grease pencil fast draw loses details in macOS #79425

System Information
Operating system: macOS 10.13.4
MacBook Pro (Retina, 13-inch, Early 2015)
Intel Iris Graphics 6100 1536 MB

Blender Version
2.83.3

Short description of error
From the grease pencil refactor demo, smoother drawing of fast strokes is achieved.

But when I tested, from the left drawing of the attached file, slow drawing produce smooth and accurate line. but the right drawing losses details in fast drawing and easily create corner. Is it an issue for macOS?
fast_stroke.blend

Comparison with drawing in Preview.app

Steps to redo:
New file > 2D animation
Scribble real fast.

Added subscriber: @ckim

Added subscriber: @iss

Are those corners created on start of stroke or on end? I am thinking, that this could be related to #78856

I have checked #78856, which I found some similarities and differences.

I try to draw some fast straight lines as #78856. I did notice some delay and result in similar shorter lines as #78856, but only about 20% of the lines got shortened, not as much as it is found in #78856.

I also noticed #78856 mentioned about large file size causing the delay, but I experience the loss of detail in fast draw starting from a new empty file. From the #78856 video that some description is written on the screen, which in my case, the same writing speed can't produce the same accuracy. A lot of detail is lost in the hand writing in my mac.

Finally, about the corners on the stroke, it is mostly created in the middle of the stroke, especially the curve line, I feel like it fails to track a complete fast draw, and is only able to capture a point in the middle which ends up creating a corner.

I hope this information helps!

Added subscriber: @donaldradams2

I'm seeing this exact issue on my mac as well. Only very slow drawing produces smooth lines, anything quicker has a bunch of angles in it.

I've tried posting a gif of the bug.

Here's a screenshot. The drawings on the right were drawn faster and have pointy corners in them for some reason. The smoother drawings were done very slowly.

I have an update on this. The bug is related to or affected by the screen resolution.

When on my laptop (specs in the post above) at the maximum resolution the bug is there. As I decrease the screen resolution, the circles/curves tend to be smoother. Also, when connected to an external LG 27" 4k monitor, the problem isn't there or is barely noticeable.

@ckim this might be a workaround for you until the team can address the underlying issue.

I tried to reproduce this issue on 4K, it is quite hard to produce consistent curves with consistent speed using mouse, so it is quite hard to triage.
Strokes that I make look relatively OK. Nothing that would raise any concern (apart from ocasional straight lines at start).

Thanks for the update.

The resolution of my macbook pro is 1440 x 900, it is not even the highest resolution, I did try to test it with the lowest resolution 1024 x 640, It does improve a lot (the line is acceptable, but the resolution is too small to work on), still the stroke is not as smooth as painting in Photoshop on the same mac.

I've just try out the new released 2.9, the issue is more or less the same. I hope it will be improved in a near future.

Added subscriber: @filedescriptor

Changed status from 'Needs Triage' to: 'Needs User Info'

Is this still an issue with the latest alpha from https://builder.blender.org/download/? Thanks.

Unfortunately this is still a problem in the Alpha release. I would say that it's even worse for me now. Here's a screenshot.

This really is a big problem for me. It makes grease pencil completely unusable for me and probably for other Mac users as well.

Changed status from 'Needs User Info' to: 'Needs Triage'

Changed status from 'Needs Triage' to: 'Confirmed'

Added subscriber: @PrototypeNM1

Just looking at the behavior, I would guess that some timeout or ring buffer overwrite mechanism is happening in OSX with tablet events, and Blender periodically doesn't get back to reading them fast enough. This would explain why changing screen resolution would change drawing performance when it otherwise shouldn't.

If there's no visual hitch in the program that indicates some operation in Blender is taking too long, then said mechanism isn't very forgiving. The fix would be to separate Blender event reading into it's own thread, so that it becomes very unlikely that any event isn't handled immediately.

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grease pencil fast draw loses details in macOS #79425