Brush aliasing is wrong depending on brush size

[5argon]

*This is in fact Affinity Photo for macOS, mods please move it to that forum. But I am not sure it could be reproduced on pixel persona of Designer as well.

In this clip I show that the Basic brush with 100% opacity / flow / hardness, can produce unexpected aliasing depeding on brush size.

To suppliment the clip, for example, at this size there are parts with unaliased result similar to when using the Pixel Tool. Except that it happen randomly along the other edges that were correctly aliased.

At this size, it produce spacing artifacts in interval.

These are sizes that produce expected, consistent aliasing result.

 

Device : Wacom Intuos Pro M

Affinity Photo 1.7.2

[5argon]

New clip, sometimes you can see it is going to be wrong from the preview when adjusting brush size too.

[Sean P]

Hi 5argon,

Your brush sizes are non whole pixels, so you will get this aliasing behaviour, as the brush doesn't sit completely on a pixel boundary so is divided over 2 pixels. I would suggest you try looking into the Pixel Brush if you want completely hard edges.

[5argon]

4 hours ago, Sean P said:

Hi 5argon,

Your brush sizes are non whole pixels, so you will get this aliasing behaviour, as the brush doesn't sit completely on a pixel boundary so is divided over 2 pixels. I would suggest you try looking into the Pixel Brush if you want completely hard edges.

Hi. I get what you meant. What I want is actually non hard edge, a consistently aliased brush regardless of size. And all other software I used do not suffer from this problem no matter the size is whole pixel or not. For example, this clip is from Clip Studio Paint. It gives consistent aliasing edge and no sharp edge mixed in no matter what the size. And also, there is no size that produce the "upper repeating dotted pixel" like Affinity Photo. And when painting, I randomly get "bad brush" when scaling around the size. Brush size scaling is done arbitrarily by the painter and we should not have to concern whether the size is whole pixel or not.

 

[5argon]

Here, even with pixel brush, when scaling around (or even type in the number) I can get 2 version of 10.0 px and 16.0 px brush, where there is a repeating pixel problem and the one that looked fine.

[5argon]

Here, back to aliased brush. There is definitely some bad size on the whole number. And also I sometimes notice that even when in the one brush scaling, I could get a different result on the same number sometimes.

[Sean P]

Thanks for the videos. I see what you mean now - I've looked into this and can see what you mean. It appears to be that any round brush with an odd number size will give you those tips, I also noticed that even number brushes are also 1 pixel off! I shall get this passed on to development to be fixed. Note the number is the pixel value of the brush and each red square represents 1 pixel (although the image has been scaled up) to make a 'pixel ruler'.

In the meantime you can work around this by setting the Spacing of the brushes to around 4%.

Regarding the brush showing the different results is likely that the way your adjusting the brush hardness and size is creating decimal pixel values that are getting rounded up/down. I believe there is an improvement with development that the Pixel Brush should always increment in whole pixels when using Keyboard Shortcuts and also the Brush Size modifier you were using.

[5argon]

Hi, thank you. One other work around is to use 99% hardness, if someone stumbled on this thread and want to have some hot fix for hard brush that you do want some consistent aliasing.

7 minutes ago, Sean P said:

 

My intuition says that on the size like 9, 11, 13, and 15, even though there is that protruding pixel, when dragging horizontally/vertically that pixel should "smear" itself linearly instead of repeating in intervals. Is this a bug also? Or the brush works like a repeatedly firing gun instead of like the actual "brush"?

Top : Actual result of size 11 pixel brush

Bottom : Expected result of size 11 pixel brush

[Sean P]

6 minutes ago, 5argon said:

Or the brush works like a repeatedly firing gun instead of like the actual "brush"?

This is indeed how it works, it fires of 'nozzles' and when many of them are placed very close together it produces the brush effect. This can be see when you adjust the spacing value.