opengl-vao-vbo

最新推荐文章于 2025-10-29 10:32:49 发布

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本文介绍了一个使用OpenGL ES进行三角形绘制的具体示例，包括定义顶点结构、设置顶点缓冲区对象(VBO)及索引缓冲区对象(IBO)，并详细展示了如何通过顶点着色器和片段着色器来处理顶点坐标、法线及纹理坐标。

 struct MyVertex
  {
    float x, y, z;        //Vertex
    float nx, ny, nz;     //Normal
    float s0, t0;         //Texcoord0
  };
  
  MyVertex pvertex[3];
  //VERTEX 0
  pvertex[0].x = 0.0;
  pvertex[0].y = 0.0;
  pvertex[0].z = 0.0;
  pvertex[0].nx = 0.0;
  pvertex[0].ny = 0.0;
  pvertex[0].nz = 1.0;
  pvertex[0].s0 = 0.0;
  pvertex[0].t0 = 0.0;
  //VERTEX 1
  pvertex[1].x = 1.0;
  pvertex[1].y = 0.0;
  pvertex[1].z = 0.0;
  pvertex[1].nx = 0.0;
  pvertex[1].ny = 0.0;
  pvertex[1].nz = 1.0;
  pvertex[1].s0 = 1.0;
  pvertex[1].t0 = 0.0;
  //VERTEX 2
  pvertex[2].x = 0.0;
  pvertex[2].y = 1.0;
  pvertex[2].z = 0.0;
  pvertex[2].nx = 0.0;
  pvertex[2].ny = 0.0;
  pvertex[2].nz = 1.0;
  pvertex[2].s0 = 0.0;
  pvertex[2].t0 = 1.0;
  
  glGenBuffers(1, VertexVBOID);
  glBindBuffer(GL_ARRAY_BUFFER, VertexVBOID);
  glBufferData(GL_ARRAY_BUFFER, sizeof(MyVertex)*3, &pvertex[0].x, GL_STATIC_DRAW);
  
  ushort pindices[3];
  pindices[0] = 0;
  pindices[1] = 1;
  pindices[2] = 2;
  
  glGenBuffers(1, &IndexVBOID);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexVBOID);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(ushort)*3, pindices, GL_STATIC_DRAW);
  
  //Define this somewhere in your header file
  define BUFFER_OFFSET(i) ((char *)NULL + (i))
  
  glBindBuffer(GL_ARRAY_BUFFER, VertexVBOID);
  glEnableVertexAttribArray(0);    //We like submitting vertices on stream 0 for no special reason
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(MyVertex), BUFFER_OFFSET(0));   //The starting point of the VBO, for the vertices
  glEnableVertexAttribArray(1);    //We like submitting normals on stream 1 for no special reason
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(MyVertex), BUFFER_OFFSET(12));     //The starting point of normals, 12 bytes away
  glEnableVertexAttribArray(2);    //We like submitting texcoords on stream 2 for no special reason
  glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(MyVertex), BUFFER_OFFSET(24));   //The starting point of texcoords, 24 bytes away
  
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexVBOID);
  //To render, we can either use glDrawElements or glDrawRangeElements
  //The is the number of indices. 3 indices needed to make a single triangle
  glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0));   //The starting point of the IBO
  //0 and 3 are the first and last vertices
  //glDrawRangeElements(GL_TRIANGLES, 0, 3, 3, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0));   //The starting point of the IBO
  //glDrawRangeElements may or may not give a performance advantage over glDrawElements