使用 QPainter 时对象是透明的

问题描述

所以我尝试在我的对象上贴上标签。我尝试了一个测试示例，只是在那里放了一个简单的标签。然而，当我运行程序时，所有对象都有些透明。

paintGL：

void mainWidget::paintGL(){
    QPainter painter(this);
    painter.beginNativePainting();
    glClearColor(0.0f,0.0f,1.0f);

    glViewport(0,width(),height());

    projection = camera->getProjectionMatrix(60.0f,height(),0.1f,100.0f);
    vec3 cameraPos(camera->getPosition());
    view = camera->getViewMatrix();

    glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    if (isLine)
        glpolygonMode(GL_FRONT_AND_BACK,GL_LINE);
    shaderProgram->bind();
    shaderProgram->setUniformValue("Light.ambient",0.1f);
    shaderProgram->setUniformValue("Light.position",QVector3D(ld[0],ld[1],ld[2]));
    model = mat4(1.0f);
    model = glm::translate(model,modelOrigin + cubePosModel);
    setRotModel(cubeRotModel);
    setMatrices(shaderProgram,true);
    shaderProgram->setUniformValue("viewPosition",QVector3D(cameraPos[0],cameraPos[1],cameraPos[2]));

    if (showCube) 
        cubeMesh->render(shaderProgram);
    shaderProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_FILL);
    if (isLine)
        glpolygonMode(GL_FRONT_AND_BACK,GL_LINE);
    view = camera->getViewMatrix();
    model = mat4(1.0f);
    model = glm::translate(model,modelOrigin + planePosModel);

    setRotModel(planeRotModel);
    shaderProgram->bind();
    setMatrices(shaderProgram,cameraPos[2]));
    if (showPlane)
        planeMesh->render(shaderProgram);
    shaderProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_LINE);
    model = glm::mat4(1.0f);
    model = glm::translate(model,modelOrigin + teapotPosModel);
    setRotModel(teapotRotModel);

    shaderProgram->bind();
    setMatrices(shaderProgram,true);
    if (showTeapot)
        teapotMesh->render(shaderProgram);
    shaderProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_FILL);

    model = glm::mat4(1.0f);
    model = glm::translate(model,modelOrigin + cubeLightPosModel);
    model = glm::scale(model,glm::vec3(0.3f));
    setRotModel(cubeLightRotModel);

    lightCubeProgram->bind();
    setMatrices(lightCubeProgram,false);
    if (showCubeLight)
        cubeMesh->render(lightCubeProgram);
    lightCubeProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_LINE);

    axis_vao->bind();
    model = mat4(1.0f);
    model = glm::translate(model,modelOrigin);
    model = glm::scale(model,vec3(5.0f));
    model = glm::rotate(model,glm::radians(2.0f),vec3(1,1,0));
    drawAxisProgram->bind();
    glm::mat4 pvm = projection * view * model;
    drawAxisProgram->setUniformValue("mvpMatrix",QMatrix4x4(glm::value_ptr(pvm)).transposed());
    if (showGrid)
        glDrawArrays(GL_LInes,axisSize);
    axis_vao->release();
    drawAxisProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_FILL);

    if (isLine)
        glpolygonMode(GL_FRONT_AND_BACK,GL_LINE);
    model = mat4(1.0f);
    model = glm::translate(model,modelOrigin + vec3(0,2,-1));
    shaderProgram->bind();
    setMatrices(shaderProgram,true);
    if (showSphere)
        sphereMesh->render(shaderProgram);
    shaderProgram->release();
    glpolygonMode(GL_FRONT_AND_BACK,GL_FILL);

    painter.endNativePainting();
    painter.setPen(Qt::yellow);
    painter.setFont(QFont("Helvetica",8));
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    painter.drawText(200,400,"Scene Maker"); // z = pointT4.z + distOverOp / 4
    painter.end();
}

我不知道为什么，但它是唯一透明的物体。此外，QPainter 的添加使茶壶的盖子有些混乱。也许这与正在进行的 glpolygonMode 乱七八糟的东西有关？

万一是 QPainter 偷偷禁用了 GL_DEPTH_TEST（似乎是这种情况），我后来重新启用了它，但它仍然不起作用。

mainWidget 是一个 qopenglwidget。

那么，问题是什么？ 图片：

（如您所见，网格线透过茶壶显示出来，但立方体没有显示出来，使其不完全透明。）

编辑：我发现所有其他对象也是透明的。

解决方法

您的深度测试被禁用或您的上下文没有深度缓冲区。首先确保在初始化期间使用深度缓冲区设置像素格式。 QOpenGLWidget documentation 有一个例子：

QOpenGLWidget *widget = new QOpenGLWidget(parent);
QSurfaceFormat format;
format.setDepthBufferSize(24); // <--- this is what you need
format.setStencilBufferSize(8);
format.setVersion(3,2);
format.setProfile(QSurfaceFormat::CoreProfile);
widget->setFormat(format); // must be called before the widget or its parent window gets shown

接下来在您的绘图代码中启用深度测试：

glEnable(GL_DEPTH_TEST);