Hello,

Foreword, as this may (or may not) be of importance : I use the stabilizer feature (not basic/weighted smoothing, but the stabilizer) when using a brush, simply because I am an ex SAI user and I despite my best efforts, I couldn't draw without having a very little lag (because in SAI, the stabilizer makes you brush lag a little, very similar to the way it works in Krita when you have a short distance and delay ticked off).

Ok so, as the thread's title say, when I zoom in a document (usually a large one, >2000x1000, but it also happens in 1920x1080 pictures but only after I opened a large document), then rotate the drawing to a certain angle (anything that is not 0, 90, 180, -180, -90), the brush starts lagging a lot more than it should.
To show the difference I made a small comparison video :
http://webmshare.com/oKKgY
In this video, I first draw a shape to show that Krita works fine, then rotate the canvas by 15° then draw the shape again, then I repeat it a few times until we reach 90° and it works just fine again. I tried to do the same motion with my hand every time in the video, if the result look different from the first shape, it is because of that problem.

I am using Krita 2.9.10 Animation Edition (beta), but this was also present in 2.9.x (I have tried them all). I dual boot, so I tested it on both Windows 7 and Linux Mint, same result.
I made my friend try the same thing in his Krita (version 2.9.7), and he says he doesn't have that lag.

What could cause this?
Thanks in advance!

Is that with opengl enabled or disabled, and what is the colormodel and channel depth you are using?

OpenGL is enabled, and my color model is RGB (8bit integer/channel). The channel depth is 8 bits.
I don't recall modifying these options after installing Krita (all I did is the usual stuff, change shortcuts and added a little more memory to the memory limit (50% of my system, about 8gb) because I have a lot of RAM), so they should all be the default ones.

This is probably the fault of the drivers then. We have noticed than certain drivers try to fake supporting certain OpenGL functions by implementing them in a very slow way(we call this 'software rendering'), and there's not much we can do about it.

What you can try to do is to go to settings->configure Krita->display and turn down the OpenGL filtering to trilinear or bilinear. It will look bad zoomed out, but the canvas should be faster.

I tried every setting in openGL, but none really changed anything to the lag (I even restarted Krita everytime to make sure). only turning off openGL completely removed the lag, so there is definitely something going on with it.
but if my drivers were faking to support openGL, wouldn't my strokes have lag whatever angle I use? here I only get lag at certain angles (and 90, 180, 270° are fine, it's just the angles between that lag heavily).

Well, no. For angles other than straight, the gpu has to do much more complicated maths... And that might, on some systems, slow things down. It's like the difference between you dividing 10 by 2 in your head, or 10 by 1.753

i also have this with 2.9.8, try to override or enhance the application settings for anti-aliasing in your driver settings every setting seems to remove the lag for me, but if i set it to off i get a flickering canvas.

I tried that, but the lag is still there unfortunately.
I guess it can't be helped then ;_; that's what I get for having gotten used to SAI!

thanks for your help everyone.

Just one more question, how come SAI (or PS) don't have that problem? I have a pretty decent GPU (GTX660) and CPU (i5 3570K), and from what I gather, it sounds like one of those is bottlenecking Krita . it sounds weird to me since those 2 other programs don't have a problem and the hardware should be capable enough (as it's relatively recent).
I'm not doubting what you say at all, it's just that I hope one day I won't have to deal with that lag, even if it happens only in specific circumstances.

Sai and Photoshop don't use your GPU.

did you try to set the cpu and gpu power governer to performance mode?
i have older hardware (gtx 470) and can set highest settings.
hm it might not be the gpu,
do you have the lag with other smothing options?
for the stabilizer reduce the distance value.

I have just tried it, I still have the lag.
and no, I only get that lag when zoomed in at ~1,131% and using specific rotation angles.


Ok then, I guess it can't be helped. thanks for the help everyone!