3D Graphics Performance Optimization Techniques

Although the tips in the following link are only concerning DirectX9, it may still be useful in Qt:

https://msdn.microsoft.com/en-us/library/windows/desktop/bb147263(v=vs.85).aspx

Notably:

  • Only redraw to the image buffer when you need to
  • Use smaller textures
  • Draw objects from front to back
  • Constantly test your code’s performance
  • Use one large array/buffer of vertices
  • Draw only what needs to be drawn, so culling and z-ordering can only help more

The ideal is to get a higher framerate which is perceivably better experience for the user. For 2D graphics, 16 frames per second is satisfactory. But for 3D graphics, 30 frames per second seems to be tolerable, but 60 frames per second is the minimal. But if you’re just learning 3D graphics programming, don’t worry about frames per second, just worry about the geometry and math to make sure it is correct. Then you can optimize it when you’re confident you understand how it all works.

Windows 10 drops support for Qt 4.8.x after Qt.4.8.6

The main reason I had to rollback to using Qt 4.8.5 since I was developing on Qt 4.8.7 on a Windows 7 machine was because after upgrading to Windows 10, my 4.8.7 apps failed in so many levels. Something as simple as loading an image was completely broken. I did a little digging and it turns out since Qt 4.8.6, support for versions of Windows before version 10 was dropped. So instead of gambling with newer versions of Qt that just won’t work on my “old” development Windows machine, I have to count on the versions of Qt that will. And Qt 4.8.5 was the last functioning version that seemed to be supported by most Windows versions.

How To Read EXIF Orientation From JPEG in Qt 4.8.5

For many Qt lovers out there who might want to use third-party EXIF parsing library with their Qt apps, it may prove difficult unless you know what you’re doing. If you’re a hobbyist like me, man, it’s just tough. But there are free EXIF parsers out there, and it might take a little elbow grease to make it work with Qt. In my case, I put together a very simple and basic image viewer that I thought users might appreciate if it auto-rotated any images that contained EXIF metadata such as orientation. In smartphones and DSLRs, there is usually a sensor that records which orientation the picture was taken in. So when you view the photo without orientation applied, it might be a minor nuisance having to manually rotate it. That’s where you come in as software developer and take care of it for the end-user. Continue reading “How To Read EXIF Orientation From JPEG in Qt 4.8.5”

Fixing Windows 10 Aspect Ratio Scaling Problem For Lower Resolution Display

You may notice if you’re still deploying applications using resolutions less than 800x600x72dpi on Windows 10 that the autoscaling for the aspect ratio might be wonky. That’s because all these new fancy operating systems are trying to cater to ultra high resolution/density screens these days, and if you’re building an old-fashion 2D game engine that doesn’t require too much screen resolution, the final output might be thrown off a bit. Sometimes it’s just the graphics card, but in Windows 10 case, it seems it’s built into the operating system. Anyway, this is how I “fixed” it.

Example of incorrect aspect ratio in Windows 10 auto-scaling fullscreen
Example of incorrect aspect ratio in Windows 10 auto-scaling fullscreen

Continue reading “Fixing Windows 10 Aspect Ratio Scaling Problem For Lower Resolution Display”

How to generate random number in Qt

If you thought Qt provided you with a robust count of math algorithms already, you’ll be in for a surprise. There is qrand(), but it doesn’t quite provide you with the user-friendliness of other languages. For example, sometimes you want a random number that is negative. Sure, you can do this all manually, but then you’d have to write your own function. Unfortunately, that’s exactly what you’ll have to do.

http://developer.nokia.com/Community/Wiki/Generating_random-value_integers_in_Qt

#include <QGlobal.h>
#include <QTime>

int QMyClass::randInt(int low, int high)
{
// Random number between low and high
return qrand() % ((high + 1) - low) + low;
}

// Create seed for the random
// That is needed only once on application startup
QTime time = QTime::currentTime();
qsrand((uint)time.msec());

// Get random value between 0-100
int randomValue = randInt(0,100);

It is recommended that you don’t use qrand() by default if you want to generate encryption-level random numbers.

So, with that code, now you can set a range of numbers which you can pull random numbers from. Make note that qsrand() only sets the seed and you should only do that once.

Overriding QWidget Events

For the most part, Qt comes with a bunch of convenience widgets built on top of their own QWidget. They may provide very specific features and might suit your needs perfectly. But when you want to implement something that is really unique, then you’ll have to be able to engage the internal processes that make your user-friendly interactions so intuitive. One way is to override QWidget’s default events. Continue reading “Overriding QWidget Events”