Code/CryEngine/Cry3DEngine/PolygonClipContext.cpp

   1 // Copyright 2001-2018 Crytek GmbH / Crytek Group. All rights reserved.
   2
   3 // -------------------------------------------------------------------------
   4 //  File name:   PolygonClipContext.cpp
   5 //  Created:
   6 //  Description:
   7 // -------------------------------------------------------------------------
   8 //  History:
   9 //
  10 ////////////////////////////////////////////////////////////////////////////
  11
  12 #include "StdAfx.h"
  13 #include "PolygonClipContext.h"
  14
  15 CPolygonClipContext::CPolygonClipContext()
  16 {
  17 }
  18
  19 void CPolygonClipContext::Reset()
  20 {
  21         stl::free_container(m_lstPolygonA);
  22         stl::free_container(m_lstPolygonB);
  23 }
  24
  25 int CPolygonClipContext::ClipEdge(const Vec3& v1, const Vec3& v2, const Plane& ClipPlane, Vec3& vRes1, Vec3& vRes2)
  26 {
  27         float d1 = -ClipPlane.DistFromPlane(v1);
  28         float d2 = -ClipPlane.DistFromPlane(v2);
  29         if (d1 < 0 && d2 < 0)
  30                 return 0; // all clipped = do not add any vertices
  31
  32         if (d1 >= 0 && d2 >= 0)
  33         {
  34                 vRes1 = v2;
  35                 return 1; // both not clipped - add second vertex
  36         }
  37
  38         // calculate new vertex
  39         Vec3 vIntersectionPoint = v1 + (v2 - v1) * (abs(d1) / (abs(d2) + abs(d1)));
  40
  41 #ifdef _DEBUG
  42         float fNewDist = -ClipPlane.DistFromPlane(vIntersectionPoint);
  43         assert(abs(fNewDist) < 0.01f);
  44 #endif
  45
  46         if (d1 >= 0 && d2 < 0)
  47         {
  48                 // from vis to no vis
  49                 vRes1 = vIntersectionPoint;
  50                 return 1;
  51         }
  52         else if (d1 < 0 && d2 >= 0)
  53         {
  54                 // from not vis to vis
  55                 vRes1 = vIntersectionPoint;
  56                 vRes2 = v2;
  57                 return 2;
  58         }
  59
  60         assert(0);
  61         return 0;
  62 }
  63
  64 void CPolygonClipContext::ClipPolygon(PodArray<Vec3>& PolygonOut, const PodArray<Vec3>& pPolygon, const Plane& ClipPlane)
  65 {
  66         PolygonOut.Clear();
  67         // clip edges, make list of new vertices
  68         for (int i = 0; i < pPolygon.Count(); i++)
  69         {
  70                 Vec3 vNewVert1(0, 0, 0), vNewVert2(0, 0, 0);
  71                 if (int nNewVertNum = ClipEdge(pPolygon.GetAt(i), pPolygon.GetAt((i + 1) % pPolygon.Count()), ClipPlane, vNewVert1, vNewVert2))
  72                 {
  73                         PolygonOut.Add(vNewVert1);
  74                         if (nNewVertNum > 1)
  75                                 PolygonOut.Add(vNewVert2);
  76                 }
  77         }
  78
  79         // check result
  80 #if defined(USE_CRY_ASSERT)
  81         for (int i = 0; i < PolygonOut.Count(); i++)
  82         {
  83                 float d1 = -ClipPlane.DistFromPlane(PolygonOut.GetAt(i));
  84                 assert(d1 >= -0.01f);
  85         }
  86 #endif
  87
  88         assert(PolygonOut.Count() == 0 || PolygonOut.Count() >= 3);
  89 }
  90
  91 const PodArray<Vec3>& CPolygonClipContext::Clip(const PodArray<Vec3>& poly, const Plane* planes, size_t numPlanes)
  92 {
  93         m_lstPolygonA.Clear();
  94         m_lstPolygonB.Clear();
  95
  96         m_lstPolygonA.AddList(poly);
  97
  98         PodArray<Vec3>* src = &m_lstPolygonA, * dst = &m_lstPolygonB;
  99
 100         for (size_t i = 0; i < numPlanes && src->Count() >= 3; std::swap(src, dst), i++)
 101                 ClipPolygon(*dst, *src, planes[i]);
 102
 103         return *src;
 104 }
 105
 106 const PodArray<Vec3>& CPolygonClipContext::Clip(const Vec3& a, const Vec3& b, const Vec3& c, const Plane* planes, size_t numPlanes)
 107 {
 108         m_lstPolygonA.Clear();
 109         m_lstPolygonB.Clear();
 110
 111         m_lstPolygonA.Add(a);
 112         m_lstPolygonA.Add(b);
 113         m_lstPolygonA.Add(c);
 114
 115         PodArray<Vec3>* src = &m_lstPolygonA, * dst = &m_lstPolygonB;
 116
 117         for (size_t i = 0; i < numPlanes && src->Count() >= 3; std::swap(src, dst), i++)
 118                 ClipPolygon(*dst, *src, planes[i]);
 119
 120         return *src;
 121 }
 122
 123 void CPolygonClipContext::GetMemoryUsage(ICrySizer* pSizer) const
 124 {
 125         pSizer->AddObject(m_lstPolygonA);
 126         pSizer->AddObject(m_lstPolygonB);
 127 }