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有没有人有 PBO（像素缓冲区对象）+ SDL2.0（简单 DirectMedia 层）+ OpenGL 的工作示例？

原因是使用 GLGetPixels 获得异步 GPU -> CPU 下载，从而获得性能提升。

这是我的尝试。use_pbo = false 或 true 根本没有测量差异。而且我之前在同一台机器上使用过带有 GLUT 的 PBO，所以我知道我的硬件支持它。

我看了很多http://www.songho.ca/opengl/gl_pbo.html教程，但没有看到我做错了什么。

bool use_pbo = true; //remember to wait a bit for fps to pick up speed

if(SDL_Init(SDL_INIT_EVENTS) != 0) throw "SDL_Init";

SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

sdl_window = SDL_CreateWindow("", 10, 20, window_width, window_height, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);

sdl_gl_context = SDL_GL_CreateContext(sdl_window);
SDL_GL_MakeCurrent(sdl_window, sdl_gl_context);

vertical_sync(false);

{
    glGenBuffers(2, pbos);
    glBindBuffer(GL_PIXEL_PACK_BUFFER, pbos[0]);
    glBufferData(GL_PIXEL_PACK_BUFFER, pbo_width*pbo_height*4, 0, GL_STREAM_READ);

    glBindBuffer(GL_PIXEL_PACK_BUFFER, pbos[1]);
    glBufferData(GL_PIXEL_PACK_BUFFER, pbo_width*pbo_height*4, 0, GL_STREAM_READ);

    glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
}

//render to default frame buffer
{
    glDrawBuffer(GL_BACK);

    glClearColor(0.1, 0.2, 0.3, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

    glUseProgram(simple_shader);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, transparent_texture);

    glBegin(GL_TRIANGLE_STRIP);
    //textcoord, color, position
    glVertexAttrib2f(2, 0, 1); glVertexAttrib4f(1, 1, 0, 0, 1); glVertexAttrib2f(0, -1, -1); //bottom left
    glVertexAttrib2f(2, 1, 1); glVertexAttrib4f(1, 0, 1, 0, 1); glVertexAttrib2f(0, +1, -1); //bottom right
    glVertexAttrib2f(2, 0, 0); glVertexAttrib4f(1, 0, 0, 1, 1); glVertexAttrib2f(0, -1, +1); //top left
    glVertexAttrib2f(2, 1, 0); glVertexAttrib4f(1, 1, 1, 0, 1); glVertexAttrib2f(0, +1, +1); //top right
    glEnd();

    glBindTexture(GL_TEXTURE_2D, 0);

    glUseProgram(0);

    glDisable(GL_BLEND);

    while(true)
    {
        if(use_pbo)
        {
            glBindBuffer(GL_PIXEL_PACK_BUFFER, pbos[1]);
            GLvoid* map_buffer_data = glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);

            if(map_buffer_data)
            {
                //glRasterPos2i(-1, -1); //default, left bottom
                glRasterPos2i(0, -1);
                glDrawPixels(pbo_width, pbo_height, GL_BGRA, GL_UNSIGNED_BYTE, map_buffer_data);
                glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
            }

            glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
        }
        else
        {       
            glRasterPos2i(0, -1); //right bottom
            glDrawPixels(pbo_width, pbo_height, GL_BGRA, GL_UNSIGNED_BYTE, t.c);
        }
    }
}

SDL_GL_SwapWindow(sdl_window);

//cycle buffers
{
    GLuint t = pbos[1];
    pbos[1] = pbos[0];
    pbos[0] = t;
}
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1 回答 1

0

尝试将 PBO 绑定到您的纹理

GL_PIXEL_UNPACK_BUFFER 用于将像素数据传递到 OpenGL GL_PIXEL_PACK_BUFFER 用于从 OpenGL检索像素数据

你也应该用glTexImage2D定义纹理图像

如果在指定纹理图像时将非零命名缓冲区对象绑定到 GL_PIXEL_UNPACK_BUFFER 目标（请参阅 glBindBuffer），则数据将被视为缓冲区对象数据存储中的字节偏移量。

于 2016-02-26T14:51:38.757 回答