XP-Pen Artist Pressure Sensitivity Issues In Linux - Potential For Development

linux
Tags: #<Tag:0x00007fc07fcc4998>

#1

Please fill out the topic template below so we can help you faster.

Description of the Problem, or Question?

Depending on the brush used, normal functioning can be expected, or very light lines, or sometimes none at all. It should be noted that the tablet developers are committed to engaging the Linux community and have a driver in beta. They have been notified of these issues and will work on them when possible. Many of the same problems are present in Krita as well. Further, some of these issues can be temporarily solved in MyPaint by adjusting the pressure sensitivity/gain slider, but that also causes marks to become far too dark. Ideally brushes should work with default settings as they do with Wacom tablets. This is especially apparent when using Deevad’s “paint knife with smudging”. Very frustrating as it is my favourite brush. However, the knife in the “classic” set works just fine. Any idea why this is? I am not too familiar with making my own brushes, so I have no idea what is wrong. Most of the classic set works, along with some airbrushes or ink brushes in other sets, but not much else. As an additional note, I work at large sizes, as my work must be printed: 6500px x 6500px at 300 DPI.

I was not sure if this should be posted in the Developers Area, but I talked with the Support team at XP-Pen, and they seem reasonably open to working with other devs in the Linux community. If someone here in charge of development could reach out to them it may be worthwhile.

Basic System Details

MyPaint version:

1.2.0

Operating System + Version:

Ubuntu 18.04.1 LTS

Make and Model # of Graphic Tablet:

XP-Pen Artist 13.3

Please Tell Us How to Reproduce the Problem in Steps.

I simply selected the “paint knife with smudging” in set #2 and began to draw. No marks showed regardless of pressure applied. This happened with a number of other brushes across different sets. Setting the Gain slider to maximum caused marks to appear, but degraded the quality of what I wanted to achieve significantly, as lines would alternate between light and very dark. Some brushes worked as intended with default settings, but not very many.

Are there any Errors Popping Up? If so, paste the text in the area shown below.

[Paste Here]

For our guidelines to create a great user support ticket, please visit this wiki page at https://github.com/mypaint/mypaint/wiki/Reporting-Bugs#reporting-guidelines


#2

Pressure Gain is probably not what you want as it is a per-brush setting and it makes pressure have a non-linear response. That’s probably causing wild swings in the pressure making it hard to control.

First I would try Help–>Debug–>Test Input Devices
Press w/ the pen and note the values being reported. Do they seem smaller than they should be? Are they otherwise being reported in a normal way (pressing hard should reach some maximum like 1.0)
Try to make a note of these values:
Your Input % (estimate) vs mypaint reporting:
you: 0%. mypaint reports: __%
you: 50%. mypaint reports __%
you: 100%. mypaint reports __%

With these values in hand you might be able to set the global pressure mapping found in preferences:

In this example I’ve remapped the input pressure to 0-50% to 0-100%. Something like this might help your situation, but it’s hard to know unless you can do some of that testing and map out how your pressure is responding. Good luck!


#3

Thanks @briend. I conducted tests with my Wacom Intuos and my XP-Pen Artist tablet. the results are generally like this:

With Wacom, at 0% estimate, no pressure is reported, at 50% it reports about 0.3, or 30%, and at 100% 0.6-0.8. I assume this is normal, as it is the default I have been working with in the program for years without any adjustments. It is this kind of response I am aiming for with XP-Pen. However, that tablet reports nothing at 0%, may barely hit 0.1 at 50% and will not even hit 0.3 at 100%. As a point of reference, in my test I consider 0.3 - 0.4 a good sketching pressure, and use anything higher for darkened lines, and in many cases just go over light lines many times to avoid wear and tear on nibs. Also, as I mentioned before, a selection of brushes will behave normally, just as if I were using my Wacom tablet… would you have any idea why that is the case?

With all that said, how would I go about adjusting this pressure curve to set my XP-Pen tablet at similar values to my Intuos? Additionally, as I mentioned earlier, the driver released by the company is beta only, so things may improve in future, I consider the tablet a good alternative to a Cintiq in terms of build quality. Just putting that out there, as I saw a forum post some time ago about potential alternatives.

Thanks very much for your assistance!


#4

Interesting. Did you try my suggestion yet? It sounds like it would help a lot. You might get better results with this mapping:

Oh, regarding different brushes. The two you mentioned have very different pressure/opacity configurations with pressure. Take a look at Opacity and Opacity Multiply and view the pressure for both, and you’ll see what I mean. Fixing the global pressure mapping should pretty much fix everything I think!


#5

Thanks again @briend. Your suggestions did indeed help, although they did not quite fix everything. The brush I want to use seems very finicky, and even slight adjustments can change things quite a bit. I took a look at the standard knife as well, under the settings you mentioned, and I see what you mean. I believe I will stick to using that for the moment, to avoid unintentionally altering any settings that depend on the pressure as it is currently. I can live with making my under-layers with the brushes available. I will take your suggestions and perhaps apply them in Krita for additional layers if need be. As this is an issue across programs, I am wondering if this is a hardware issue, or simply the driver misbehaving. Thanks for your help!

As an additional note, I think it would be very helpful if in future someone could make some brush design tutorials. The whole system seems very complex. I absolutely love MyPaint, but the whole brush design thing is quite intimidating. For the most part I understand the curves concept, but even looking at some of the available brushes that have been created… how do you know exactly what affects what and how? Is it just trial and error and tinkering? I think the tool tips are a great start, but I think it would be of great use to everyone to see a professional like yourself or Deevad or Ramon design something from beginning to end. I did take a look at Ramon’s guide and think that is a great supplement as well, but seeing something done is a whole different experience. I know this has been asked before, but any chance in making photoshop brushes compatible with MyPaint? Krita allows brush tips, but does not import settings. Is something like that possible in future?


#6

Yeah I don’t expect it to be 100% with the drivers being so weird. I’m almost sure it isn’t a hardware problem, just the drivers. What might help even more is if you could map out the response in finer detail. That is, maybe your pen driver isn’t even giving you back a linear response. So you’d have to create a curve in the global pressure mapping to correct for that if it was the case. You might even just start with a curve and see if that helps. Try a convex and a concave and see if either of those help.

Brush editing can be pretty complicated. The best thing is to look at brushes that you like and figure out how they work; look for which settings and inputs are in effect. You might want to open the brush file (.myb) to easily see which settings are being used.

Then play with the settings with the instant preview turned on. I don’t think photoshop brushes will be compatible any time soon. Mypaint doesn’t even use custom stamps, every brush is based on little circles or ovals, basically. I agree we need a lot more tutorials though. I have a few on my youtube if you dig around. Here’s a flatbrush tutorial that also is a good overview of general brush editing. You’ll need an alpha build or compile from current git source for some of these settings, though.


#7

Thanks again. I will have to take a look at some of the brush files, as you suggested. I really like the video too, although I will have to watch it a few times to really get a handle on things. Once I am comfortable with that I’ll try messing with the pressure curves again; as I said, such wide ranging changes seem to effect the way some of the brushes with complex settings work quite a bit. In regards to installing an alpha build, I’m just paranoid about system stability, so I think I’ll wait on the next stable version. Thanks very much for all the useful information though, much appreciated!