Artefacts using Natural Pencil brushes - Affinity Photo

[Art51]

When drawing with the Natural Pencil H, HB, 2B and to a lesser extent the 4B in Affinity Photo I'm finding digital/pixel artefacts when using my stylus to tilt for shading. It doesn't seem to happen with the stylus upright and so forming tighter lines. In my case, the resultant artefacts are not really noticeable until I zoom in but it seems unusual all the same and would not be pleasing if using the brush at a larger size.

I'm using 2019 MacBook Pro 16" intel i9 with 32GB RAM running Monterey 12.6.3

Hardware acceleration off and using OpenGL.

Using XP Pen Artist 24 QHD display tablet and also iPad as a graphics tablet via EasyCanvas app (the issue presents in both use cases).

This has been occurring in all versions of Affinity Photo 2 (currently running 2.4.1)

I usually draw in a 300dpi canvas at A1 size (7087x10004 pixels)

In the attached image, the lines on left (sans artefacts) are drawn with the stylus upright. The shading at right (with artefacts) is with stylus tilted to varying degree and pressure. In this case I was using Natural Pencil 2B brush at size of 12px but it happens regardless of the size of the brush.

[Callum]

Hi Art51,

Welcome to the forums!

I'm sorry to hear you are having issues with the Natural Pencil brushes, please could you tell me if this also occurs when just using a mouse or touchpad with your tablet disconnected? Please could you also tell me if this occurs when using an A4 document?

If possible could you also provide a sample document demonstrating this issue? You should be able to upload it to the following Dropbox link.

https://www.dropbox.com/request/CGDh88WoASAoqo3FvQ8l

Thanks
C

[Art51]

Hey Callum,

Thanks for getting back to me!

So the issue only presents when using the tilt function and is most noticeable when shading lightly (light pressure for a light stroke). I can't replicate this with the mouse or touch pad as there is no pressure sensitivity with either, let alone tilt.

I have uploaded two files to the dropbox, one is A1 at 300 dpi and the other is A4 at 300dpi. The artefacts are present in each file size (I created these new files for this experiment).

In each document I have shown examples of the strokes with each of the Natural Pencils (H, HB, 2B and 4B) in the default 32px size. The text is written with the stylus held upright/perpendicular to the screen and the shading above is with the stylus tilted and used from heavy to light pressure. The H pencil displays the most artefacts.

Hopefully there is a solution as I use the pencils, specifically the Natural 2B pencil, as my default brush for all my work. I'm able to work around the issue by smudging the artefacts (with the soft round brush) when they are noticeable in my work. I rarely use the pencil in large sizes where the issue is most noticeable.

Thanks again for having a look into this!

PS- Am SO happy to have found Affinity Photo. It's perfect for the kind of raster art I create! It's a pleasure to use and I really can't praise it enough, and I think I've tried all the others.

[Art51]

Here's a screenshot from the A4 file I uploaded.

[Art51]

I have been able to 'fix' this issue.

It seems the artefacts are only present when the Affinity Photo Performance settings are set to OpenGL, Hardware Acceleration is off and macOS is set to use Auto Graphics Switching in the power settings.

When I turn off Auto Graphics Switching and force macOS to use my GPU (AMD Radeon Pro 5600M) and turn on Metal and Hardware Acceleration, the pencils don't exhibit any artefacts (see image below). In fact, the pencil renders much more pleasingly. I wish I had discovered this sooner!

There must be some kind of Mercurial trickery going on when Affinity uses CPU for raster processes instead of communicating with the GPU.

The bonus of this discovery is that I have now found I can indeed use Metal and Hardware Acceleration and get great performance simply by turning off Auto Graphics Switching. I have been disappointed that I was suffering from poor performance with Metal and so have only used the CPU and OpenGL instead.

I bought the computer for its advanced GPU and now it seems I can make the most of it!

[Art51]

Okay, so after using these settings for a bit I'm finding the beachball starts to make an appearance during painting (using various brushes). It's starts intermittently after several minutes then becomes more frequent, like it's getting harder and harder for the system to keep on top it. So I restart Affinity Photo and begin again... same result, all is good for a while then the beachball begins again.

The Activity Monitor shows the Affinity Photo CPU and GPU usage flicking around. The app goes from the top of the list to the bottom as the beachball appears and disappears (it appears for about 5 secs following a stall when rendering a stroke). I wonder if the rendering is still switching from CPU to GPU and back for some reason...

I really hope this can be sorted out.

The Activity Monitor shows the usage as follows:

[NotMyFault]

Did you try RGB/16 instead of RGB/8 for document color format?

[Art51]

G'day NotMyFault,

No, I haven't tried that. I'm working in RGB/8.

As it happens, right now, I've been drawing for about 40mins without a single beachball. I had a feeling there was something being cleared by the system every few minutes and so as a test I changed my RAM usage and disk warning limits from 32GB to 22GB each and I also upped my Undo Limit to 500 (it was 131 beforehand).

I don't want to jinx things, but this seems to have worked. I reckon if it was going to stall or beachball it would have done it by now. If anything changes I'll post again. Hopefully this might be helpful to folk in a similar situation.

[NotMyFault]

2 hours ago, Art51 said:

No, I haven't tried that. I'm working in RGB/8.

In case of new issues, please give it a try. There are some old and occasionally reoccurring issues with RGB/8 (banding, wrong handling of 0 or 1 values) which are avoided in RGB/16. You can later export to RGB/8 if required.

[Art51]

Thanks so much for letting me know. That's very helpful, especially to know that I can export in the legacy format. Cheers mate!

[Art51]

@Callum@NotMyFault Just wanted to let you know I spent quite some time fiddling with RGB/16 to assess the painting/drawing experience and see if it is better than working with RGB/8.

When working in RGB/16 (A1 file at 300dpi) and Affinity Photo is set to use Metal and Hardware Acceleration (as noted in my comments above) my pencil strokes render really well (no artefacts) however the lag on strokes is very noticeable and eventually the beachball makes a prominent return and the system bogs down. It quickly becomes unusable.

However, when I switch the performance settings to use OpenGL or Metal and use the CPU only the RGB/16 painting experience is great! No lag at all AND there are no artefacts present in the pencil strokes like there were in the RGB/8 documents. So it seems the 16bit workspace solves the artefacts problem present in the 8bit format, just as NotMyFault suggested.

What a pity my GPU can't be used for 16bit raster painting/drawing! I can't seem to tweak settings any further to improve the situation.

Is there a reason my GPU Metal performance is so poor?

[Callum]

Hi Art51,

Apologies for missing your earlier reply to this thread, I'd like to ask a member of our QA team to give their opinion on this so I'll message them and then reply with any info I receive tomorrow

Thanks
C

[Art51]

@Callum Thanks for that mate!

Thought it might help to collate my findings from above into the following:

 

Natural Pencil artefacts present in RGB/8 document when:

• Using tilt function of stylus to shade (light strokes)
• Using CPU and OpenGL in performance settings
• GPU hardware acceleration is disabled

Natural Pencil artefacts NOT present in RGB/8 document when:

• Using tilt function of stylus to shade
• Using GPU Hardware Acceleration and Metal in performance settings

However, RGB/8 system performance suffers. To improve performance:

• macOS automatic graphics switching disabled
• Affinity Photo RAM usage and disc warning limit are lowered from maximum
• Undo limit raised

 

Natural Pencil artefacts NOT present in RGB/16 document when:

• Using tilt function of stylus to shade (light strokes)
• Using either CPU or GPU hardware acceleration
• Using either OpenGL or Metal
• macOS automatic graphics switching on or off

However, RGB/16 system performance suffers when using GPU hardware acceleration. To improve performance:

• Disable GPU hardware acceleration
• Use CPU and OpenGL or Metal in performance settings
• Affinity Photo RAM usage and disc warning limit are lowered from maximum
• Undo limit raised

 

 

[Art51]

@Callum Hey Callum, just wondering if you heard back from the QA team? Cheers.

[Callum]

On 5/29/2024 at 2:43 AM, Art51 said:

@Callum Hey Callum, just wondering if you heard back from the QA team? Cheers.

Unfortunately they have been quite busy recently with our 2.5 update which just released last week. I'll give one a nudge and see if they wouldn't mind sitting down and looking at this with me tomorrow.

[Art51]

7 hours ago, Callum said:

Unfortunately they have been quite busy recently with our 2.5 update which just released last week. I'll give one a nudge and see if they wouldn't mind sitting down and looking at this with me tomorrow.

No worries at all. Totally understand. There's no rush on my end as I've managed to rectify the problem in my specific workflow.

It might be of interest to your team as I'm unsure if it affects other brushes (and other things I've not discovered) thereby impacting the bulk of people painting in RGB/8 files using CPU and OpenGL.

Thanks again to you and all the crew for the fabulous work you do. I'm really enjoying creating with the programme. And well done with 2.5!

[Chris B]

Hey @Art51

I will try to investigate this next week when I can access similar hardware to yours. I haven't been able to reproduce this on my M1 MacBook so far. I will report back once I've tested this thoroughly. 

[Art51]

12 hours ago, Chris B said:

Hey @Art51

I will try to investigate this next week when I can access similar hardware to yours. I haven't been able to reproduce this on my M1 MacBook so far. I will report back once I've tested this thoroughly. 

Cheers Chris! Again, no rush mate.

[Chris B]

Hey @Art51 I think I have reproduced this.

On an 8bit document with OpenGL enabled and Metal Compute disabled I see similar to what you are seeing. Changing some of the brush settings can make the result vary slightly.

I was using our XP-Pen Artist 12 and tilting the pen with very light strokes seems to be the trigger for me also. Keeping the brush upright does not display the issue. It's almost like it's just choosing random pixels and filling them with a darker shade than the majority of the other pixels.

I will log this with dev and see if they have any idea what's happening.

[Art51]

Hiya @Chris B. Mmm, at first I was thinking it was pulling pixels from the base texture. But it really doesn't seem to be. Then I wondered if it was simply "stretching" the base texture to render the tilted shading.

I must say I haven't investigated other brushes to see if the issue presents elsewhere. Pencil work is where I use the most variety and subtlety so it stands out.

Many thanks for looking into it! I'm sure it will help others as well.

[Art51]

@Chris B I thought you'd like to see this...

After much experimenting with all manner of settings I believe I've solved the hardware acceleration issue.

I can now leave hardware acceleration ON and draw and paint in RGB/8 and RGB/16 documents regardless of layer count and file size. Previously I could only use hardware acceleration in documents with limited layers. Once the number of layers increased greatly, the beachball would appear.

However... it seems if the Music app is open and music is playing then Affinity Photo bogs down when the number of layers increases. I have no idea why playing mp3's with the Music app would cause an issue but there you go. I have tried numerous music player apps (VOX, IINA, Swinsian) and all have the same effect on Affinity Photo when using hardware acceleration.

My systems specs are as noted above, with the exception I'm now running macOS 12.7.5

[Chris B]

Hey @Art51

Thanks for the update. I've just tried this on a 100-layer document and it was fine for me but hardware can absolutely have an affect on it. I'll add this to the notes for the developers.

For what it's worth, in the past we have seen 3rd party apps interfere with ours and we have made fixes for these so hopefully something will come from this. Thanks again!

[Art51]

Cheers @Chris B

In case it helps matters at your end, my current document is 7087x10004 pixels at 300dpi (A1 with bleed). RGB/16 colour format with 77 layers at the moment. 3 of the top layers have blend modes (colour burn, overlay and multiply) that affect all the layers beneath.

The beachball doesn't present right away but after several minutes of laying down brushstrokes whilst music is playing. Once it appears it will continue to intervene, even if I'm not laying down brushstrokes.

If hardware acceleration is ON and music is ON the beachball appears.

If hardware acceleration is OFF and music is ON the beachball doesn't appear at all.

If hardware acceleration is ON and music is OFF the beachball doesn't appear at all.

No other apps (that I have identified) seem to affect performance.

The issue is consistently replicable.

Because you've logged it I won't create another bug report. I trust that's okay?

If you need any further info let me know. Thanks heaps for looking into it all!

[Chris B]

8 hours ago, Art51 said:

Because you've logged it I won't create another bug report. I trust that's okay?

 

It will not create a new one, no. We collect all the information and dump it into a single report. Even if a user reports a similar issue, it will just get tagged in an existing bug report if there is one. 

I can test this on some different hardware and update the bug report with anything I find - my MacBook Air seems to be handling it OK using the above test environment and using the initial file you sent us. 

 

[Art51]

That all sounds great to me. Thanks for taking the time to have a look into it all! It's very much appreciated.