Recently quite a number of people in here(in my country) started to using Krita and I was very glad to see that, but also lots of them stopped using after a while and 99% of their reasons were 'it's too slow and laggy for my computer'. There were no issues with features, design, etc.

I'm sorry. Probably you guys are already sick of hearing this. But I think the 'speed' is one of the essential part that needs to be improved. I manually adjust many features by myself to optimize it, and I have x64 system on i7 quad core cpu and 16G of ram. But many people in general don't have & want to.

Just a thought.

Most of the "lag" seems to come from a too high precision setting in the standard brushes. The weird thing is that I _do not_ see lag not on Linux, not on OSX, not on any of my Windows systems... Maybe my perception is at fault, but the small amount of latency I see on the SP3, I see everywhere in the OS, so I'm blaming that on the n-trig bluetooth pen.

There are quite a few different variables that seem to be affecting speed and what causes lag, or the perception of lag.

1. Instant Preview. There can be a small lag after a brush stroke while it renders multiple versions of the canvas. This could probably be improved if we spent time looking at it more. Instant Preview is on by default.
2. Spacing. This is probably the biggest speedups. Increasing spacing too much though can reduce the quality. maybe these can be played with more
3. Precision would seem to help with some larger brushes. It doesn't make a big performance difference for all brushes, but it would definitely help some.
4. Brush Size - the larger the brush, the more lag that will happen as there are more pixels to calculate.

We don't really have anyone helping that is focusing on brush performance. All of the paid main objectives are with kickstarter goals, so that is what the developers are mostly focusing on. It has been improved quite a bit already, but still will have issues -- especially on older machines.

The amount of people that work on this project is probably far fewer than you would imagine.

Yes, people told us this, and we implemeted instant preview, and then it turned out people's graphics drivers hate them, and instant preview relies on working graphics drivers, so the quick brush was implemented.

Scott Petrovic's looking into what we can do about the default brushes to make them a bit more speedy, but I can tell you that this will not fully silence such complaints.

The fact is that Krita is a bit of an industrial workhorse, and it's very easy to do things that are probably somewhat ambitious. Combine this with that as a free open source software we made it free to download, and we get a lot of people that are so new to computers that they don't understand the meaning of stroking a 1000 pixel brush, or having an image of 15000 to 15000. So we're often trying to figure out with a lot of these reports whether the user belongs to this group or whether there's something serious going on.

Brush stroke logging could help a lot here(it is implemented), but we're very busy, so we haven't been able to generate a default test-suite or something alike.

Thanks for answering. I understood.

I remember you had plans to do Instant Preview smarter. How about add "Instant Preview cutoff" function to prevent lags with small sizes? Something similar to auto Precision but just disable Instant Preview if brush size smaller than X.
I must admit that I didn't use Instant Preview because of lags with small brushes but latest Krita don't have this problem. Feels like there is already some kind of performance detection (though sometimes it fails and big strokes renders slowly like Instant Preview disabled).

About Precision. How this thing work? I don't see any difference between stroke with precision 5 and precision 1, the only thing that hardly changes is brush performance.

Instant preview behaves in a very unpredictable way for me, and wouldn't use it for production at its current state.

In Krita you need to tweak things a bit more and adjust the program to your workflow, tweak the performance settings and the brushes, and understand how they work. Commercial programs like Ps and Painter are more polished, have fewer controls and work out-of-the-box.
I have an i7 with 12GB RAM and 2GB nvidia Graphics card. Certainly not a marvel of technology, but I get my day to day work with Krita done with minimal issues.

Some suggestions from my side concerning the slow performance of brushes (some are mentioned above as well):

- Smoothing: Try turning this off
- Spacing has a big impact. For thin-to-thick brushes, try tweaking the pressure curve in the spacing panel, so that more pressure (bigger size) = more spacing and vice versa.
- Patterns also have a big impact. If you absolutely need the stroke to have a texture, increase the spacing and try different kinds of brush tips until you find a good compromise.
- Use file layers! File layers do not impact performance, as far as I know, and they make your files more lightweight.
- Big brush is great. But sometimes you want a big brush with some more character to it. Try the bristle brushes: Some tweaking with the settings is necessary, but they are faster than the pixel brush engine.
- Restart the program every now and then.
- Check the performance settings.
- Keep the layer number as low as possible.
- Crop the document every now and then. Krita doesn't discard the strokes that go beyond canvas limits. Cropping the document to canvas size will get rid of these pixels and sometimes save you several MB of data.