Bug 390897

Summary:	Bigger brush patters slow down stroke preview
Product:	[Applications] krita	Reporter:	Rytelier <rytelierofficial>
Component:	Usability	Assignee:	Krita Bugs <krita-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	halla
Priority:	NOR
Version:	4.0.0-beta.1
Target Milestone:	---
Platform:	Microsoft Windows
OS:	Microsoft Windows
Latest Commit:	https://commits.kde.org/krita/6bba5e0779d2d7639237359957793173b0f75a01	Version Fixed In:

Description Rytelier 2018-02-22 10:34:02 UTC

Using 4.0 Beta 2 (from  the news).

When I apply a texture to the stroke, it slows down the stroke preview causing adjusting brush settings to be laggy. Slowdowns start from 1024px pattern and it becomes slower when brush's pattern resolution is bigger.

Steps to reproduce:
- Create or import a pattern bigger than 1024px
- Apply this as a brush stroke texture
- Adjust carious brush settings to see the slowdown

Comment 1 Halla Rempt 2018-02-22 10:45:19 UTC

Sorry, but what do you expect? The bigger a texture, the more calculations need to happen, so the more time that takes. If you're using really big textures, you'll have to be a bit more patient: this will also affect the brush speed, of course.

And while we're always trying to make Krita faster by optimizing algorithms, it will always be true that if you're trying to manipulate more pixels at a time, then that will take more CPU and so more time: you cannot have instant infinity.

Comment 2 wolthera 2018-02-23 02:56:34 UTC

Git commit 6bba5e0779d2d7639237359957793173b0f75a01 by Wolthera van Hövell tot Westerflier.
Committed on 23/02/2018 at 02:56.
Pushed by woltherav into branch 'master'.

Live Brush Preview: Limit more paintop settings to reasonable sizes.

When having massive texture sizes, or massive brushes on the spraybrush,
the gui will freeze updue to live preview having trouble with all this.

This may seem like a case where the user shoots themselves in the foot
by picking too big sizes, but when using it, it isn't obvious that the
paintop preview is causing the GUI freeze, and it is more common to cause
these freezes by fatfingering controls than it is to cause freezes while
painting with a slow brush. Therefore let's limit these values to reasonable
sizes.

M  +49   -2    libs/ui/widgets/kis_preset_live_preview_view.cpp

https://commits.kde.org/krita/6bba5e0779d2d7639237359957793173b0f75a01

Comment 3 Rytelier 2018-03-04 14:28:44 UTC

I've checked latest nightly build after the fix and the issue is still here.
From what I've read in code changes, it lowers and freezes pattern's scale in temporary brush for preview (correct me if I'm wrong).
But scale property doesn't affect the preview speed at all, it's all depended on the pattern's resolution itself.

I don't know how programically would be it doable, but maybe limit preview's stroke texture's size by automatically cropping it? If it's not possible, then I suggest for option for user to disable the preview.