/home/master/UCL/VisualizationLibrary/src/vlGraphics/PixelLODEvaluator.cpp

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/*  Visualization Library                                                             */
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#include <vlGraphics/PixelLODEvaluator.hpp>
#include <vlGraphics/Camera.hpp>

using namespace vl;

//-----------------------------------------------------------------------------
int PixelLODEvaluator::evaluate(Actor* actor, Camera* camera)
{
  if (mPixelRangeSet.empty())
    return 0;

  AABB aabb = actor->transform() ? actor->lod(0)->boundingBox().transformed( actor->transform()->worldMatrix() ) : actor->lod(0)->boundingBox();

  vec3 corner[] = 
  {
    vec3(aabb.minCorner().x(), aabb.minCorner().y(), aabb.minCorner().z()),
    vec3(aabb.minCorner().x(), aabb.maxCorner().y(), aabb.minCorner().z()),
    vec3(aabb.maxCorner().x(), aabb.maxCorner().y(), aabb.minCorner().z()),
    vec3(aabb.maxCorner().x(), aabb.minCorner().y(), aabb.minCorner().z()),
    vec3(aabb.minCorner().x(), aabb.minCorner().y(), aabb.maxCorner().z()),
    vec3(aabb.minCorner().x(), aabb.maxCorner().y(), aabb.maxCorner().z()),
    vec3(aabb.maxCorner().x(), aabb.maxCorner().y(), aabb.maxCorner().z()),
    vec3(aabb.maxCorner().x(), aabb.minCorner().y(), aabb.maxCorner().z())
  };

  mat4 proj_matrix = camera->projectionMatrix() * camera->viewMatrix();

  aabb.setNull();

  // project the 8 corners in the viewport
  for(int i=0; i<8; ++i)
  {
    vec4 out = proj_matrix * vec4(corner[i],1);

    if (out.w() == 0.0f)
      continue;

    out.x() /= out.w();
    out.y() /= out.w();
    out.z() /= out.w();

    // map to range 0-1
    out.x() = out.x() * 0.5f + 0.5f;
    out.y() = out.y() * 0.5f + 0.5f;
    out.z() = out.z() * 0.5f + 0.5f;

    // map to viewport
    out.x() = out.x() * camera->viewport()->width()  + camera->viewport()->x();
    out.y() = out.y() * camera->viewport()->height() + camera->viewport()->y();

    aabb.addPoint(out.xyz());
  }

  double pixels = aabb.width() * aabb.height();

  // we assume the distances are sorted in increasing order
  int i=0;
  for(; i<(int)mPixelRangeSet.size(); ++i)
  {
    if (pixels>mPixelRangeSet[mPixelRangeSet.size() - 1 - i])
      return i;
  }

  return i; // == mPixelRangeSet.size()
}
//-----------------------------------------------------------------------------