Bug 498337

Summary:	Rotoscoping shape doesn't match selection.
Product:	[Applications] kdenlive	Reporter:	nuxttux
Component:	Video Effects & Transitions	Assignee:	Jean-Baptiste Mardelle <jb>
Status:	RESOLVED FIXED
Severity:	normal	CC:	balooii, fritzibaby
Priority:	NOR	Keywords:	triaged
Version First Reported In:	24.12.0
Target Milestone:	---
Platform:	Mint (Ubuntu based)
OS:	Linux
Latest Commit:	https://invent.kde.org/multimedia/kdenlive/-/commit/98a68e287a3cd75e7f33fc8129b4f4c35f5635a8	Version Fixed In:
Sentry Crash Report:
Attachments:	offset transform

Description nuxttux 2025-01-07 00:50:45 UTC

SUMMARY
Using the Rotoscoping effect, the selection outlines do not align with the shape/selection.
Applies to animated and static reotoscoping.

Note: When animated, if you move/wiggle the selection, the offset may disappear.

STEPS TO REPRODUCE
1. Enable monitor "Show Edit mode".
2. Add video clip to timeline + color clip on top.
3. Add rotoscoping effect to color clip.
4. Make a selection on color using rotoscoping.
5. Observe offset.

-OPTIONAL-

6. Animate rotoscoping, ~5 frames at a time ( 3- 4 keyframes).
7. Return to first keyframe - (everything aligns).
8. Jump to next keyframe - (notice offset).

OBSERVED RESULT
The (red) outline of the selection/shape does not align with the Rotoscoping selection outlines.

EXPECTED RESULT
The (red) outline of the Rotoscoping's selection should align with with the selection/shape

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 
KDE Frameworks Version: 6.9.0
Qt Version: 6.7.3

ADDITIONAL INFORMATION
In my experience, when animated - a simple wiggle of the selection restores the alignment.
Error seems to occur on smaller selections.
Error doesn't always occur.

Comment 1 emohr 2025-01-08 18:39:07 UTC

Thank you for reporting. I can confirm the issue. Following your steps. 

A small gap between the red rotoscoping out line and the color clip shape appear where the AV/clip shine through. In my case the color clip shape seems to be shifted 1 pixel downwards.
If you zoom into the monitor by one step the miss alignment is gone.

Comment 2 balooii 2025-04-14 18:29:14 UTC

Created attachment 180261 [details]
offset transform

Looks like its not specific to the rotoscope effect but more general. You get something similar when using transform and scale in a bit. Then you can see the offset on the red rectangle on the monitor.