glGenBuffers(1, &pbo);
glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, pbo);
glBufferData(GL_PIXEL_PACK_BUFFER_ARB, global_flags.width * global_flags.height * 4, NULL, GL_STREAM_READ);
glGenBuffers(1, &pbo);
glBindBuffer(GL_PIXEL_PACK_BUFFER_ARB, pbo);
glBufferData(GL_PIXEL_PACK_BUFFER_ARB, global_flags.width * global_flags.height * 4, NULL, GL_STREAM_READ);