Scarf Joint Seam leads to collisions with previously printed perimeters when Z hop is disabled

[fritzw]

Is there an existing issue for this problem?

• I have searched the existing issues

OrcaSlicer Version

2.2.0-RC and previous

Operating System (OS)

Linux, Windows

OS Version

Linux Mint 22, Windows 11

Additional system information

No response

Printer

irrelevant

How to reproduce

• Create project with multiple outer perimeters (e.g. with a hole).
• Set "Scarf Joint Seam" to "Countour and hole"
• Set Z hop to 0.0 in printer settings
• Inspect preview for travel moves that intersect previously printed perimeters

Actual results

• Print head travels diagonally down from the end of the previous scarf to the start of the next scarf.
• On the way there, it may intersect already printed perimeters, causing the print head to crash into these (marked in red on the screenshot).

Expected results

• Travel moves should never intersect previously printed lines.
• Print head should move to the X/Y coordinate of the next scarf first, and then move Z down to the start height.

Project file & Debug log uploads

orcaslicer_scarf_collision.3mf.zip

Checklist of files to include

• Log file
• Project file

Anything else?

A workaround is setting Z hop to a very small value like 0.01 (or maybe even smaller). This forces the travel move to be horizontal, but introduces additional (albeit tiny) Z moves: