[Development] StereoViewport for Qt3D

Svenn-Arne Dragly s at dragly.com
Thu Nov 21 10:17:52 CET 2013

On to. 21. nov. 2013 kl. 09.40 +0100, Fabian Bumberger wrote:
>>> while working on this, the temporary frame buffer used for picking 
>>> had a size set to 8x8 pixels(!).
> For picking the whole scene is rendered using the pick painter for 
> every performed pick. And afaik, if you swich on picking then a pick 
> is performed for every mouse event (including mouse move events). So I 
> guess having such a small FBO was because of performance and memory 
> reasons. But I also noticed that picking is quite unreliable with that.

I think you are absolutely right - the new implementation will be a 
performance hit, but it is reliable.

The previous implementation appears to render only a smaller part of the 
viewport for picking (around the mouse cursor). It might be that a bug 
in this implementation was causing it to be unreliable? In any case, the 
previous implementation was more complicated, making it harder to 
maintain and harder to build upon for stereoscopic viewing, in my opinion.

What I could do to yield better performance is to reuse the picking 
buffer from last time if it the scene has not changed. That way the same 
scene should be painted only twice - once for the view and once for the 
picking buffer. This is what is done in QGLView.


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