text: ﻿/********************************************************************************
  * ReactPhysics3D physics library, http://www.reactphysics3d.com                 *
  * Copyright (c) 2010-2019 Daniel Chappuis                                       *
  *********************************************************************************
  *                                                                               *
  * This software is provided 'as-is', without any express or implied warranty.   *
  * In no event will the authors be held liable for any damages arising from the  *
  * use of this software.                                                         *
  *                                                                               *
  * Permission is granted to anyone to use this software for any purpose,         *
  * including commercial applications, and to alter it and redistribute it        *
  * freely, subject to the following restrictions:                                *
  *                                                                               *
  * 1. The origin of this software must not be misrepresented; you must not claim *
  *    that you wrote the original software. If you use this software in a        *
  *    product, an acknowledgment in the product documentation would be           *
  *    appreciated but is not required.                                           *
  *                                                                               *
  * 2. Altered source versions must be plainly marked as such, and must not be    *
  *    misrepresented as being the original software.                             *
  *                                                                               *
  * 3. This notice may not be removed or altered from any source distribution.    *
  *                                                                               *
  ********************************************************************************/
  
  // Libraries
  #include "BoxShape.h"
  #include "collision/ProxyShape.h"
  #include "configuration.h"
  #include "memory/MemoryManager.h"
  #include "collision/RaycastInfo.h"
  #include <cassert>
  
  using namespace reactphysics3d;
  
  // Constructor
  /**
   * @param extent The vector with the three extents of the box (in meters)
   */
  BoxShape::BoxShape(const Vector3& extent)
           : ConvexPolyhedronShape(CollisionShapeName::BOX), mExtent(extent),
             mHalfEdgeStructure(MemoryManager::getBaseAllocator(), 6, 8, 24) {
  
      assert(extent.x > decimal(0.0));
      assert(extent.y > decimal(0.0));
      assert(extent.z > decimal(0.0));
  
      // Vertices
      mHalfEdgeStructure.addVertex(0);
      mHalfEdgeStructure.addVertex(1);
      mHalfEdgeStructure.addVertex(2);
      mHalfEdgeStructure.addVertex(3);
      mHalfEdgeStructure.addVertex(4);
      mHalfEdgeStructure.addVertex(5);
      mHalfEdgeStructure.addVertex(6);
      mHalfEdgeStructure.addVertex(7);
  
      MemoryAllocator& allocator = MemoryManager::getBaseAllocator();
  
      // Faces
      List<uint> face0(allocator, 4);
      face0.add(0); face0.add(1); face0.add(2); face0.add(3);
      List<uint> face1(allocator, 4);
      face1.add(1); face1.add(5); face1.add(6); face1.add(2);
      List<uint> face2(allocator, 4);
      face2.add(4); face2.add(7); face2.add(6); face2.add(5);
      List<uint> face3(allocator, 4);
      face3.add(4); face3.add(0); face3.add(3); face3.add(7);
      List<uint> face4(allocator, 4);
      face4.add(4); face4.add(5); face4.add(1); face4.add(0);
      List<uint> face5(allocator, 4);
      face5.add(2); face5.add(6); face5.add(7); face5.add(3);
  
      mHalfEdgeStructure.addFace(face0);
      mHalfEdgeStructure.addFace(face1);
      mHalfEdgeStructure.addFace(face2);
      mHalfEdgeStructure.addFace(face3);
      mHalfEdgeStructure.addFace(face4);
      mHalfEdgeStructure.addFace(face5);
  
  	mHalfEdgeStructure.init();
  }
  
  // Return the local inertia tensor of the collision shape
  /**
   * @param[out] tensor The 3x3 inertia tensor matrix of the shape in local-space
   *                    coordinates
   * @param mass Mass to use to compute the inertia tensor of the collision shape
   */
  void BoxShape::computeLocalInertiaTensor(Matrix3x3& tensor, decimal mass) const {
      decimal factor = (decimal(1.0) / decimal(3.0)) * mass;
      decimal xSquare = mExtent.x * mExtent.x;
      decimal ySquare = mExtent.y * mExtent.y;
      decimal zSquare = mExtent.z * mExtent.z;
      tensor.setAllValues(factor * (ySquare + zSquare), 0.0, 0.0,
                          0.0, factor * (xSquare + zSquare), 0.0,
                          0.0, 0.0, factor * (xSquare + ySquare));
  }
  
  // Raycast method with feedback information
  bool BoxShape::raycast(const Ray& ray, RaycastInfo& raycastInfo, ProxyShape* proxyShape, MemoryAllocator& allocator) const {
  
      Vector3 rayDirection = ray.point2 - ray.point1;
      decimal tMin = DECIMAL_SMALLEST;
      decimal tMax = DECIMAL_LARGEST;
      Vector3 normalDirection(decimal(0), decimal(0), decimal(0));
      Vector3 currentNormal;
  
      // For each of the three slabs
      for (int i=0; i<3; i++) {
  
          // If ray is parallel to the slab
          if (rpAbs(rayDirection[i]) < MACHINE_EPSILON) {
  
              // If the ray's origin is not inside the slab, there is no hit
              if (ray.point1[i] > mExtent[i] || ray.point1[i] < -mExtent[i]) return false;
          }
          else {
  
              // Compute the intersection of the ray with the near and far plane of the slab
              decimal oneOverD = decimal(1.0) / rayDirection[i];
              decimal t1 = (-mExtent[i] - ray.point1[i]) * oneOverD;
              decimal t2 = (mExtent[i] - ray.point1[i]) * oneOverD;
              currentNormal[0] = (i == 0) ? -mExtent[i] : decimal(0.0);
              currentNormal[1] = (i == 1) ? -mExtent[i] : decimal(0.0);
              currentNormal[2] = (i == 2) ? -mExtent[i] : decimal(0.0);
  
              // Swap t1 and t2 if need so that t1 is intersection with near plane and
              // t2 with far plane
              if (t1 > t2) {
                  std::swap(t1, t2);
                  currentNormal = -currentNormal;
              }
  
              // Compute the intersection of the of slab intersection interval with previous slabs
              if (t1 > tMin) {
                  tMin = t1;
                  normalDirection = currentNormal;
              }
              tMax = std::min(tMax, t2);
  
              // If tMin is larger than the maximum raycasting fraction, we return no hit
              if (tMin > ray.maxFraction) return false;
  
              // If the slabs intersection is empty, there is no hit
              if (tMin > tMax) return false;
          }
      }
  
      // If tMin is negative, we return no hit
      if (tMin < decimal(0.0) || tMin > ray.maxFraction) return false;
  
      // The ray intersects the three slabs, we compute the hit point
      Vector3 localHitPoint = ray.point1 + tMin * rayDirection;
  
      raycastInfo.body = proxyShape->getBody();
      raycastInfo.proxyShape = proxyShape;
      raycastInfo.hitFraction = tMin;
      raycastInfo.worldPoint = localHitPoint;
      raycastInfo.worldNormal = normalDirection;
  
      return true;
  }
  