即使QFilterKey匹配，QRenderPassFilter也会隐藏平面网格

Question

我们的目标是用Qt3D取代以前的3D引擎。作为最后一个障碍，我们需要正确地实现像素正确的透明度。我们现在正在尝试实现深度剥离，作为一种可能的方法，使像素校正透明度可行。对于此算法，必须执行延迟(多通道)渲染，这可以在效果中使用QRenderPassFilter和QFilterKey来实现。

现在，我已经遇到了很大的问题，使得QRenderPassFilter和QFilterKey的组合以及material QDiffuseSpecularMaterial能够正常工作。即使只有一次传球。

这是我的源代码：

#include <QApplication>
#include <QWidget>
#include <QVBoxLayout>
#include <QFrame>
#include <Qt3DCore/QTransform>
#include <Qt3DRender/QSortPolicy>
#include <Qt3DRender/QRenderSettings>
#include <Qt3DRender/QRenderSurfaceSelector>
#include <Qt3DRender/QViewport>
#include <Qt3DRender/QCamera>
#include <Qt3DRender/QCameraSelector>
#include <Qt3DRender/QClearBuffers>
#include <Qt3DRender/QDirectionalLight>
#include <Qt3DRender/QTexture>
#include <Qt3DExtras/QPlaneMesh>
#include <Qt3DExtras/QDiffuseSpecularMaterial>
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DRender/QFilterKey>
#include <Qt3DRender/QParameter>
#include <Qt3DRender/QRenderPass>
#include <Qt3DRender/QRenderPassFilter>
#include <Qt3DRender/QTechnique>
#include <QDebug>

int main(int argc, char* argv[])
{
    QApplication a(argc, argv);

    auto view = new Qt3DExtras::Qt3DWindow();
    auto mClearBuffers = new Qt3DRender::QClearBuffers;
    auto mMainCameraSelector = new Qt3DRender::QCameraSelector;
    mMainCameraSelector->setCamera(view->camera());
    auto mRenderSurfaceSelector = new Qt3DRender::QRenderSurfaceSelector;
    auto mMainViewport = new Qt3DRender::QViewport;

    auto renderPassFilter = new Qt3DRender::QRenderPassFilter;
    {
        auto filterKey = new Qt3DRender::QFilterKey(renderPassFilter);
        filterKey->setName(QStringLiteral("renderingStyle"));
        filterKey->setValue(QStringLiteral("forward"));
        // Adding the filterKey to the renderPassFilter hides the plane
        // Name and Value of filterKey matches the FilterKey inside the QDiffuseSpecularMaterial
        renderPassFilter->addMatch(filterKey); // Removing this lines shows the plane mesh

        mClearBuffers->setClearColor(Qt::lightGray);
        mClearBuffers->setBuffers(Qt3DRender::QClearBuffers::BufferType::ColorDepthBuffer);
        mMainCameraSelector->setParent(mClearBuffers);
        mClearBuffers->setParent(renderPassFilter);
    }
    renderPassFilter->setParent(mRenderSurfaceSelector);

    mRenderSurfaceSelector->setParent(mMainViewport);

    view->setActiveFrameGraph(mMainViewport);
    view->activeFrameGraph()->dumpObjectTree();

    auto rootEntity = new Qt3DCore::QEntity();
    view->setRootEntity(rootEntity);

    view->camera()->lens()->setPerspectiveProjection(45.0f, 1., 0.1f, 10000.0f);
    view->camera()->setPosition(QVector3D(0, 2, 0));
    view->camera()->setUpVector(QVector3D(0, 1, 0));
    view->camera()->setViewCenter(QVector3D(0, 0, 0));

    auto planeEntity = new Qt3DCore::QEntity(rootEntity);

    auto meshMaterial = new Qt3DExtras::QDiffuseSpecularMaterial;
    meshMaterial->setDiffuse(QColor("#ff00ff"));
    planeEntity->addComponent(meshMaterial);

    auto mesh = new Qt3DExtras::QPlaneMesh;
    mesh->setWidth(0.3);
    mesh->setHeight(0.3);
    planeEntity->addComponent(mesh);

    auto container = QWidget::createWindowContainer(view);
    QFrame frame;
    frame.setLayout(new QVBoxLayout);
    frame.layout()->addWidget(container);
    frame.resize(QSize(400, 300));

    frame.show();
    return a.exec();
}

控制台将我的框架图输出为：

Qt3DRender::QViewport::
    Qt3DRender::QRenderSurfaceSelector::
        Qt3DRender::QRenderPassFilter::
            Qt3DRender::QFilterKey::
            Qt3DRender::QClearBuffers::
                Qt3DRender::QCameraSelector::

现在，如果我删除这行

renderPassFilter->addMatch(filterKey);

一切都像预期的一样，我看到了我的简单平面网格。

但是，添加不会过滤任何内容的直线平面网格将不再显示。

我真的没有想法了，我可能在这里做错了什么。如何让我的小程序与我的renderPassFilter一起工作，我的错误是什么？

我也不太明白，在QFilterKey中设置name和value的目的是什么，哪两个是过滤某些效果所必需的？

Answer 1

仔细研究了我的应用程序，特别是QDiffuseSpecularMaterial之后，我发现QDiffuseSpecularMaterial中的QFilterKey并没有添加到QRenderPass对象中，而是添加到了我觉得相当晦涩难懂的QTechnique中。

现在，添加QTechniqueFilter而不是QRenderPassFilter使程序按预期工作。将字符串forward更改为不同的值，例如xxx会按预期隐藏平面。

添加行

meshMaterial->dumpObjectTree();

确实给了我线索

Qt3DExtras::QDiffuseSpecularMaterial::
    Qt3DRender::QShaderProgramBuilder::
        Qt3DRender::QShaderProgram::
    Qt3DRender::QShaderProgramBuilder::
        Qt3DRender::QShaderProgram::
    Qt3DRender::QFilterKey::
    Qt3DRender::QEffect::
        Qt3DRender::QTechnique::
            Qt3DRender::QRenderPass::
                Qt3DRender::QNoDepthMask::
                Qt3DRender::QBlendEquationArguments::
                Qt3DRender::QBlendEquation::
        Qt3DRender::QTechnique::
            Qt3DRender::QRenderPass::
        Qt3DRender::QTechnique::
            Qt3DRender::QRenderPass::
        Qt3DRender::QParameter::
        Qt3DRender::QParameter::
        Qt3DRender::QParameter::
        Qt3DRender::QParameter::
        Qt3DRender::QParameter::

因此，在处理Qt3D和Qt时，dumpObjectTree()似乎是一个很好的工具。

#include <QApplication>
#include <QWidget>
#include <QVBoxLayout>
#include <QFrame>
#include <Qt3DCore/QTransform>
#include <Qt3DRender/QSortPolicy>
#include <Qt3DRender/QRenderSettings>
#include <Qt3DRender/QRenderSurfaceSelector>
#include <Qt3DRender/QViewport>
#include <Qt3DRender/QCamera>
#include <Qt3DRender/QCameraSelector>
#include <Qt3DRender/QClearBuffers>
#include <Qt3DRender/QTechniqueFilter>
#include <Qt3DRender/QDirectionalLight>
#include <Qt3DRender/QTexture>
#include <Qt3DExtras/QPlaneMesh>
#include <Qt3DExtras/QDiffuseSpecularMaterial>
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DRender/QFilterKey>
#include <Qt3DRender/QParameter>
#include <Qt3DRender/QRenderPass>
#include <Qt3DRender/QRenderPassFilter>
#include <Qt3DRender/QTechnique>
#include <QDebug>

int main(int argc, char* argv[])
{
    QApplication a(argc, argv);

    auto view = new Qt3DExtras::Qt3DWindow();
    auto mClearBuffers = new Qt3DRender::QClearBuffers;
    auto mMainCameraSelector = new Qt3DRender::QCameraSelector;
    mMainCameraSelector->setCamera(view->camera());
    auto mRenderSurfaceSelector = new Qt3DRender::QRenderSurfaceSelector;
    auto mMainViewport = new Qt3DRender::QViewport;
    auto renderPassFilter = new Qt3DRender::QTechniqueFilter;
    {
        auto filterKey = new Qt3DRender::QFilterKey(renderPassFilter);
        filterKey->setName(QStringLiteral("renderingStyle"));
        filterKey->setValue(QStringLiteral("forward"));
        // Adding the filterKey to the renderPassFilter hides the plane
        // Name and Value of filterKey matches the FilterKey inside the QDiffuseSpecularMaterial
        renderPassFilter->addMatch(filterKey); // Removing this lines shows the plane mesh

        mClearBuffers->setClearColor(Qt::lightGray);
        mClearBuffers->setBuffers(Qt3DRender::QClearBuffers::BufferType::ColorDepthBuffer);
        mMainCameraSelector->setParent(mClearBuffers);
        mClearBuffers->setParent(renderPassFilter);
    }
    renderPassFilter->setParent(mRenderSurfaceSelector);

    mRenderSurfaceSelector->setParent(mMainViewport);

    view->setActiveFrameGraph(mMainViewport);
    view->activeFrameGraph()->dumpObjectTree();

    auto rootEntity = new Qt3DCore::QEntity();
    view->setRootEntity(rootEntity);

    view->camera()->lens()->setPerspectiveProjection(45.0f, 1., 0.1f, 10000.0f);
    view->camera()->setPosition(QVector3D(0, 2, 0));
    view->camera()->setUpVector(QVector3D(0, 1, 0));
    view->camera()->setViewCenter(QVector3D(0, 0, 0));

    auto planeEntity = new Qt3DCore::QEntity(rootEntity);

    auto meshMaterial = new Qt3DExtras::QDiffuseSpecularMaterial;
    meshMaterial->setDiffuse(QColor("#ff00ff"));
    planeEntity->addComponent(meshMaterial);

    auto mesh = new Qt3DExtras::QPlaneMesh;
    mesh->setWidth(0.3);
    mesh->setHeight(0.3);
    planeEntity->addComponent(mesh);

    auto container = QWidget::createWindowContainer(view);
    QFrame frame;
    frame.setLayout(new QVBoxLayout);
    frame.layout()->addWidget(container);
    frame.resize(QSize(400, 300));

    frame.show();
    return a.exec();
}