Developer Documentation
MeshNode2.cc
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49 
50 #include <ACG/GL/acg_glew.hh>
51 #include "MeshNode2T.hh"
52 
53 namespace ACG {
54 namespace SceneGraph {
55 
56 MeshNodeBase::MeshNodeBase(BaseNode* _parent, std::string _name) :
57  BaseNode(_parent, _name),
58  drawMeshBase_(0),
59  polyEdgeBuf_(0),
60  polyEdgeBufSize_(0),
61  polyEdgeBufTex_(0) {
62 }
63 
64 void MeshNodeBase::supplyDrawMesh(DrawMeshBase *drawMeshBase) {
65  /*
66  * We take the luxury of checking these conditions even in release
67  * mode as this method is rarely called.
68  */
69  if (drawMeshBase_)
70  throw std::runtime_error("MeshNodeBase::supplyDrawMesh called "
71  "more than once.");
72  if (!drawMeshBase)
73  throw std::runtime_error("MeshNodeBase::supplyDrawMesh called "
74  "with NULL parameter.");
75 
76  drawMeshBase_ = drawMeshBase;
77 }
78 
79 void MeshNodeBase::updatePolyEdgeBuf()
80 {
81 
82 #ifdef GL_ARB_texture_buffer_object
83  // drawMeshBase_ must have been supplied.
84  assert(drawMeshBase_);
85 
86  MeshCompiler * const mc = drawMeshBase_->getMeshCompiler();
87  if (mc && !mc->isTriangleMesh())
88  {
89  // create/update the poly-edge buffer
90  if (!polyEdgeBuf_)
91  glGenBuffers(1, &polyEdgeBuf_);
92 
93  const int nTris = mc->getNumTriangles();
94 
95  const int newBufSize = (nTris/2+1);
96 
97  if (polyEdgeBufSize_ != newBufSize)
98  {
99  glBindBuffer(GL_TEXTURE_BUFFER, polyEdgeBuf_);
100 
101  // The poly-edge buffer is a texture buffer that stores one byte for each triangle, which encodes triangle edge properties.
102  // An inner edge is an edge that was added during the triangulation of a n-poly,
103  // whereas outer edges are edges that already exist in the input mesh object.
104  // This information is used in the wireframe/hiddenline geometry shader to identify edges, which should not be rendered.
105  // Buffer storage:
106  // each triangle uses 3 bits to mark edges as visible or hidden
107  // outer edge -> bit = 1 (visible)
108  // inner edge -> bit = 0 (hidden)
109  // each byte can store edges for two triangles and the remaining 2 bits are left unused
110 
111  polyEdgeBufSize_ = newBufSize;
112  unsigned char* polyEdgeBufData = new unsigned char[newBufSize];
113 
114  // set zero
115  memset(polyEdgeBufData, 0, newBufSize);
116 
117  // build buffer
118  for (int i = 0; i < nTris; ++i)
119  {
120  int byteidx = i>>1;
121  int bitidx = (i&1) * 3;
122 
123  for (int k = 0; k < 3; ++k)
124  if (mc->isFaceEdge(i, k))
125  polyEdgeBufData[byteidx] += 1 << (k + bitidx);
126  }
127 
128  glBufferData(GL_TEXTURE_BUFFER, polyEdgeBufSize_, polyEdgeBufData, GL_STATIC_DRAW);
129 
130 
131  delete [] polyEdgeBufData;
132  polyEdgeBufData = 0;
133 
134  // create texture object for the texture buffer
135 
136  if (!polyEdgeBufTex_)
137  {
138  glGenTextures(1, &polyEdgeBufTex_);
139 
140  glActiveTexture(GL_TEXTURE0);
141  glBindTexture(GL_TEXTURE_BUFFER, polyEdgeBufTex_);
142  glTexBuffer(GL_TEXTURE_BUFFER, GL_R8UI, polyEdgeBuf_);
143 
144  glBindTexture(GL_TEXTURE_2D, 0);
145  }
146 
148  }
149  }
150 #endif
151 }
152 
153 
154 } /* namespace SceneGraph */
155 } /* namespace ACG */
Namespace providing different geometric functions concerning angles.
Definition: DBSCANT.cc:51
void glCheckErrors()
Definition: GLError.hh:105