vtkFixedPointVolumeRayCastCompositeShadeHelper.cxx

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

  Program:   Visualization Toolkit
  Module:    vtkFixedPointVolumeRayCastCompositeShadeHelper.cxx
  Language:  C++

  Copyright (c) 1993-2002 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 "vtkFixedPointVolumeRayCastCompositeShadeHelper.h"

#include "vtkImageData.h"
#include "vtkCommand.h"
#include "vtkFixedPointVolumeRayCastMapper.h"
#include "vtkObjectFactory.h"
#include "vtkRenderWindow.h"
#include "vtkVolume.h"
#include "vtkVolumeProperty.h"
#include "vtkFixedPointRayCastImage.h"
#include "vtkDataArray.h"

#include <cmath>

vtkStandardNewMacro(vtkFixedPointVolumeRayCastCompositeShadeHelper);

// Construct a new vtkFixedPointVolumeRayCastCompositeShadeHelper with default values
vtkFixedPointVolumeRayCastCompositeShadeHelper::vtkFixedPointVolumeRayCastCompositeShadeHelper()
{
}

// Destruct a vtkFixedPointVolumeRayCastCompositeShadeHelper - clean up any memory used
vtkFixedPointVolumeRayCastCompositeShadeHelper::~vtkFixedPointVolumeRayCastCompositeShadeHelper()
{
}


// This method is used when the interpolation type is nearest neighbor and
// the data has one component and scale == 1.0 and shift == 0.0. In the inner
// loop we get the data value as an unsigned short, and use this index to
// lookup a color and opacity for this sample. We then composite this into
// the color computed so far along the ray, and check if we can terminate at
// this point (if the accumulated opacity is higher than some threshold).
// Finally we move on to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageOneSimpleNN( T *data,
                                                   int threadID,
                                                   int threadCount,
                                                   vtkFixedPointVolumeRayCastMapper *mapper,
                                                   vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeNN();
  VTKKWRCHelper_InitializeCompositeOneNN();
  VTKKWRCHelper_InitializeCompositeShadeNN();
  VTKKWRCHelper_SpaceLeapSetup();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      VTKKWRCHelper_MoveToNextSampleShadeNN();
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckNN( pos );

    unsigned short val    = static_cast<unsigned short>(((*dptr)));
    VTKKWRCHelper_LookupColorUS( colorTable[0], scalarOpacityTable[0], val, tmp );
    if (tmp[3])
    {
      unsigned short normal = *dirPtr;
      VTKKWRCHelper_LookupShading( diffuseShadingTable[0], specularShadingTable[0], normal, tmp );
      VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
    }
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is nearest neighbor and
// the data has one component. In the inner loop we get the data value as
// an unsigned short using the scale/shift, and use this index to lookup
// a color and opacity for this sample. We then composite this into the
// color computed so far along the ray, and check if we can terminate at
// this point (if the accumulated opacity is higher than some threshold).
// Finally we move on to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageOneNN( T *data,
                                             int threadID,
                                             int threadCount,
                                             vtkFixedPointVolumeRayCastMapper *mapper,
                                             vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeNN();
  VTKKWRCHelper_InitializeCompositeOneNN();
  VTKKWRCHelper_InitializeCompositeShadeNN();
  VTKKWRCHelper_SpaceLeapSetup();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      VTKKWRCHelper_MoveToNextSampleShadeNN();
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckNN( pos );

    unsigned short val    = static_cast<unsigned short>(((*dptr) + shift[0])*scale[0]);
    VTKKWRCHelper_LookupColorUS( colorTable[0], scalarOpacityTable[0], val, tmp );
    if (tmp[3])
    {
      unsigned short normal = *dirPtr;
      VTKKWRCHelper_LookupShading( diffuseShadingTable[0], specularShadingTable[0], normal, tmp );
      VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
    }
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}


// This method is used when the interpolation type is nearest neighbor and
// the data has two components which are not considered independent. In the
// inner loop we compute the two unsigned short index values from the data
// values (using the scale/shift). We use the first index to lookup a color,
// and we use the second index to look up the opacity. We then composite
// the color into the color computed so far along this ray, and check to
// see if we can terminate here (if the opacity accumulated exceed some
// threshold). Finally we move to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageTwoDependentNN( T *data,
                                                      int threadID,
                                                      int threadCount,
                                                      vtkFixedPointVolumeRayCastMapper *mapper,
                                                      vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeNN();
  VTKKWRCHelper_InitializeCompositeOneNN();
  VTKKWRCHelper_InitializeCompositeShadeNN();
  VTKKWRCHelper_SpaceLeapSetup();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      VTKKWRCHelper_MoveToNextSampleShadeNN();
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckNN( pos );

    unsigned short val[2];
    val[0] = static_cast<unsigned short>(((*(dptr  )) + shift[0])*scale[0]);
    val[1] = static_cast<unsigned short>(((*(dptr+1)) + shift[1])*scale[1]);

    tmp[3] = scalarOpacityTable[0][val[1]];
    if (tmp[3])
    {
      tmp[0] = static_cast<unsigned short>
        ((colorTable[0][3*val[0]  ]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));
      tmp[1] = static_cast<unsigned short>
        ((colorTable[0][3*val[0]+1]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));
      tmp[2] = static_cast<unsigned short>
        ((colorTable[0][3*val[0]+2]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));

      unsigned short normal = *dirPtr;
      VTKKWRCHelper_LookupShading( diffuseShadingTable[0], specularShadingTable[0], normal, tmp );
      VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
    }
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is nearest neighbor and
// the data has four components which are not considered independent . This
// means that the first three components directly represent color, and this
// data must be of unsigned char type. In the inner loop we directly access
// the four data values (no scale/shift is needed). The first three are the
// color of this sample and the fourth is used to look up an opacity in the
// scalar opacity transfer function. We then composite this color into the
// color we have accumulated so far along the ray, and check if we can
// terminate here (if our accumulated opacity has exceed some threshold).
// Finally we move onto the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageFourDependentNN( T *data,
                                                       int threadID,
                                                       int threadCount,
                                                       vtkFixedPointVolumeRayCastMapper *mapper,
                                                       vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeNN();
  VTKKWRCHelper_InitializeCompositeOneNN();
  VTKKWRCHelper_InitializeCompositeShadeNN();
  VTKKWRCHelper_SpaceLeapSetup();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      VTKKWRCHelper_MoveToNextSampleShadeNN();
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckNN( pos );

    unsigned short val[4];
    val[0] = *(dptr  );
    val[1] = *(dptr+1);
    val[2] = *(dptr+2);
    val[3] = static_cast<unsigned short>(((*(dptr+3)) + shift[3])*scale[3]);

    tmp[3] = scalarOpacityTable[0][val[3]];
    if ( tmp[3] )
    {
      tmp[0] = (val[0]*tmp[3]+0x7f)>>(8);
      tmp[1] = (val[1]*tmp[3]+0x7f)>>(8);
      tmp[2] = (val[2]*tmp[3]+0x7f)>>(8);

      unsigned short normal   = *dirPtr;
      VTKKWRCHelper_LookupShading( diffuseShadingTable[0], specularShadingTable[0], normal, tmp );
      VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
    }
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is nearest neighbor and
// the data has more than one component and the components are considered to
// be independent. In the inner loop we access each component value, using
// the scale/shift to turn the data value into an unsigned short index. We
// then lookup the color/opacity for each component and combine them according
// to the weighting value for each component. We composite this resulting
// color into the color already accumulated for this ray, and we check
// whether we can terminate here (if the accumulated opacity exceeds some
// threshold). Finally we increment to the next sample on the ray.
//
// TODO: short circuit calculations when opacity is 0
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageIndependentNN( T *data,
                                                     int threadID,
                                                     int threadCount,
                                                     vtkFixedPointVolumeRayCastMapper *mapper,
                                                     vtkVolume *vol)
{
  VTKKWRCHelper_InitializeWeights();
  VTKKWRCHelper_InitializationAndLoopStartShadeNN();
  VTKKWRCHelper_InitializeCompositeMultiNN();
  VTKKWRCHelper_InitializeCompositeShadeNN();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      VTKKWRCHelper_MoveToNextSampleShadeNN();
    }

    VTKKWRCHelper_CroppingCheckNN( pos );

    unsigned short normal[4];
    for ( c = 0; c < components; c++ )
    {
      val[c]    = static_cast<unsigned short>(((*(dptr+c)) + shift[c])*scale[c]);
      normal[c] = *(dirPtr+c);
    }

    VTKKWRCHelper_LookupAndCombineIndependentColorsShadeUS( colorTable, scalarOpacityTable,
                                                            diffuseShadingTable,
                                                            specularShadingTable,
                                                            val, normal, weights,
                                                            components, tmp );

    if ( tmp[3] )
    {
      VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
    }
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is linear and the data
// has one component and scale = 1.0 and shift = 0.0. In the inner loop we
// get the data value for the eight cell corners (if we have changed cells)
// as an unsigned short (the range must be right and we don't need the
// scale/shift). We compute our weights within the cell according to our
// fractional position within the cell, apply trilinear interpolation to
// compute the index, and use this index to lookup a color and opacity for
// this sample. We then composite this into the color computed so far along
// the ray, and check if we can terminate at this point (if the accumulated
// opacity is higher than some threshold). Finally we move on to the next
// sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageOneSimpleTrilin( T *data,
                                                       int threadID,
                                                       int threadCount,
                                                       vtkFixedPointVolumeRayCastMapper *mapper,
                                                       vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeTrilin();
  VTKKWRCHelper_InitializeCompositeOneTrilin();
  VTKKWRCHelper_InitializeCompositeOneShadeTrilin();
  VTKKWRCHelper_SpaceLeapSetup();

  int needToSampleDirection = 0;
  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      mapper->FixedPointIncrement( pos, dir );
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckTrilin( pos );

    mapper->ShiftVectorDown( pos, spos );
    if ( spos[0] != oldSPos[0] ||
         spos[1] != oldSPos[1] ||
         spos[2] != oldSPos[2] )
    {
      oldSPos[0] = spos[0];
      oldSPos[1] = spos[1];
      oldSPos[2] = spos[2];

      dptr = data + spos[0]*inc[0] + spos[1]*inc[1] + spos[2]*inc[2];
      VTKKWRCHelper_GetCellScalarValuesSimple( dptr );
      dirPtrABCD = gradientDir[spos[2]  ] + spos[0]*dInc[0] + spos[1]*dInc[1];
      dirPtrEFGH = gradientDir[spos[2]+1] + spos[0]*dInc[0] + spos[1]*dInc[1];
      needToSampleDirection = 1;
    }

    VTKKWRCHelper_ComputeWeights(pos);
    VTKKWRCHelper_InterpolateScalar(val);

    VTKKWRCHelper_LookupColorUS( colorTable[0], scalarOpacityTable[0], val, tmp );
    if ( needToSampleDirection )
    {
      VTKKWRCHelper_GetCellDirectionValues( dirPtrABCD, dirPtrEFGH );
      needToSampleDirection = 0;
    }

    VTKKWRCHelper_InterpolateShading( diffuseShadingTable[0], specularShadingTable[0], tmp );
    VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is linear and the data
// has one component and scale != 1.0 or shift != 0.0. In the inner loop we
// get the data value for the eight cell corners (if we have changed cells)
// as an unsigned short (we use the scale/shift to ensure the correct range).
// We compute our weights within the cell according to our fractional position
// within the cell, apply trilinear interpolation to compute the index, and use
// this index to lookup a color and opacity for this sample. We then composite
// this into the color computed so far along the ray, and check if we can
// terminate at this point (if the accumulated opacity is higher than some
// threshold). Finally we move on to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageOneTrilin( T *data,
                                                 int threadID,
                                                 int threadCount,
                                                 vtkFixedPointVolumeRayCastMapper *mapper,
                                                 vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeTrilin();
  VTKKWRCHelper_InitializeCompositeOneTrilin();
  VTKKWRCHelper_InitializeCompositeOneShadeTrilin();
  VTKKWRCHelper_SpaceLeapSetup();

  int needToSampleDirection = 0;
  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      mapper->FixedPointIncrement( pos, dir );
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckTrilin( pos );

    mapper->ShiftVectorDown( pos, spos );
    if ( spos[0] != oldSPos[0] ||
         spos[1] != oldSPos[1] ||
         spos[2] != oldSPos[2] )
    {
      oldSPos[0] = spos[0];
      oldSPos[1] = spos[1];
      oldSPos[2] = spos[2];


      dptr = data + spos[0]*inc[0] + spos[1]*inc[1] + spos[2]*inc[2];
      VTKKWRCHelper_GetCellScalarValues( dptr, scale[0], shift[0] );
      dirPtrABCD = gradientDir[spos[2]  ] + spos[0]*dInc[0] + spos[1]*dInc[1];
      dirPtrEFGH = gradientDir[spos[2]+1] + spos[0]*dInc[0] + spos[1]*dInc[1];
      needToSampleDirection = 1;
    }

    VTKKWRCHelper_ComputeWeights(pos);
    VTKKWRCHelper_InterpolateScalar(val);

    VTKKWRCHelper_LookupColorUS( colorTable[0], scalarOpacityTable[0], val, tmp );
    if ( needToSampleDirection )
    {
      VTKKWRCHelper_GetCellDirectionValues( dirPtrABCD, dirPtrEFGH );
      needToSampleDirection = 0;
    }
    VTKKWRCHelper_InterpolateShading( diffuseShadingTable[0], specularShadingTable[0], tmp );
    VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}


// This method is used when the interpolation type is linear, the data has
// two components and the components are not considered independent. In the
// inner loop we get the data value for the eight cell corners (if we have
// changed cells) for both components as an unsigned shorts (we use the
// scale/shift to ensure the correct range). We compute our weights within
// the cell according to our fractional position within the cell, and apply
// trilinear interpolation to compute the two index value. We use the first
// index to lookup a color and the second to look up an opacity for this sample.
// We then composite this into the color computed so far along the ray, and
// check if we can terminate at this point (if the accumulated opacity is
// higher than some threshold). Finally we move on to the next sample along
// the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageTwoDependentTrilin( T *data,
                                                          int threadID,
                                                          int threadCount,
                                                          vtkFixedPointVolumeRayCastMapper *mapper,
                                                          vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeTrilin();
  VTKKWRCHelper_InitializeCompositeMultiTrilin();
  VTKKWRCHelper_InitializeCompositeOneShadeTrilin();
  VTKKWRCHelper_SpaceLeapSetup();

  int needToSampleDirection = 0;
  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      mapper->FixedPointIncrement( pos, dir );
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckTrilin( pos );

    mapper->ShiftVectorDown( pos, spos );
    if ( spos[0] != oldSPos[0] ||
         spos[1] != oldSPos[1] ||
         spos[2] != oldSPos[2] )
    {
      oldSPos[0] = spos[0];
      oldSPos[1] = spos[1];
      oldSPos[2] = spos[2];

      dptr = data + spos[0]*inc[0] + spos[1]*inc[1] + spos[2]*inc[2];
      VTKKWRCHelper_GetCellComponentScalarValues( dptr, 0, scale[0], shift[0] );

      dptr++;
      VTKKWRCHelper_GetCellComponentScalarValues( dptr, 1, scale[1], shift[1] );

      dirPtrABCD = gradientDir[spos[2]  ] + spos[0]*dInc[0] + spos[1]*dInc[1];
      dirPtrEFGH = gradientDir[spos[2]+1] + spos[0]*dInc[0] + spos[1]*dInc[1];
      needToSampleDirection = 1;
    }

    VTKKWRCHelper_ComputeWeights(pos);
    VTKKWRCHelper_InterpolateScalarComponent( val, c, 2 );

    tmp[3] = scalarOpacityTable[0][val[1]];
    if ( !tmp[3] )
    {
      continue;
    }

    if ( needToSampleDirection )
    {
      VTKKWRCHelper_GetCellDirectionValues( dirPtrABCD, dirPtrEFGH );
      needToSampleDirection = 0;
    }

    tmp[0] = static_cast<unsigned short>
      ((colorTable[0][3*val[0]  ]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));
    tmp[1] = static_cast<unsigned short>
      ((colorTable[0][3*val[0]+1]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));
    tmp[2] = static_cast<unsigned short>
      ((colorTable[0][3*val[0]+2]*tmp[3] + 0x7fff)>>(VTKKW_FP_SHIFT));

    VTKKWRCHelper_InterpolateShading( diffuseShadingTable[0], specularShadingTable[0], tmp );
    VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );

  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}



// This method is used when the interpolation type is linear, the data has
// four components and the components are not considered independent. In the
// inner loop we get the data value for the eight cell corners (if we have
// changed cells) for all components as an unsigned shorts (we don't have to
// use the scale/shift because only unsigned char data is supported for four
// component data when the components are not independent). We compute our
// weights within the cell according to our fractional position within the cell,
// and apply trilinear interpolation to compute a value for each component. We
// use the first three directly as the color of the sample, and the fourth is
// used to look up an opacity for this sample. We then composite this into the
// color computed so far along the ray, and check if we can terminate at this
// point (if the accumulated opacity is higher than some threshold). Finally we
// move on to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageFourDependentTrilin( T *data,
                                                           int threadID,
                                                           int threadCount,
                                                           vtkFixedPointVolumeRayCastMapper *mapper,
                                                           vtkVolume *vol)
{
  VTKKWRCHelper_InitializationAndLoopStartShadeTrilin();
  VTKKWRCHelper_InitializeCompositeMultiTrilin();
  VTKKWRCHelper_InitializeCompositeOneShadeTrilin();
  VTKKWRCHelper_SpaceLeapSetup();

  int needToSampleDirection = 0;
  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      mapper->FixedPointIncrement( pos, dir );
    }

    VTKKWRCHelper_SpaceLeapCheck();
    VTKKWRCHelper_CroppingCheckTrilin( pos );

    mapper->ShiftVectorDown( pos, spos );
    if ( spos[0] != oldSPos[0] ||
         spos[1] != oldSPos[1] ||
         spos[2] != oldSPos[2] )
    {
      oldSPos[0] = spos[0];
      oldSPos[1] = spos[1];
      oldSPos[2] = spos[2];

      dptr = data + spos[0]*inc[0] + spos[1]*inc[1] + spos[2]*inc[2];
      VTKKWRCHelper_GetCellComponentRawScalarValues( dptr, 0 );

      dptr++;
      VTKKWRCHelper_GetCellComponentRawScalarValues( dptr, 1 );

      dptr++;
      VTKKWRCHelper_GetCellComponentRawScalarValues( dptr, 2 );

      dptr++;
      VTKKWRCHelper_GetCellComponentScalarValues( dptr, 3, scale[3], shift[3] );

      dirPtrABCD = gradientDir[spos[2]  ] + spos[0]*dInc[0] + spos[1]*dInc[1];
      dirPtrEFGH = gradientDir[spos[2]+1] + spos[0]*dInc[0] + spos[1]*dInc[1];
      needToSampleDirection = 1;
    }

    VTKKWRCHelper_ComputeWeights(pos);
    VTKKWRCHelper_InterpolateScalarComponent( val, c, 4 );

    tmp[3] = scalarOpacityTable[0][val[3]];
    if ( !tmp[3] )
    {
      continue;
    }

    if ( needToSampleDirection )
    {
      VTKKWRCHelper_GetCellDirectionValues( dirPtrABCD, dirPtrEFGH );
      needToSampleDirection = 0;
    }

    tmp[0] = (val[0]*tmp[3]+0x7f)>>8;
    tmp[1] = (val[1]*tmp[3]+0x7f)>>8;
    tmp[2] = (val[2]*tmp[3]+0x7f)>>8;

    VTKKWRCHelper_InterpolateShading( diffuseShadingTable[0], specularShadingTable[0], tmp );
    VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}

// This method is used when the interpolation type is linear, the data has
// more than one component and the components are considered independent. In
// the inner loop we get the data value for the eight cell corners (if we have
// changed cells) for all components as an unsigned shorts (we have to use the
// scale/shift to ensure that we obtained unsigned short indices) We compute our
// weights within the cell according to our fractional position within the cell,
// and apply trilinear interpolation to compute a value for each component. We
// look up a color/opacity for each component and blend them according to the
// component weights. We then composite this resulting color into the
// color computed so far along the ray, and check if we can terminate at this
// point (if the accumulated opacity is higher than some threshold). Finally we
// move on to the next sample along the ray.
template <class T>
void vtkFixedPointCompositeShadeHelperGenerateImageIndependentTrilin( T *data,
                                                         int threadID,
                                                         int threadCount,
                                                         vtkFixedPointVolumeRayCastMapper *mapper,
                                                         vtkVolume *vol)
{
  VTKKWRCHelper_InitializeWeights();
  VTKKWRCHelper_InitializationAndLoopStartShadeTrilin();
  VTKKWRCHelper_InitializeCompositeMultiTrilin();
  VTKKWRCHelper_InitializeCompositeMultiShadeTrilin();

  for ( k = 0; k < numSteps; k++ )
  {
    if ( k )
    {
      mapper->FixedPointIncrement( pos, dir );
    }

    VTKKWRCHelper_CroppingCheckTrilin( pos );

    mapper->ShiftVectorDown( pos, spos );
    if ( spos[0] != oldSPos[0] ||
         spos[1] != oldSPos[1] ||
         spos[2] != oldSPos[2] )
    {
      oldSPos[0] = spos[0];
      oldSPos[1] = spos[1];
      oldSPos[2] = spos[2];

      dptr = data + spos[0]*inc[0] + spos[1]*inc[1] + spos[2]*inc[2];
      VTKKWRCHelper_GetCellComponentScalarValues( dptr, 0, scale[0], shift[0] );

      dptr++;
      VTKKWRCHelper_GetCellComponentScalarValues( dptr, 1, scale[1], shift[1] );

      if ( components > 2 )
      {
        dptr++;
        VTKKWRCHelper_GetCellComponentScalarValues( dptr, 2, scale[2], shift[2] );
        if ( components > 3 )
        {
          dptr++;
          VTKKWRCHelper_GetCellComponentScalarValues( dptr, 3, scale[3], shift[3] );
        }
      }


      dirPtrABCD = gradientDir[spos[2]  ] + spos[0]*dInc[0] + spos[1]*dInc[1];
      dirPtrEFGH = gradientDir[spos[2]+1] + spos[0]*dInc[0] + spos[1]*dInc[1];
      VTKKWRCHelper_GetCellComponentDirectionValues( dirPtrABCD, dirPtrEFGH, 0 );

      dirPtrABCD++;
      dirPtrEFGH++;
      VTKKWRCHelper_GetCellComponentDirectionValues( dirPtrABCD, dirPtrEFGH, 1 );

      if ( components > 2 )
      {
        dirPtrABCD++;
        dirPtrEFGH++;
        VTKKWRCHelper_GetCellComponentDirectionValues( dirPtrABCD, dirPtrEFGH, 2 );
        if ( components > 3 )
        {
          dirPtrABCD++;
          dirPtrEFGH++;
          VTKKWRCHelper_GetCellComponentDirectionValues( dirPtrABCD, dirPtrEFGH, 3 );
        }
      }
    }

    VTKKWRCHelper_ComputeWeights(pos);
    VTKKWRCHelper_InterpolateScalarComponent( val, c, components );

    VTKKWRCHelper_LookupAndCombineIndependentColorsInterpolateShadeUS(
      colorTable, scalarOpacityTable, diffuseShadingTable,
      specularShadingTable, val, weights, components, tmp );

    VTKKWRCHelper_CompositeColorAndCheckEarlyTermination( color, tmp, remainingOpacity );
  }

  VTKKWRCHelper_SetPixelColor( imagePtr, color, remainingOpacity );
  VTKKWRCHelper_IncrementAndLoopEnd();
}


void vtkFixedPointVolumeRayCastCompositeShadeHelper::GenerateImage(
  int threadID,
  int threadCount,
  vtkVolume *vol,
  vtkFixedPointVolumeRayCastMapper *mapper )
{
  void *data     = mapper->GetCurrentScalars()->GetVoidPointer(0);
  int scalarType = mapper->GetCurrentScalars()->GetDataType();

  // Nearest Neighbor interpolate
  if ( mapper->ShouldUseNearestNeighborInterpolation( vol ) )
  {
    // One component data
    if ( mapper->GetCurrentScalars()->GetNumberOfComponents() == 1 )
    {
      // Scale == 1.0 and shift == 0.0 - simple case (faster)
      if ( mapper->GetTableScale()[0] == 1.0 &&
           mapper->GetTableShift()[0] == 0.0 )
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageOneSimpleNN(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
      else
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageOneNN(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
    }
    // More that one independent components
    else if ( vol->GetProperty()->GetIndependentComponents() )
    {
      switch ( scalarType )
      {
        vtkTemplateMacro(
          vtkFixedPointCompositeShadeHelperGenerateImageIndependentNN(
            static_cast<VTK_TT *>(data),
            threadID, threadCount, mapper, vol) );
      }
    }
    // Dependent (color) components
    else
    {
      // Two components - the first specifies color (through a lookup table)
      // and the second specified opacity (through a lookup table)
      if ( mapper->GetCurrentScalars()->GetNumberOfComponents() == 2 )
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageTwoDependentNN(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
      // Four components - they must be unsigned char, the first three directly
      // specify color and the fourth specifies opacity (through a lookup
      // table)
      else
      {
        if ( scalarType == VTK_UNSIGNED_CHAR )
        {
          vtkFixedPointCompositeShadeHelperGenerateImageFourDependentNN(
            static_cast<unsigned char *>(data), threadID, threadCount, mapper,
            vol );
        }
        else
        {
          vtkErrorMacro("Four component dependent data must be unsigned char");
        }
      }
    }
  }
  // Trilinear Interpolation
  else
  {
    // One component
    if ( mapper->GetCurrentScalars()->GetNumberOfComponents() == 1 )
    {
      // Scale == 1.0 and shift == 0.0 - simple case (faster)
      if ( mapper->GetTableScale()[0] == 1.0 &&
           mapper->GetTableShift()[0] == 0.0 )
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageOneSimpleTrilin(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
      // Scale != 1.0 or shift != 0.0 - must apply scale/shift in inner loop
      else
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageOneTrilin(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
    }
    // Indepedent components (more than one)
    else if ( vol->GetProperty()->GetIndependentComponents() )
    {
      switch ( scalarType )
      {
        vtkTemplateMacro(
          vtkFixedPointCompositeShadeHelperGenerateImageIndependentTrilin(
            static_cast<VTK_TT *>(data),
            threadID, threadCount, mapper, vol) );
      }
    }
    // Dependent components
    else
    {
      // Two components - the first specifies color (through a lookup table)
      // and the second specified opacity (through a lookup table)
      if ( mapper->GetCurrentScalars()->GetNumberOfComponents() == 2 )
      {
        switch ( scalarType )
        {
          vtkTemplateMacro(
            vtkFixedPointCompositeShadeHelperGenerateImageTwoDependentTrilin(
              static_cast<VTK_TT *>(data),
              threadID, threadCount, mapper, vol) );
        }
      }
      // Four components - they must be unsigned char, the first three directly
      // specify color and the fourth specifies opacity (through a lookup
      // table)
      else
      {
        if ( scalarType == VTK_UNSIGNED_CHAR )
        {
          vtkFixedPointCompositeShadeHelperGenerateImageFourDependentTrilin(
            static_cast<unsigned char *>(data), threadID, threadCount, mapper,
            vol );
        }
        else
        {
          vtkErrorMacro("Four component dependent data must be unsigned char");
        }
      }
    }
  }
}

// Print method for vtkFixedPointVolumeRayCastCompositeShadeHelper
void vtkFixedPointVolumeRayCastCompositeShadeHelper::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);
}