OpenGL 帧缓冲区的应用

末蓝、 2023-06-08 05:00 5阅读 0赞

有两个渲染器，分别为program1 和 program2。

program1的渲染到窗口。

glViewport(0, 0, 512, 512);
     glClearBufferfv(GL_COLOR, 0, sb7::color::Green);  //背景色
     glClearBufferfi(GL_DEPTH_STENCIL, 0, 1.0f, 0);
    
     glUseProgram(program1);
     glUniformMatrix4fv(proj_location, 1, GL_FALSE, proj_matrix); //投影矩阵
     glUniformMatrix4fv(mv_location, 1, GL_FALSE, mv_matrix);     //模型视图矩阵
     glDrawArrays(GL_TRIANGLES, 0, 36);

渲染结果如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpeWF6aGVuMjAxMQ_size_16_color_FFFFFF_t_70][]

现在将program1渲染到纹理，program2使用该纹理并渲染到窗口。

首先，创建帧缓冲区对象，并绑定纹理。

glGenFramebuffers(1, &fbo);
        glBindFramebuffer(GL_FRAMEBUFFER, fbo);
    
        glGenTextures(1, &color_texture);
        glBindTexture(GL_TEXTURE_2D, color_texture);
        glTexStorage2D(GL_TEXTURE_2D, 9, GL_RGBA8, 512, 512);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    
        glGenTextures(1, &depth_texture);
        glBindTexture(GL_TEXTURE_2D, depth_texture);
        glTexStorage2D(GL_TEXTURE_2D, 9, GL_DEPTH_COMPONENT32F, 512, 512);
    
        glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, color_texture, 0);
        glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depth_texture, 0);

其次，设置缓冲区映射，每个缓冲区指定颜色绑定。

static const GLenum draw_buffers[] = { GL_COLOR_ATTACHMENT0 };
     glDrawBuffers(1, draw_buffers);

然后，program1渲染到纹理。

//program1渲染到纹理
        glBindFramebuffer(GL_FRAMEBUFFER, fbo);    //启用帧缓冲区，其绑定了纹理
        glViewport(0, 0, 512, 512);
        glClearBufferfv(GL_COLOR, 0, sb7::color::Green);
        glClearBufferfi(GL_DEPTH_STENCIL, 0, 1.0f, 0);
        glUseProgram(program1);
        glUniformMatrix4fv(proj_location, 1, GL_FALSE, proj_matrix);
        glUniformMatrix4fv(mv_location, 1, GL_FALSE, mv_matrix);
        glDrawArrays(GL_TRIANGLES, 0, 36);
        glBindFramebuffer(GL_FRAMEBUFFER, 0);    //关闭帧缓冲区

program2使用上述纹理渲染到窗口。

//program2渲染到窗口
        glViewport(0, 0, info.windowWidth, info.windowHeight);
        glClearBufferfv(GL_COLOR, 0, blue);
        glClearBufferfv(GL_DEPTH, 0, &one);
        glBindTexture(GL_TEXTURE_2D, color_texture);   //绑定program1生成的纹理
        glUseProgram(program2);
        glUniformMatrix4fv(proj_location2, 1, GL_FALSE, proj_matrix);
        glUniformMatrix4fv(mv_location2, 1, GL_FALSE, mv_matrix);
        glDrawArrays(GL_TRIANGLES, 0, 36);
        glBindTexture(GL_TEXTURE_2D, 0);

渲染结果如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpeWF6aGVuMjAxMQ_size_16_color_FFFFFF_t_70 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpeWF6aGVuMjAxMQ_size_16_color_FFFFFF_t_70]: /images/20230531/7de2d426378e47128f09f3976a862bc2.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpeWF6aGVuMjAxMQ_size_16_color_FFFFFF_t_70 1]: /images/20230531/e0ae986768494e54aca0ae1905884a4b.png