D:/VL/BuildSystem/VL_DISTRO/Visualization_Library_SDK/src/vlCore/math3D.cpp

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#include <vlCore/math3D.hpp>
#include <vlCore/AABB.hpp>
#include <vlCore/Vector2.hpp>
#include <vlCore/Vector4.hpp>
#include <vlCore/Plane.hpp>
#include <vlCore/checks.hpp>
#include <cstdlib>

using namespace vl;

//-----------------------------------------------------------------------------
Real vl::randomMinMax(Real min, Real max)
{
  Real t = rand() / (Real)RAND_MAX;
  return min + (max-min)*t;
}
//-----------------------------------------------------------------------------
int vl::greaterEqualPow2(int n)
{
  int pow2=2;
  for(int i=0; i<20; ++i) {
    if (pow2 >= n)
      return pow2;
    pow2 = pow2 * 2;
  }
  return pow2;
}
//-----------------------------------------------------------------------------
int vl::smallerEqualPow2(int n)
{
  int pow2=2;
  for(int i=0; i<20; ++i) {
    if (pow2 > n)
      return pow2/2;
    pow2 = pow2 * 2;
  }
  return pow2;
}
//-----------------------------------------------------------------------------
void vl::extractPlanes( Plane* planes, const mat4& modelviewproj )
{
  // see also http://www2.ravensoft.com/users/ggribb/plane%20extraction.pdf
  // see also http://zach.in.tu-clausthal.de/teaching/cg_literatur/lighthouse3d_view_frustum_culling/index.html
  // the equation is a*x+b*y+x*z+d = 0
  // where <a b c> is the normal of the plane
  // the normals are pointing inside the viewfrustum

  // 1) we want the planes to point outward so we reverse them
  // 2) because of 1) "d" becomes the distance of the plane from the origin

  vec3 n;
  Real d;

  // left clipping plane
  n.x() = modelviewproj.e(3,0) + modelviewproj.e(0,0);
  n.y() = modelviewproj.e(3,1) + modelviewproj.e(0,1);
  n.z() = modelviewproj.e(3,2) + modelviewproj.e(0,2);
  d = modelviewproj.e(3,3) + modelviewproj.e(0,3);
  d /= n.length();
  n.normalize();
  planes[0] = Plane(d,-n);

  // right clipping plane
  n.x() = modelviewproj.e(3,0) - modelviewproj.e(0,0);
  n.y() = modelviewproj.e(3,1) - modelviewproj.e(0,1);
  n.z() = modelviewproj.e(3,2) - modelviewproj.e(0,2);
  d = modelviewproj.e(3,3) - modelviewproj.e(0,3);
  d /= n.length();
  n.normalize();
  planes[1] = Plane(d,-n);

  // top clipping plane
  n.x() = modelviewproj.e(3,0) - modelviewproj.e(1,0);
  n.y() = modelviewproj.e(3,1) - modelviewproj.e(1,1);
  n.z() = modelviewproj.e(3,2) - modelviewproj.e(1,2);
  d = modelviewproj.e(3,3) - modelviewproj.e(1,3);
  d /= n.length();
  n.normalize();
  planes[2] = Plane(d,-n);

  // bottom clipping plane
  n.x() = modelviewproj.e(3,0) + modelviewproj.e(1,0);
  n.y() = modelviewproj.e(3,1) + modelviewproj.e(1,1);
  n.z() = modelviewproj.e(3,2) + modelviewproj.e(1,2);
  d = modelviewproj.e(3,3) + modelviewproj.e(1,3);
  d /= n.length();
  n.normalize();
  planes[3] = Plane(d,-n);

  // near clipping plane
  n.x() = modelviewproj.e(3,0) + modelviewproj.e(2,0);
  n.y() = modelviewproj.e(3,1) + modelviewproj.e(2,1);
  n.z() = modelviewproj.e(3,2) + modelviewproj.e(2,2);
  d = modelviewproj.e(3,3) + modelviewproj.e(2,3);
  d /= n.length();
  n.normalize();
  planes[4] = Plane(d,-n);

  // far clipping plane
  n.x() = modelviewproj.e(3,0) - modelviewproj.e(2,0);
  n.y() = modelviewproj.e(3,1) - modelviewproj.e(2,1);
  n.z() = modelviewproj.e(3,2) - modelviewproj.e(2,2);
  d = modelviewproj.e(3,3) - modelviewproj.e(2,3);
  d /= n.length();
  n.normalize();
  planes[5] = Plane(d,-n);
}