telinearfilter.cpp

海量地形数据漫游系统,对于OPENGL开发人员具有一定的参考

/*****************************************************************************\
 *
 * TeLinearFilter.cpp
 *
 * TeLinearFilter generator implementation
 *
 * Author: Martin Havl龛ek (xhavli15 AT stud.fit.vutbr.cz)
 * Contributors:
 *
 * ----------------------------------------------------------------------------
 *
 * THIS SOFTWARE IS NOT COPYRIGHTED
 *
 * This source code is offered for use in the public domain.
 * You may use, modify or distribute it freely.
 *
 * This source code is distributed in the hope that it will be useful but
 * WITHOUT ANY WARRANTY.  ALL WARRANTIES, EXPRESS OR IMPLIED ARE HEREBY
 * DISCLAIMED.  This includes but is not limited to warranties of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * If you find the source code useful, authors will kindly welcome
 * if you give them credit and keep their names with their source code.
 *
\*****************************************************************************/


#include "generators/TeLinearFilter.h"


//-----------------------------------------------------------------------------
/**
 * Constructor.
 *
 * Sets default generator parameters and resets the step counter.
 */
TeLinearFilter::TeLinearFilter()
{
  this->setDefaults();
  this->reset();
}


//-----------------------------------------------------------------------------
/**
 * Sets default generator parameters.
 */
void TeLinearFilter::setDefaults()
{
  hmap = NULL;
  stepNum = 0; // not used by this generator
  _times = times = 5;
  _coef = coef = 0.90f;
}


//-----------------------------------------------------------------------------
/**
 * Updates private parameters to fit theirs public images.
 *
 * I call this "delayed setting". It ensures, that correct attributes
 * are used for the current task (the private ones). When the task is done,
 * private attributes are updated to match the public ones and then will be
 * used for the next task.
 *
 * User doesn't need to worry about this, because this method is called
 * internally from generate() and genStep() functions.
 *
 * \sa times, coef
 */
void TeLinearFilter::updateParams()
{
  _times = times;
  _coef = coef;
}


//-----------------------------------------------------------------------------
/**
 * In-One-Step generation.
 *
 * The whole generation will be done in one function call.
 *
 * Calling updateParams() should be the first thing done here. It calls
 * original TeHeightMap::filter_Linear() method.
 */
void TeLinearFilter::generate()
{
  this->updateParams();
  hmap->filter_Linear(_coef, _times);
}


//-----------------------------------------------------------------------------
/**
 * One step of the generation algorithm.
 *
 * Calling updateParams() should be the first thing done in the first run.
 * reset() and TeHeightMap::resetFlags() should be called before returning
 * TRUE.
 *
 * \return TRUE if generation finished and object is ready, FALSE otherwise.
 *
 * \todo Generation should be controlled by stepNum attribute. This one
 *       should be dynamically updated according to system performance.
 */
SbBool TeLinearFilter::genStep()
{
  static int resx, resy;

  switch (step) {
     case 0: // init
             this->updateParams();
             hmap->getResolution(resx, resy);
             step++;
             break;
    default: // loop
             if (step<_times) {
               int x = 0;
               int y = 0;

               // rows
               for (y=0; y<resy; y++) {
                 // from left to right
                 x = 1;
                 while (x < resx-1) {
                   hmap->values[(y*resx)+x] = hmap->values[(y*resx)+x-1]*(1-coef)+hmap->values[(y*resx)+x]*coef;
                   x++;
                 }
                 // from right to left
                 x = resx-2;
                 while (x > -1) {
                   hmap->values[(y*resx)+x] = hmap->values[(y*resx)+x+1]*(1-coef)+hmap->values[(y*resx)+x]*coef;
                 x--;
                 }
               }

               // columns
               for(x=0; x<resx; x++) {
                 // columns top to bottom
                 y = 1;
                 while (y < resy) {
                   hmap->values[(y*resx)+x] = hmap->values[((y-1)*resx)+x]*(1-coef)+hmap->values[(y*resx)+x]*coef;
                   y++;
                 }
                 // columns bottom to top
                 y = resy-2;
                 while (y > -1) {
                   hmap->values[(y*resx)+x] = hmap->values[((y+1)*resx)+x]*(1-coef)+hmap->values[(y*resx)+x]*coef;
                   y--;
                 }
               }

               step++;
             }
             else {
               hmap->resetFlags();
               this->reset();
               return TRUE;
             }
             break;
  }
  return FALSE;
}