Straight Bevel¶

Interactive modal bevel that places perpendicular cuts across the faces adjacent to each selected edge. At every ridge corner the cut is slid along the neighbouring (non-selected) edge so that the new edge sits at a fixed perpendicular distance from the original ridge, matching mesh.bevel(OFFSET, loop_slide=False) semantics. Two alternative modes (rounded percent bevel and flat in-face fan) are exposed from the same modal session.

bl_idname: iops.mesh_straight_bevel Mode: Edit Mesh Context: VIEW_3D Modal: yes HUD: yes

Overview¶

The operator targets corner ridges where Blender's stock bevel either bows the new edge into the face or refuses to maintain a true perpendicular offset on asymmetric corners. It collects every (corner vertex, adjacent face, neighbouring edge) triple along the selected chain, propagates a base offset around connected open chains so a single user value stays consistent across the whole selection, and drops perpendicular cuts on confirm.

The same modal session can be redirected into a Percent (rounded mesh.bevel SUPERELLIPSE) preview or a Flat Fan that rebuilds the corner ngon as a triangle fan whose boundary samples lie in a picked alignment-face plane. Use Flat Fan when the bevel terminates into a cap face and you need the boundary to remain coplanar with that cap.

Usage¶

Edit Mode on a mesh with at least one selected edge that has at least one adjacent face.
No default keymap binding — invoke via search (F3) or wire to a custom shortcut / pie.
Drag the mouse horizontally to scrub offset, or type a numeric value. Press B for rounded percent preview, F for flat fan. In flat fan mode, Q raycasts under the cursor to pick the alignment face for the nearest open-chain endpoint, W toggles boundary placement strategy. Confirm with LMB / Enter / Space; cancel with Esc / RMB.

Key	Action
`MouseMove`	Scrub offset horizontally
`Shift` + drag	Precise mode (0.1x sensitivity)
`Ctrl` + drag	Snap offset to 0.1 increments
`0`–`9` / Numpad	Type numeric offset
`.` / Numpad `.`	Decimal point in typed offset
`Backspace`	Delete last typed character
`B`	Toggle Percent bevel preview (mutually exclusive with Flat Fan)
`F`	Toggle Flat Fan preview (mutually exclusive with Percent)
`Q`	Flat Fan: raycast under cursor to bind alignment face to nearest endpoint
`W`	Flat Fan: toggle align mode (project / recompute)
`C`	Toggle post-bevel cleanup (limited dissolve on alignment-face planes)
`S`	Toggle snap cut endpoint to chain-endpoint vert
`WheelUp` / `WheelDown`	Adjust segments when Percent or Flat Fan is active (clamped 1..16); otherwise passes through to viewport
`MMB` / NDOF	Pass through to viewport navigation
`H`	Toggle help / HUD (handled by HUD overlay)
`LMB` / `Enter` / `Numpad Enter` / `Space`	Confirm
`Esc` / `RMB`	Cancel and restore initial offset

HUD¶

A dynamic HUD overlay (straight_bevel) shows current state for every toggle, with a paired help overlay listing all bindings. Live parameters:

Pct bevel (B) — bool, on when Percent mode is armed.
Flat fan (F) — bool, on when Flat Fan mode is armed.
Pct segs — int, active only while Percent is on.
Fan segs — int, active only while Flat Fan is on.
Align mode (W) — project or recompute, active only while Flat Fan is on.
Cleanup (C) — bool.
Snap to endpoint (S) — bool.

Viewport previews use the PREVIEW_LINE and PREVIEW_POINT theme roles. The straight cut preview is always drawn; Percent overlays a circular arc through the two cut points at each ridge corner; Flat Fan adds radial spokes from the corner vertex to every arc sample and, if an alignment face is bound at an endpoint, projects/resamples the arc into that face's plane.

Properties¶

Name	Type	Default	Description
`offset`	Float (DISTANCE)	0.05	Perpendicular distance from the ridge to the new cut. min 0.0, soft max 10.0, precision 4.
`mode`	Enum	`STRAIGHT`	Bevel variant: `STRAIGHT` (perpendicular cuts), `PCT` (rounded `mesh.bevel` SUPERELLIPSE), `FAN` (flat in-face triangle fan).
`pct_segments`	Int	16	Segments for Percent mode. Range 1..16.
`fan_segments`	Int	4	Segments for Flat Fan mode. Range 1..16.
`fan_align_mode`	Enum	`project`	Fan boundary placement: `project` (project bevel boundary verts onto picked face plane) or `recompute` (resample arc evenly in that plane).
`cleanup_mode`	Bool	False	Run a limited dissolve on geometry coplanar with the alignment faces after the bevel.
`snap_to_endpoint`	Bool	False	Split the boundary edge at the projection point and weld the cut endpoint into the new vertex, instead of only moving it geometrically.

Notes¶

Offset is hard-capped at modal start to the largest perpendicular value that still keeps every cut within 99% of its neighbour-edge length (accounting for per-vertex propagation correction); the cap is computed across every (vert, neighbour edge) pair, not just the deduped preview jobs, so multi-rail corners do not bypass it.
Open-chain interior vertices that sit at the centre of two collinear selected edges are detected and suppressed so the chain is treated as a single ridge. Each connected component propagates a per-vertex base correction along the chain so a single user offset produces consistent perpendicular spacing on bent chains.
Manual Q-picked alignment faces are not persisted to the redo panel; redo falls back to the auto-best candidate (the face whose normal is most parallel to the longest non-ridge edge at the endpoint, falling back to the ridge direction).
Wheel events are intercepted only while Percent or Flat Fan is active; otherwise they pass through so viewport zoom keeps working.
On cancel the original offset value is restored. Cancel and confirm both purge the cached bmesh / BMElement-keyed dicts so a later addon reload cannot resurrect freed mesh data through the redo stack.
Single registered class: IOPS_OT_straight_bevel. No companion Panel, Menu or PropertyGroup.