将深度作为纹理从帧缓冲区渲染到显示窗口

Question

我是OpenGL的新手。我想使用帧缓冲区读取并保存渲染场景中的所有深度值。我设法将其设置为附加到深度组件的帧缓冲区。但是当我将深度纹理渲染到默认帧缓冲区（显示窗口）时，它只显示白色，即使我线性化了深度值（教程从https://learnopengl.com/开始）。当我在默认帧缓冲区片段着色器中从gl_FragCoord. z访问深度值时，我会得到一个深度图，并且绘图也可以，但是当将深度作为纹理从单独的帧缓冲区发送到默认时，深度图像是强烈的白色。

我为此编写的代码如下：

自定义帧缓冲区顶点和片段着色器

const char* vertexShaderFBO =
        "#version 330\n"
        "layout (location = 0)  in vec3 vp;"
        "uniform mat4 camera;"
        "uniform mat4 projection;"
        "void main() {"
        "  gl_Position = camera * projection * vec4(vp.x, vp.y, vp.z, 1.0);"
        "}";

const char* fragmentShaderFBO =
        "#version 330\n"
        "layout (location = 0) out float frag_depth;"
        "float near = 0.1;"
        "float far = 100;"
        "float LinearizeDepth(float depth)"
        "{"
        "    float z = depth * 2.0 - 1.0;"
        "   return (2.0 * near * far) / (far + near - z * (far - near));"
        "}"
        "void main() {"
        "  float linearDepth = LinearizeDepth(gl_FragCoord.z) / far;" // divided by far is just to visualize depth
        "  frag_depth = linearDepth ;"
        "}";

默认帧缓冲区顶点和片段着色器

const char* vertexShader =
        "#version 330\n"
        "layout (location = 0)  in vec3 vp;"
        "uniform mat4 camera;"
        "uniform mat4 projection;"
        "void main() {"
        "  gl_Position =  camera * projection * vec4(vp.x, vp.y, vp.z, 1.0);"
        "}";

const char* fragmentShader =
        "#version 330\n"
        "out vec4 frag_colour;"
        "uniform sampler2D depthSampler;"
        "in vec2 texCoords;"
        "void main() {"
        "  float depthVal = texture(depthSampler, texCoords).r;"
        "  frag_colour = vec4(vec3(depthVal), 1);"
        "}";

深度纹理

GLuint setDepthTexture()
{
    GLuint texture;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, SCREEN_SIZE.x, SCREEN_SIZE.y, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);

    return texture;
}

渲染文件

int renderOFF(Vertices* vertices, Faces* faces, Views* views)
{
    // initializaion
    ... 
    ...
    glEnable(GL_DEPTH_TEST); // enable depth buffer
    glDepthFunc(GL_LESS); // If pixel closer to camera then overwrite the existing pixel

    ...
    ...

    // create framebuffer shader
    GLuint shaderProgramFBO = createShader(vertexShaderFBO, fragmentShaderFBO);

    // create renderer shader
    GLuint shaderProgram = createShader(vertexShader, fragmentShader);

    //set texture
    GLuint depthTexture = setDepthTexture();

    // set framebuffer
    unsigned int fbo;
    glGenFramebuffers(1, &fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);

    // attach texture to framebuffer
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthTexture, 0);

    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
        std::cout << "Failed to bind framebuffer" << std::endl;
        return -1;
    }

     // Use no color attachment
    glDrawBuffer(GL_NONE);
    glReadBuffer(GL_NONE);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    glUseProgram(shaderProgram);
    glUniform1i(glGetUniformLocation(shaderProgram, "depthSampler"), 0);

    // set camera
    ...
    ...

    while(!glfwWindowShouldClose(glfWwindow))
    {
        // check OpenGL error
        GLenum err;
        while ((err = glGetError()) != GL_NO_ERROR) {
            std::cout << "OpenGL error: " << err << std::endl;
        }


        // bind to custom framebuffer
        glBindFramebuffer(GL_FRAMEBUFFER, fbo);

        glClearColor(0, 0, 0, 1); // clear screen to black
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glUseProgram(shaderProgramFBO);
        ...

        glEnable(GL_DEPTH_TEST);

        glBindVertexArray(vao);
        glDrawElements(GL_TRIANGLES, faces->size, GL_UNSIGNED_INT, 0);

        glBindFramebuffer(GL_FRAMEBUFFER, 0);

        // default framebuffer
        glClearColor(0, 0, 0, 1); // clear screen to black
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        processKeyBoardInput(glfWwindow);

        ...

        //glDisable(GL_DEPTH_TEST);
        glBindVertexArray(vao);
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, depthTexture);
        glDrawElements(GL_TRIANGLES, faces->size, GL_UNSIGNED_INT, 0);

        glfwSwapBuffers(glfWwindow);
        glfwPollEvents();

        sleep(1);
    }

    glDeleteFramebuffers(1, &fbo);
    glDeleteVertexArrays(1, &vao);
    glDeleteBuffers(1, &vbo);

    glfwTerminate();
    return 0;
}

Answer 1

片段着色器将范围[near，far]中的深度值指定给范围[0.0，1.0]中的颜色值。如果所有几何体都位于接近0.0的区域中，则渲染将几乎显示为黑色，因为0.1渲染为黑色，100渲染为白色。将观察体积（视锥台）的近平面和远平面移动到尽可能靠近几何体的位置，以利用0.0到1.0之间的整个范围。

当近平面接近0时，您的片段着色器将正常工作。随着近平面变大，您应该使用：

float linearDepth=linearedeph（gl_FragCoord.z）/far

float linearDepth = (LinearizeDepth(gl_FragCoord.z) - near) / (far - near);