【发布时间】：2019-10-15 06:00:53
【问题描述】：
我们的目标是用 Qt3D 替换我们之前的 3D 引擎。作为最后一个障碍，我们需要正确实现像素正确的透明度。我们现在正尝试将深度剥离作为一种可能的方法来使像素正确的透明度可行。对于此算法，必须执行延迟（多通道）渲染，这可以通过在效果内使用QRenderPassFilter 和QFilterKey 来实现。
现在，要使QRenderPassFilter 和QFilterKey 与材料QDiffuseSpecularMaterial 的组合能够正常工作，我已经遇到了很大的问题。即使只有一次通过。
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，如果我删除该行
renderPassFilter->addMatch(filterKey);
一切正常，我看到了我的简单平面网格。
但是，添加不应过滤任何内容的线不再显示平面网格。
我真的没有想法了，我可能在这里做错了什么。如何，我可以用我的renderPassFilter 制作我的小程序，我的错误是什么？
我也不太明白，QFilterKey中设置name和value的目的是什么，需要过滤掉某些效果？
【问题讨论】：