n");
  os << indent << "ParallelScale: " << this->ParallelScale << "\n";
  os << indent << "Position: (" << this->Position[0] << ", " 
     << this->Position[1] << ", " << this->Position[2] << ")\n";
  os << indent << "Stereo: " << (this->Stereo ? "On\n" : "Off\n");
  os << indent << "Thickness: " << this->Thickness << "\n";
  os << indent << "ViewAngle: " << this->ViewAngle << "\n";
  os << indent << "UseHorizontalViewAngle: " << this->UseHorizontalViewAngle << "\n";
  os << indent << "UserTransform: ";
  if (this->UserTransform)
    {
    os << this->UserTransform << "\n"; 
    }
  else
    {
    os << "(none)\n";
    }
  os << indent << "ViewPlaneNormal: (" << this->ViewPlaneNormal[0]
     << ", " << this->ViewPlaneNormal[1] 
     << ", " << this->ViewPlaneNormal[2] << ")\n";
  os << indent << "ViewUp: (" << this->ViewUp[0] << ", " 
     << this->ViewUp[1] << ", " << this->ViewUp[2] << ")\n";
  os << indent << "WindowCenter: (" << this->WindowCenter[0] << ", " 
     << this->WindowCenter[1] << ")\n";
}

vtkMatrix4x4 *vtkCamera::GetViewTransformMatrix() 
{ return this->ViewTransform->GetMatrix(); }

double *vtkCamera::GetOrientation() 
{ return this->ViewTransform->GetOrientation(); };

double *vtkCamera::GetOrientationWXYZ() 
{ return this->ViewTransform->GetOrientationWXYZ(); };