OpenGL渲染到纹理（到屏幕）空白

Question

我在屏幕上绘制了很多点，并且试图将它们渲染到纹理以进行后期处理，然后再将纹理渲染回屏幕。 目前，我正试图通过并获得纹理渲染，但似乎没有渲染任何内容。

我的片段着色器可以正常工作（不渲染到纹理-在mEllipseTextureProgram中使用了波纹管），而我所做的唯一更改是包括了

out vec3 color;

渲染到纹理本身（显然更改为color =而不是gl_FragColor =）。 下面引用的第二个程序（mScreenProgram）如下：

顶点着色器：

    #version 330 compatibility
    in vec2 vUV;

    out vec2 UV;

    void main()
    {
        gl_Position = gl_Vertex;
        UV = vUV;
    }

片段着色器：

    #version 330 core

    in vec2 UV;

    out vec3 color;

    uniform sampler2D renderedTexture;

    void main(){
        color = texture( renderedTexture, UV ).xyz; 
    }

设置我的纹理渲染这样的东西 ：

    glGenFramebuffers(1, &mGaussianFrameBuffer);
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, mGaussianFrameBuffer);
    glGenTextures(1, &mGaussianRenderTexture);
    glBindTexture(GL_TEXTURE_2D, mGaussianRenderTexture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 
                        1024,
                        768, 
                        0, GL_RGBA, GL_UNSIGNED_BYTE,
                        NULL); 
    glBindTexture(GL_TEXTURE_2D, 0);
    glFramebufferTexture(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, mGaussianRenderTexture, 0);
    glGenTextures(1, &mGaussianDepthBuffer);
    glBindTexture(GL_TEXTURE_2D, mGaussianDepthBuffer);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 
                        1024,
                        768, 
                        0, GL_DEPTH_COMPONENT, GL_FLOAT,
                        NULL); 
    glBindTexture(GL_TEXTURE_2D, 0);
    glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, mGaussianDepthBuffer, 0);

这将返回成功的GL_FRAMEBUFFER_COMPLETE。

以下是有关渲染功能的三个方面：

    void Draw()
    {
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        //gluPerspective(45, 1024.0/768.0, 3.0, 20000);
        perspectiveGL(45, 1024.0/768.0, 1.0, 20000);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glPushMatrix();
        gluLookAt(cameraData[0],cameraData[1], cameraData[2],
                  cameraData[3],cameraData[4], cameraData[5],
                  0,1,0);

        glEnable(GL_DEPTH_TEST);
        glClearColor( 0.2f, 0.2f, 0.9f, 0.0f );
        glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  

        // OTHER STUFF POTENTIALLY DRAW HERE IN DIFFERENT WAYS

        glUseProgram(mEllipseTextureProgram);
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, mGaussianFrameBuffer);
        GLuint attachments[1] = {GL_COLOR_ATTACHMENT0};
        glDrawBuffers(1, attachments);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        DrawEllipseToTexture();
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
        glUseProgram(mScreenProgram);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        DrawTextureToScreen();
    }

    void DrawEllipseToTexture()
    {
        glEnableClientState(GL_VERTEX_ARRAY); 

        glBindBuffer(GL_ARRAY_BUFFER, mVBO);
        glVertexPointer(3, GL_FLOAT, 0, 0);

        glEnable(GL_PROGRAM_POINT_SIZE);

        glEnable(GL_POINT_SPRITE);

        glEnable( GL_TEXTURE_2D );
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, mBMP);
        glProgramUniform1i(mEllipseTextureProgram, mTextureLocation, 0);

        glBindBuffer(GL_ARRAY_BUFFER, mUV);
        glEnableVertexAttribArray(mTexCoordLocation);
        glVertexAttribPointer(mTexCoordLocation, 2, GL_FLOAT, GL_FALSE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER, mSpacial);
        glEnableVertexAttribArray(mSpacialLocation);
        glVertexAttribPointer(mSpacialLocation, 1, GL_FLOAT, GL_FALSE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER, mNormals);
        glEnableVertexAttribArray(mNormalLocation);
        glVertexAttribPointer(mNormalLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER, mVerticalSpat);
        glEnableVertexAttribArray(mMajorLocation);
        glVertexAttribPointer(mMajorLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER, mHorizontalSpat);
        glEnableVertexAttribArray(mMinorLocation);
        glVertexAttribPointer(mMinorLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);

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

        glDrawArrays(GL_POINTS, 0, mNumberPoints);

        glBindBuffer(GL_ARRAY_BUFFER, 0);

        glDisable( GL_TEXTURE_2D );
        glDisableVertexAttribArray(mSpacialLocation);
        glDisable(GL_POINT_SPRITE);
        glDisable( GL_POINT_SMOOTH );
        glDisable(GL_PROGRAM_POINT_SIZE);
        glDisableClientState(GL_VERTEX_ARRAY); 
    }

    void DrawTextureToScreen()
    {
        glEnableClientState(GL_VERTEX_ARRAY); 

        glEnable( GL_TEXTURE_2D );
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, mGaussianRenderTexture);
        glProgramUniform1i(mScreenProgram, mGaussianTextureLocation, 0);

        GLfloat vertices[] = { -1, -1, 2,
                               1, -1, 2,
                               1, 1, 2,
                               -1, 1, 2 };
        GLfloat uv[] = { 0, 0,
                        1, 0,
                        1, 1,
                        0, 1,};

        glVertexPointer(3, GL_FLOAT, 0, vertices);

        glEnableVertexAttribArray(mGaussianUV);
        glVertexAttribPointer(mGaussianUV, 2, GL_FLOAT, GL_FALSE, 0, uv);

        glDrawArrays(GL_TRIANGLES, 0, 4);

        glDisable ( GL_TEXTURE_2D );
        glDisableClientState(GL_VERTEX_ARRAY); 
    }

Answer 1

我仍然不知道上面我的解决方案出了什么问题（对此我做了很多尝试）-但是按照本教程进行操作可以使它起作用： 教程

Answer 2

我通常使用`out vec4 color'，不确定将纹理类型设置为GL_RGBA然后为每个片段返回vec3后，它是否会工作。

而且我没有看到您在代码中设置glViewport（），这意味着没有指定仿射变换来映射从NDC到屏幕空间的屏幕位置（x，y）。 如果在fbo渲染过程中没有视口，那绝对不会给您任何帮助。

我和您在类似情况下的挣扎一样。 阅读GL文档中不了解的功能，而不是博客，是正确理解事物的更好的方法...：）