Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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5.13.0
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None
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All
Description
The following code shows a 3D Scene with two spheres with centers at (20,-10,0) and (20,10,0) and radii 0.5.
Both spheres are below an empty QEntity called rootEntity.
Calling viewEntity on this rootEntity, should result in a spherical bounding volume centered at (20,0,0) with radius (20+2*0.5)/2.
Instead the program returns:
Bounding Sphere: QVector3D(12.1432, 2.14455, -1.32699e-08) 14.9644
Calling viewEntity on sphere1 and sphere2 gave the desired results of:
Bounding Sphere: QVector3D(20, 10, -2.18557e-08) 0.5
Bounding Sphere: QVector3D(20, -10, -2.18557e-08) 0.5
My best guess is that there is an error inside the ComputeFilteredBoundingVolumeJob.cpp on lines 61-68, but I was not able to nail it down.
#include <QApplication>
#include <QWidget>
#include <QLoggingCategory>
#include <QVBoxLayout>
#include <QFrame>
#include <Qt3DRender/QRenderSettings>
#include <Qt3DCore/QTransform>
#include <Qt3DRender/QCamera>
#include <Qt3DExtras/QSphereMesh>
#include <Qt3DExtras/QDiffuseSpecularMaterial>
#include <Qt3DExtras/QForwardRenderer>
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DRender/QCamera>
#include <Qt3DRender/QCameraLens>
#include <QPushButton>
Qt3DCore::QEntity* createSphereMesh()
{
auto sphereMat = new Qt3DExtras::QDiffuseSpecularMaterial;
sphereMat->setDiffuse(QColor(Qt::blue));
auto mesh = new Qt3DExtras::QSphereMesh();
mesh->setRadius(0.5);
auto meshEntity = new Qt3DCore::QEntity;
meshEntity->addComponent(mesh);
meshEntity->addComponent(sphereMat);
return meshEntity;
}
int main(int argc, char* argv[])
{
QApplication a(argc, argv);
auto view = new Qt3DExtras::Qt3DWindow();
view->defaultFrameGraph()->setClearColor(QColor(127, 127, 127));
auto settings = view->renderSettings();
settings->setActiveFrameGraph(view->activeFrameGraph());
auto rootEntity = new Qt3DCore::QEntity();
view->setRootEntity(rootEntity);
auto sphere1 = createSphereMesh();
sphere1->setParent(rootEntity);
auto trafo1 = new Qt3DCore::QTransform;
trafo1->setTranslation(QVector3D(20, 10, 0));
sphere1->addComponent(trafo1);
auto sphere2 = createSphereMesh();
sphere2->setParent(rootEntity);
auto trafo2 = new Qt3DCore::QTransform;
trafo2->setTranslation(QVector3D(20, -10, 0));
sphere2->addComponent(trafo2);
QObject::connect(view->camera()->lens(), &Qt3DRender::QCameraLens::viewSphere, [&](const QVector3D& center, float radius) {
qDebug() << "Bounding Sphere:" << center << radius;
auto boundingSphereEntity = new Qt3DCore::QEntity;
auto sphereMat = new Qt3DExtras::QDiffuseSpecularMaterial;
sphereMat->setAlphaBlendingEnabled(true);
sphereMat->setDiffuse(QColor(255,255,255,80));
auto mesh = new Qt3DExtras::QSphereMesh();
mesh->setRadius(radius);
boundingSphereEntity->addComponent(sphereMat);
boundingSphereEntity->addComponent(mesh);
auto trafoAll = new Qt3DCore::QTransform;
trafoAll->setTranslation(center);
boundingSphereEntity->addComponent(trafoAll);
boundingSphereEntity->addComponent(mesh);
boundingSphereEntity->addComponent(sphereMat);
boundingSphereEntity->setParent(rootEntity);
});
auto container = QWidget::createWindowContainer(view);
auto viewAllBtn = new QPushButton("View Root Entity");
QObject::connect(viewAllBtn, &QPushButton::clicked, [&]() {
view->camera()->viewEntity(rootEntity);
});
QFrame frame;
frame.setFixedSize(500, 500);
frame.setLayout(new QVBoxLayout);
frame.layout()->addWidget(container);
frame.layout()->addWidget(viewAllBtn);
frame.show();
return a.exec();
}
I further investigated, as I really needed this feature and stumbled across the source tst_boundingsphere.cpp in qt3d/tests/auto/render/boundingsphere.
There I found the following interesting line:
| QTest::newRow("CubeMesh") << "qrc:/cube.qml" << QVector3D(0.0928356f, -0.212021f, -0.0467958f) << 1.07583f; // weird! |
It is indeed not obvious, why a cube mesh of extents 1. should have a bounding volume like this. At least the radius of the bounding sphere should be sqrt(3)/2. The center of the cube should be something like (0.5,0.5,0.5).
I guess the problem lies in the implementation of the qt3d/src/render/frontend/sphere.cpp, as there is a fault in the implementation of an invalid sphere. Assume that there is an void entity without any points, then it will have a bounding sphere with center=(0,0,0) with r=0. Assume now, that you will another bounding sphere with center=(1,1,1) and r=0.1.
Then expandToContain should just give center=(1,1,1) and r=0.1, but expandToContain will give something around center=(0.55,0.55,0.55) and r=0.55.
I would suggest to implement invalid spheres being the ones having a radius being < 0.
In case the method transformed is called on an invalid sphere, there should be nothing to do.