FrustumClassification.cpp

#include "Foundation/Logging/Logger.h"
#include "Utilities/FrustumClassification.h"
 
#include <glm/gtc/packing.hpp>
 
namespace {
  Cogs::Logging::Log logger = Cogs::Logging::getLogger("FrustumClassification");
}
 
Cogs::Core::FrustumPlanes Cogs::Core::frustumClassifyBoundingBox(const glm::mat4& localToClip,
                                                                 const glm::vec3& min,
                                                                 const glm::vec3& max,
                                                                 const float discardThreshold,
                                                                 const float keepThreshold)
{
  FrustumPlanes retval = FrustumPlanes::InsideNone;
 
  float lx[2], ly[2];
 
  for (int i = 0; i < 8; i++) {
    glm::vec3 p((i & 1) ? min.x : max.x,
      (i & 2) ? min.y : max.y,
                (i & 4) ? min.z : max.z);
    glm::vec4 h = localToClip * glm::vec4(p.x, p.y, p.z, 1.f);
    retval |= (h.x <= h.w ? FrustumPlanes::InsidePosX : FrustumPlanes::InsideNone) |
      (-h.w <= h.x ? FrustumPlanes::InsideNegX : FrustumPlanes::InsideNone) |
      (h.y <= h.w ? FrustumPlanes::InsidePosY : FrustumPlanes::InsideNone) |
      (-h.w <= h.y ? FrustumPlanes::InsideNegY : FrustumPlanes::InsideNone) |
      (h.z <= h.w ? FrustumPlanes::InsidePosZ : FrustumPlanes::InsideNone) |
      (-h.w <= h.z ? FrustumPlanes::InsideNegZ : FrustumPlanes::InsideNone);
    float rcp_w = 1.f / h.w;
    float px = rcp_w * h.x;
    float py = rcp_w * h.y;
    lx[0] = ((i == 0) || (px < lx[0])) ? px : lx[0];
    lx[1] = ((i == 0) || (lx[1] < px)) ? px : lx[1];
    ly[0] = ((i == 0) || (py < ly[0])) ? py : ly[0];
    ly[1] = ((i == 0) || (ly[1] < py)) ? py : ly[1];
  }
  bool discard = (lx[1] - lx[0])*(ly[1] - ly[0]) < discardThreshold;
  if (discard) {
    auto diff = max - min;
    if (glm::any(glm::greaterThan(diff, glm::vec3(keepThreshold)))) {
      discard = false;
    }
  }
  return discard ? FrustumPlanes::InsideNone : retval;
}
 
Cogs::Core::FrustumPlanes Cogs::Core::frustumClassifyBoundingBox(const glm::mat4& localToClip,
                                                                 const glm::vec3& min,
                                                                 const glm::vec3& max)
{
  FrustumPlanes retval = FrustumPlanes::InsideNone;
  for (int i = 0; i < 8; i++) {
    glm::vec3 p((i & 1) ? min.x : max.x,
      (i & 2) ? min.y : max.y,
                (i & 4) ? min.z : max.z);
    glm::vec4 h = localToClip * glm::vec4(p.x, p.y, p.z, 1.f);
    retval |= (h.x <= h.w ? FrustumPlanes::InsidePosX : FrustumPlanes::InsideNone) |
      (-h.w <= h.x ? FrustumPlanes::InsideNegX : FrustumPlanes::InsideNone) |
      (h.y <= h.w ? FrustumPlanes::InsidePosY : FrustumPlanes::InsideNone) |
      (-h.w <= h.y ? FrustumPlanes::InsideNegY : FrustumPlanes::InsideNone) |
      (h.z <= h.w ? FrustumPlanes::InsidePosZ : FrustumPlanes::InsideNone) |
      (-h.w <= h.z ? FrustumPlanes::InsideNegZ : FrustumPlanes::InsideNone);
  }
  return retval;
}