立方体贴图/帧缓冲问题

Question

所以...我正在尝试为 BRDF 着色器过滤环境贴图，如下所述：https://learnopengl.com/PBR/IBL/Specular-IBL。但是，我无法正确存储过滤后的结果（加载时，我得到一个充满伪影的黑色纹理。）

我认为它一定与帧缓冲区有关，因为 glCheckFramebufferStatus() 在 LOD/sides 循环上一直返回 0，但我花了几个小时试图理解为什么......我看不到问题。 glGetError() 返回 0，我确保在循环开始之前生成帧缓冲区/渲染/缓冲区，此时一切似乎都完成了。程序的其余部分运行良好，编译我正在使用的着色器没有错误。

我对openGL很陌生，有什么明显的我遗漏的吗？我假设问题必须在本节中......但它看起来应该有效吗？会不会是我在其他地方做错了什么？

这是代码：

if (cubeMapGenerated == false){
    //Frame Buffer:
    glGenFramebuffers(1, &frameBuffer);
    glGenRenderbuffers(1, &renderBuffer);
    glGenTextures(1, &genCubeMap);

    glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
    glBindTexture(GL_TEXTURE_CUBE_MAP, genCubeMap);

    for (unsigned int i = 0; i < 6; ++i)
    {glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGBA16F, 128, 128, 0, GL_RGB, GL_FLOAT, nullptr);}
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); //params
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glGenerateMipmap(GL_TEXTURE_CUBE_MAP); //generate mipmaps

    glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width_, height_);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer);

    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
       std::cout << "Framebuffer is not complete at gen. Staus: " << glCheckFramebufferStatus(GL_FRAMEBUFFER) << std::endl;

    GLuint projection_location, view_location, model_location, normal_matrix_location,
        specular_map_location, roughness_location;

    cubeMapGen_program_->bind(); //bind irradiance sahder
    projection_location = cubeMapGen_program_->uniformLocation("projection");
    view_location = cubeMapGen_program_->uniformLocation("view");
    model_location = cubeMapGen_program_->uniformLocation("model");
    normal_matrix_location = cubeMapGen_program_->uniformLocation("normal_matrix");
    specular_map_location = cubeMapGen_program_->uniformLocation("specular_map");
    roughness_location =brdf_program_->uniformLocation("roughness");

    glUniformMatrix4fv(projection_location, 1, GL_FALSE, e_captureProjection.data());
    glUniformMatrix4fv(model_location, 1, GL_FALSE, model.data());
    glUniformMatrix3fv(normal_matrix_location, 1, GL_FALSE, normal.data());

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_CUBE_MAP, specular_map_);
    glUniform1i(specular_map_location, 0);

    for (unsigned int mip = 0; mip < maxMipLevels; ++mip){//render each mip
        // resize framebuffer according to mip-level size.
        unsigned int mipWidth  = 128 * std::pow(0.5, mip);
        unsigned int mipHeight = 128 * std::pow(0.5, mip);
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, mipWidth, mipHeight);
        std::cout << "width: " << mipWidth << " height: " << mipHeight << std::endl;

        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer);
        glViewport(0, 0, mipWidth, mipHeight);

        float mproughness = (float) mip / (float)(maxMipLevels - 1);
        glUniform1f (roughness_location, mproughness);

        for (unsigned int i = 0; i < 6; ++i)//render each side
        {
            glUniformMatrix4fv(view_location, 1, GL_FALSE, e_captureViews[i].data());
            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, genCubeMap, mip);

            if(i == 0 && glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            {std::cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete! Map: " << mip << std::endl;}

            glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            glBegin(GL_TRIANGLES);
            glVertex3f(2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, 2, 2); //Right
            glVertex3f(2, -2, -2); glVertex3f(2, 2, 2); glVertex3f(2, 2, -2);
            glVertex3f(-2, -2, -2); glVertex3f(-2, 2, 2); glVertex3f(-2, -2, 2); //Left
            glVertex3f(-2, -2, -2); glVertex3f(-2, 2, -2); glVertex3f(-2, 2, 2);
            glVertex3f(-2, -2, 2); glVertex3f(-2, 2, 2); glVertex3f(2, 2, 2); //Front
            glVertex3f(-2, -2, 2); glVertex3f(2, 2, 2); glVertex3f(2, -2, 2);
            glVertex3f(-2, -2, -2); glVertex3f(2, 2, -2); glVertex3f(-2, 2, -2); //Back
            glVertex3f(-2, -2, -2); glVertex3f(2, -2, -2); glVertex3f(2, 2, -2);
            glVertex3f(-2, 2, -2); glVertex3f(2, 2, -2); glVertex3f(2, 2, 2);   //Top
            glVertex3f(-2, 2, -2); glVertex3f(2, 2, 2); glVertex3f(-2, 2, 2);
            glVertex3f(-2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, -2, -2); //Bottom
            glVertex3f(-2, -2, -2); glVertex3f(-2, -2, 2); glVertex3f(2, -2, 2);
        }
    //std::cout << glGetError() << ", " << glCheckFramebufferStatus(GL_FRAMEBUFFER) << std::endl;
    }
    std::cout<<"New pre filtered map generated"<<std::endl;
    cubeMapGenerated = true;
    }//cubemapgen
    glEnd();

Answer 1

我建议阅读Vertex Specification 并使用Vertex Array Objects 最先进的方式进行绘图。

但是，如果您将对象绘制成已弃用的Fixed Function Pipeline 样式，则通过在glBegin/glEnd 对之间包含一系列顶点坐标来绘制几何对象。

您必须在glEnd 之前完成绘图序列，然后才能更改或操作帧缓冲区。

将glEnd 指令移到内部循环中，您的代码应该可以工作

for (unsigned int mip = 0; mip < maxMipLevels; ++mip)
{

    .....

    for (unsigned int i = 0; i < 6; ++i)//render each side
    {
         glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, genCubeMap, mip);

         glBegin(GL_TRIANGLES);
         glVertex3f(2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, 2, 2);

         .....

         glVertex3f(-2, -2, -2); glVertex3f(-2, -2, 2); glVertex3f(2, -2, 2);
         glEnd(); // <---- "end" the draw sequence 
    }
}

见OpenGL 3.0 API Specification; 2.6.3 GL Commands within Begin/End; page 24
或OpenGL 4.6 API Compatibility Profile Specification; 10.7.5 Commands Allowed Between Begin and End; page 433:

在任何 Begin/End 对中唯一允许的 GL 命令是用于指定顶点坐标、顶点颜色、法线坐标、纹理坐标、通用顶点属性和雾坐标的命令...