Horde3D Particle System not rendering in Qt OpenGL - qt

Question

Horde3d come with 2 samples, compiled with GLFW. One of them, Knight, shows a particle emitter. I've ported the samples to Qt, with a thin layer I wrote that leave unchanged the applicative code (i.e. scene setup, rendering and events handling).
Indeed, the functionality is ok, except the particle emitter doesn't show. I can't see anything specific in GLFW initialization, and I tried some setting I found in Qt, without success. Horde3d takes care of OpenGL interface, and expose a higher level, clean C interface. Any clue?
EDIT : Most Rilevant Sources of qtKnight.pro
here (cleaned :) main.cpp
#include "glwidget.h"
#include <QApplication>
int main(int argc, char* argv[]) {
QApplication app(argc, argv);
GLWidget glw;
glw.show();
return app.exec();
}
here glWidget.h
#ifndef GL_WIDGET_H
#define GL_WIDGET_H
#include <QtOpenGL>
#include <QTimer>
#include <QKeyEvent>
#include <Horde3D.h>
#include <Horde3DUtils.h>
#include <sstream>
#include <app.h>
class GLWidget : public QGLWidget, Application {
Q_OBJECT
public:
GLWidget();
~GLWidget();
QSize minimumSizeHint() const { return sizeHint(); }
QSize sizeHint() const { return QSize(640, 480); }
protected:
void initializeGL();
void paintGL();
void resizeGL(int width, int height);
void mousePressEvent(QMouseEvent *event);
void mouseMoveEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
void keyPressEvent(QKeyEvent *e) { keyEvent(e, true); QGLWidget::keyPressEvent(e); }
void keyReleaseEvent(QKeyEvent *e) { keyEvent(e, false); QGLWidget::keyReleaseEvent(e); }
void keyEvent(QKeyEvent *, bool);
public slots:
void appLoop() { updateGL(); }
private:
QPoint lastPos;
QTimer evloop;
};
#endif
and here glWidget.cpp
#include "glwidget.h"
#include <stdexcept>
#include <QtDebug>
#include <QTextStream>
#include <QGLFormat>
GLWidget::GLWidget() :
QGLWidget(QGLFormat(QGL::AlphaChannel | QGL::SampleBuffers)),
Application("/home/carlo/horde3d/SDK_1.0.0_Beta5/Horde3D/Binaries/Content")
{
connect(&evloop, SIGNAL(timeout()), this, SLOT(appLoop()));
evloop.start(0);
}
GLWidget::~GLWidget()
{
h3dutDumpMessages();
h3dRelease();
}
void GLWidget::initializeGL()
{
if (!init())
throw std::runtime_error("Could not initialize renderer");
}
void GLWidget::paintGL()
{
keyStateHandler();
mainLoop(30);
}
void GLWidget::resizeGL(int width, int height)
{
Application::resize(width, height);
}
void GLWidget::mousePressEvent(QMouseEvent *event)
{
lastPos = event->pos();
}
void GLWidget::mouseMoveEvent(QMouseEvent *event)
{
QPoint cPos = event->pos();
float dX = cPos.x() - lastPos.x(); //event->x() - lastPos.x();
float dY = cPos.y() - lastPos.y(); //event->y() - lastPos.y();
Application::mouseMoveEvent(dX, dY);
lastPos = cPos;
}
void GLWidget::mouseReleaseEvent(QMouseEvent * /* event */)
{
}
void GLWidget::keyEvent(QKeyEvent *k, bool on_off)
{
#define setK(X,Y) case Qt::X: setKeyState(Y, on_off); break;
#define setF(X) case Qt::Key_##X: setKeyState(X, on_off); break;
#define R(X, Y) (v >= #X[0] && v <= #Y[0])
int v = k->key();
switch (v) {
case Qt::Key_F1: if (on_off) showFullScreen(); break;
case Qt::Key_F2: if (on_off) showNormal(); break;
setF(F3)
setF(F6)
setF(F7)
setF(F8)
setK(Key_Space, SP)
default:
if (R(A, Z) || R(0, 9))
setKeyState(v, on_off);
}
}

Answer 1

Since you say it is only the particles that aren't shown, it could have to do with alpha blending. I also saw from your code that you don't specify a format when constructing the QGLWidget, in which case the default format is used which explicitly disables the alpha channel.
Though I don't know if this has any effect (shouldn't there always be an A in RGBA?), but maybe this really requests a pixel format where there is no storage for the A channel, in which case things like alpha blending (used for the transparent particles) won't work.
So just try to request it explicitly by using an appropriate format in the QGLWidget constructor:
GLWidget::GLWidget()
: QGLWidget(QGLFormat(QGL::AlphaChannel))
You actually were on the right track with your outcommented QGLFormat argument, but it hasn't anything to do with the HasOverlay option, which you don't really need, as Horde3d does it's own overlay rendering.