Line data    Source code

       1             : /* Copyright (C) 2019 Wildfire Games.
       2             :  * This file is part of 0 A.D.
       3             :  *
       4             :  * 0 A.D. is free software: you can redistribute it and/or modify
       5             :  * it under the terms of the GNU General Public License as published by
       6             :  * the Free Software Foundation, either version 2 of the License, or
       7             :  * (at your option) any later version.
       8             :  *
       9             :  * 0 A.D. is distributed in the hope that it will be useful,
      10             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12             :  * GNU General Public License for more details.
      13             :  *
      14             :  * You should have received a copy of the GNU General Public License
      15             :  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
      16             :  */
      17             : 
      18             : #include "precompiled.h"
      19             : 
      20             : #include "BoundingBoxOriented.h"
      21             : #include "maths/BoundingBoxAligned.h"
      22             : 
      23             : #include <float.h>
      24             : 
      25           1 : const CBoundingBoxOriented CBoundingBoxOriented::EMPTY = CBoundingBoxOriented();
      26             : 
      27           0 : CBoundingBoxOriented::CBoundingBoxOriented(const CBoundingBoxAligned& bound)
      28             : {
      29           0 :     if (bound.IsEmpty())
      30             :     {
      31           0 :         SetEmpty();
      32             :     }
      33             :     else
      34             :     {
      35           0 :         bound.GetCenter(m_Center);
      36             : 
      37             :         // the axes of an AABB are the world-space axes
      38           0 :         m_Basis[0].X = 1.f; m_Basis[0].Y = 0.f; m_Basis[0].Z = 0.f;
      39           0 :         m_Basis[1].X = 0.f; m_Basis[1].Y = 1.f; m_Basis[1].Z = 0.f;
      40           0 :         m_Basis[2].X = 0.f; m_Basis[2].Y = 0.f; m_Basis[2].Z = 1.f;
      41             : 
      42             :         // element-wise division by two to get half sizes (remember, [1] and [0] are the max and min coord points)
      43           0 :         m_HalfSizes = (bound[1] - bound[0]) * 0.5f;
      44             :     }
      45           0 : }
      46             : 
      47           2 : bool CBoundingBoxOriented::RayIntersect(const CVector3D& origin, const CVector3D& dir, float& tMin_out, float& tMax_out) const
      48             : {
      49             :     // See Real-Time Rendering, Third Edition, p. 743
      50           2 :     float tMin = -FLT_MAX;
      51           2 :     float tMax = FLT_MAX;
      52             : 
      53           2 :     CVector3D p = m_Center - origin;
      54             : 
      55           6 :     for (int i = 0; i < 3; ++i)
      56             :     {
      57             :         // test the ray for intersections with the slab whose normal vector is m_Basis[i]
      58           5 :         float e = m_Basis[i].Dot(p); // distance between the ray origin and the box center projected onto the slab normal
      59           5 :         float f = m_Basis[i].Dot(dir); // cosine of the angle between the slab normal and the ray direction
      60             : 
      61           5 :         if(fabsf(f) > 1e-10f)
      62             :         {
      63             :             // Determine the distances t1 and t2 from the origin of the ray to the points where it intersects
      64             :             // the slab. See docs/ray_intersect.pdf for why/how this works.
      65           4 :             float invF = 1.f/f;
      66           4 :             float t1 = (e + m_HalfSizes[i]) * invF;
      67           4 :             float t2 = (e - m_HalfSizes[i]) * invF;
      68             : 
      69             :             // make sure t1 <= t2, swap if necessary
      70           4 :             if (t1 > t2)
      71             :             {
      72           2 :                 float tmp = t1;
      73           2 :                 t1 = t2;
      74           2 :                 t2 = tmp;
      75             :             }
      76             : 
      77             :             // update the overall tMin and tMax if necessary
      78           4 :             if (t1 > tMin) tMin = t1;
      79           4 :             if (t2 < tMax) tMax = t2;
      80             : 
      81             :             // try to break out of the loop as fast as possible by checking for some conditions
      82           4 :             if (tMin > tMax) return false; // ray misses the box
      83           3 :             if (tMax < 0) return false; // box is behind the ray origin
      84             :         }
      85             :         else
      86             :         {
      87             :             // the ray is parallel to the slab currently being tested, or is as close to parallel
      88             :             // as makes no difference; return false if the ray is outside of the slab.
      89           1 :             if (e > m_HalfSizes[i] || -e > m_HalfSizes[i])
      90           0 :                 return false;
      91             :         }
      92             :     }
      93             : 
      94           1 :     tMin_out = tMin;
      95           1 :     tMax_out = tMax;
      96           1 :     return true;
      97           3 : }