[Development] Qt3D. How to change the speed of camera motion?

[Dmitrii Volosnykh]

Read
"primary task that discoverd issued being discussed"
as
"primary task that discovered the issue under discussion"

Sorry, for mistakes.

2013/4/3 Dmitrii Volosnykh <dmitrii.volosnykh at gmail.com>:
> Hi,
>
> first of all, I realize that Qt3D is a premature module and targeted
> for 5.2 release. Anyway, it is already a wealthy piece of work that
> can be used for some cases.
>
> The default settings regarding motion of camera are not suitable for
> me (i.e. panning using mouse is way too slow).
>
> Looking in sources, I've found that such user interaction is done via
> QGLView::wheel(), pan(), and rotate(). So, it would be possible to,
> for example, accelerate camera motion by multiplying parameters of
> these functions before actually calling them. Unforunately, all of
> them are private to QGLView.
>
> To try it other way, it could be possible to tweak viewDelta() to
> return its value multiplied by a factor or pass tweaked arguments to
> base class's version of veiwDelta(). Despite viewDelta() is protected
> and visible from derived class (while being used only inside QGLView
> and nowhere else), it is not virtual, hence can not be reimplemented.
> Even if it would, its reimplementaion would affect all of the wheel(),
> pan, and rotate() methods. I am not sure that this is always a good
> idea.
>
> To achieve my goal anyhow, I had to make a verbose copy of pan()
> method in my derived class. Thanks to the fact that viewDelta() is
> protected, else this work around would not do the job.
>
> Another disadvantage is that, as for me, I can not find a way to
> preserve internal logic in QGLView::mouseMoveEvent() regarding private
> panning-relative data (such as startPan, lastPan, panModifiers, etc.).
> This means that I have to reinvent the wheel and code all that stuff
> in order to call pan() with tweaked parameters from my
> reimplementation of mouseMoveEvent(). Of course, that looks very ugly
> and frustrates me.
>
> Cloning of pan() method in derived class is directly avoidable by
> making QGLVew::pan() be protected. And the issue with reimplementing
> mouseMoveEvent() is, probably, solvable by making pan(), wheel(),
> rotate() methods being virtual. Maybe, Method viewDelta() is also
> could be virtual in order to allow change behaviour of all three
> methods in one place.
>
> Another solutions is probably in exposing through QGLView's interface
> some properties like panFactor, wheelFactor, rotateFactor. Maybe, this
> is the most easiest way to achive the primary task that discoverd
> issued being discussed: to change the speed of camera motion. In this
> case, all access qualifiers and absense of 'virtual' modifier can
> remain unchanged.
>
> Regards,
> Dmitrii.