[原]OpenGL基础教程（五）缓冲区数据更新方式

1、glBufferSubData 适用于相同数据类型

void SetPositionY(float y)
{
   vector<Vector3<float>>::iterator ver3;
   for(ver3 = vertices.begin();ver3!=vertices.end();ver3++)
   {
       ver3->y +=y;
   }
   glBindBuffer(GL_ARRAY_BUFFER,posHandler);
    glBufferSubData(GL_ARRAY_BUFFER,0,vertices.size() * sizeof(vertices[0]),&vertices[0]);
   glBindBuffer(GL_ARRAY_BUFFER,0);
   display( );
}

2、glMapBuffer 适用于对缓冲区大部分数据更新

void SetPositionY(float y)
{
　　....................
   glBindBuffer(GL_ARRAY_BUFFER,posHandler);
   void *buf = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
   memcpy(buf, &vertices[0], sizeof(vertices[0])*vertices.size());
   glUnmapBuffer(GL_ARRAY_BUFFER);
   glBindBuffer(GL_ARRAY_BUFFER,0);
    ..............
}

以上两种方式效果图：

3、glMapBufferRange 适用于大缓冲区里面小部分数据更新

void SetPositionY(float y)
{
　　.............
   glBindBuffer(GL_ARRAY_BUFFER,posHandler);
    void *buf = glMapBufferRange(GL_ARRAY_BUFFER, 0, sizeof(vertices[0])*50, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT | GL_MAP_UNSYNCHRONIZED_BIT);
    memcpy(buf, &vertices[0], sizeof(vertices[0])*50);
   glUnmapBuffer(GL_ARRAY_BUFFER);
   glBindBuffer(GL_ARRAY_BUFFER,0);
    ..............................
}

因为所有字是一个数组更新前50个顶点所以有点乱

特别说明：更新完数据一定要调从绘函数也就是glutDisplayFunc绑定的回调函数，本文为display( );

参考：http://iqnix.blog.163.com/blog/static/21721982014228115223718/

　　 http://www.zwqxin.com/archives/opengl/learn-vbo.html