opengl - GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT trying to create multisample framebuffer

Question

I'm trying to figure out how to create a framebuffer object that handles multisampling. Below is my attempt to get it working, but I keep getting GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT erros whenever I check my framebuffer status. I'm also getting this error even if I only attach the color buffer or only the depth/stencil buffer.

I've adapted this code from an older version without multisampling and which is able to create a complete framebuffer. I've left in those old calls but commented them out.

How do I set this up correctly?

void DocumentPanel::setupFramebuffer()
{
    QOpenGLFunctions_3_3_Core *f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_3_Core>();

    int w = width();
    int h = height();
    int samples = 16;

    if (_frameBufferID == 0)
    {
        f->glGenFramebuffers(1, &_frameBufferID);
        f->glBindFramebuffer(GL_FRAMEBUFFER, _frameBufferID);
    }

    if (_texBufferColor == 0)
    {
        // generate texture
        f->glGenTextures(1, &_texBufferColor);
        f->glBindTexture(GL_TEXTURE_2D, _texBufferColor);
        f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        f->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        f->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//        f->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
        f->glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, GL_RGBA8, w, h, false);
        f->glBindTexture(GL_TEXTURE_2D, 0);

        // attach it to currently bound framebuffer object
//        f->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texBufferColor, 0);
        f->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_MULTISAMPLE, _texBufferColor, 0);
    }

    if (_renderBufferDepthStencilID == 0)
    {
        f->glGenRenderbuffers(1, &_renderBufferDepthStencilID);
        f->glBindRenderbuffer(GL_RENDERBUFFER, _renderBufferDepthStencilID);
//        f->glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, w, h);
        f->glRenderbufferStorageMultisample(GL_RENDERBUFFER, samples, GL_DEPTH24_STENCIL8, w, h);
        f->glBindRenderbuffer(GL_RENDERBUFFER, 0);

        f->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, _renderBufferDepthStencilID);
    }

    GLenum status = f->glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE)
    {
        //error
        QString err;

        switch (status)
        {
        case GL_FRAMEBUFFER_UNDEFINED:
            err = "GL_FRAMEBUFFER_UNDEFINED";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
            err = "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT :
            err = "GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT ";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER :
            err = "GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER ";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER :
            err = "GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER ";
        break;
        case GL_FRAMEBUFFER_UNSUPPORTED :
            err = "GL_FRAMEBUFFER_UNSUPPORTED ";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE :
            err = "GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE ";
        break;
        case GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS  :
            err = "GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS  ";
        break;
        }

        f->glBindFramebuffer(GL_FRAMEBUFFER, 0);

        qDebug() << "Error building frambuffer: " << err;
        return;
    }

    //Rendering to window again
    f->glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

question from:https://stackoverflow.com/questions/65866554/gl-framebuffer-incomplete-attachment-trying-to-create-multisample-framebuffer

Answer 1

GL_TEXTURE_2D and GL_TEXTURE_2D_MULTISAMPLE are different texture targets. Your code binds the texture to GL_TEXTURE_2D, but then tries to operate on it through GL_TEXTURE_2D_MULTISAMPLE, which cannot work.

Instead you should change ALL the targets to GL_TEXTURE_2D_MULTISAMPLE:

    f->glGenTextures(1, &_texBufferColor);
    f->glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, _texBufferColor);
    f->glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, GL_RGBA8, w, h, false);
    f->glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, 0);