Artifacts when using the smudge brush engine


To replicate the problem:
Create a new transparent layer; choosing any smudge brush (I'm using the Basic_circle_wet brush for this demo), reduce smudge length to 0.01 and increase colour rate to maximum; paint some random strokes on canvas changing either value or saturation; expecting the colour rate component to behave like the ordinary pixel brush at 100% opacity, I get some peculiar results:-

a. soft edges on a hard edged brush
b. the biggest problem is when changing value/saturation (WITHOUT CHANGING HUE), the soft edges of the previous strokes begin to fill-in until the soft edges are removed - sometimes shifting the hue towards blue
c. once a stroke has been completely filled-in, it is impossible to paint over any of the strokes unless on a new layer

The grey above the left eye was painted using the Mix_smear brush with black - smudge length 0.01, colour rate 1. And of course its not possible to paint over the grey unless on a new layer


This image shows what is happening around the edges. Created on a new layer, paint with airbrush then try painting with soft edge smudge brush e.g Bristles_wet.

To a certain extent, these problems occur with all the smudge brushes but its most apparent when using a soft edge at reduced smudge length. I'm using XP-Krita 2.8 but I noticed the problems on Ubuntu 12.04-Krita 2.7

Smudge brush engine was my fav so any help would be appreciated.

Hi.

Can you provide KRA file and brush PRESET you used?

The brushes I used were presets that ship with Krita 2.8 but with a single adjustment: reduce the smudge length to 0.01 in the 'edit brush settings' window - that is when the effect is most obvious

Brush used in first image 'Basic_circle_wet'
Brush used in second image 'Mix_smear'
Brush used in third image 'Bristles_wet'

The 2nd image can be replicated on ANY FLATTENED IMAGE just reduce the smudge length. For every stroke change saturation/value

For 1st and 2nd image IT IS IMPORTANT TO PAINT ON A NEW LAYER transparency is one of the things that creates those artifacts, again reduce the smudge length

I have the same colors distorting. I reported the bug here https://bugs.kde.org/show_bug.cgi?id=333227

thanks for the report.